The Job of Diploma in Engineers is very tough in Bangladesh. Many Diploma Engineers did not qualify in the Public Service Commission (PSC) Examination lagging of their Subjects Objective Knowlwdge, Specially MCQ and their answers are drawback. I want to try here the EEE (Electrical and Electronic Engineering) objective questions and their answers. Here I Describe 53 Subjects Objective questions and their answers. The Engineers are benefited here . The Chapters are given below:

EEE Multiple choice Questions with Answers

1. Network Theorems

2. Synchronous Motors

3. Current Electricity

4. A.C. Fundamentals, Circuits & Circuit Theory

5. Circuit Theory

6. D.C. Generators

7. D.C. MOTORS

8. Transformers

9. Polyphase Induction Motors

10. Single Phase Induction Motors

11. Synchronous Motors

12. Rectifiers & Converters

13. Power Plant Engineering

14. Economics of Power Generation

15. Transmission & Distribution

16. Switchgear & Protection

Electrical Engineering Materials
CABLES
Electrical Machine Design
Measurement and Instrumentation
Control Systems
Electric Traction
Industrial Drives
Heating & Welding
Digital Electronics
Circuit Theorems and Conversions
Op-Amp Circuits
Analog Electronics
Semiconductor Theory
Semiconductor Diode
Transistors
Transistor Biasing
Single Stage Transistor Amplifiers
Multistage Transistor Amplifiers
Transistor Audio Power Amplifiers
Op Amp
Hybrid Parameters
Electronic Instruments
Integrated Circuits
Power Electronics
Silicon Controlled Rectifiers
Field Effect Transistors (Fet)
Solid State Switching Circuits
Regulated D.C. Power Supply
Modulation & Demodulation
Transistor Tuned Amplifiers
Oscillators
Parallel Circuits
Electrostatic
Magnetism And Electromagnetism
Magnetic Circuit
Electromagnetic Induction
Electrolysis And Storage Of Batteries

EEE Multiple choice Questions with Answers

Network Theorems

Kirchhoff s current law states that
(a) net current flow at the junction is positive
(b) Hebraic sum of the currents meeting at the junction is zero
(c) no current can leave the junction without some current entering it.
(d) total sum of currents meeting at the junction is zero
Ans: b
According to Kirchhoffs voltage law, the algebraic sum of all IR drops and e.m.fs. in any closed loop of a network is always
(a) negative
(b) positive
(c) determined by battery e.m.fs.
(d) zero
Ans: d
Kirchhoffs current law is applicable to only
(a) junction in a network
(b) closed loops in a network
(c) electric circuits
(d) electronic circuits
Ans: a
Kirchhoffs voltage law is related to
(a) junction currents
(b) battery e.m.fs.
(c) IR drops
(d) both (b) and (c)
(e) none of the above
Ans: d
Superposition theorem can be applied only to circuits having
(a) resistive elements
(b) passive elements
(c) non-linear elements
(d) linear bilateral elements
Ans: d
The concept on which Superposition theorem is based is
(a) reciprocity
(b) duality
(c) non-linearity
(d) linearity
Ans: d
Thevenin resistance Rth is found
(a) by removing voltage sources along with their internal resistances
(6) by short-circuiting the given two terminals
(c) between any two ‘open’ terminals
(d) between same open terminals as for Etk
Ans: d
An ideal voltage source should have
(a) large value of e.m.f.
(b) small value of e.m.f.
(c) zero source resistance
(d) infinite source resistance
Ans: c
For a voltage source
(a) terminal voltage is always lower than source e.m.f.
(b) terminal voltage cannot be higher than source e.m.f.
(c) the source e.m.f. and terminal voltage are equal
Ans: b
To determine the polarity of the voltage drop across a resistor, it is necessary to know
(a) value of current through the resistor
(b) direction of current through the resistor
(c) value of resistor
(d) e.m.fs. in the circuit
Ans: b
“Maximum power output is obtained from a network when the load resistance is equal to the output resistance of the network as seen from the terminals of the load”. The above statement is associated with
(a) Millman’s theorem
(b) Thevenin’s theorem
(c) Superposition theorem
(d) Maximum power transfer theorem
Ans: d
“Any number of current sources in parallel may be replaced by a single current source whose current is the algebraic sum of individual source currents and source resistance is the parallel combination of individual
source resistances”.
The above statement is associated with
(a) Thevenin’s theorem
(b) Millman’s theorem
(c) Maximum power transfer theorem
(d) None of the above
Ans: b
“In any linear bilateral network, if a source of e.m.f. E in any branch produces a current I in any other branch, then same e.m.f. acting in the second branch would produce the same current / in the first branch”.
The above statement is associated with
(a) compensation theorem
(b) superposition theorem
(c) reciprocity theorem
(d) none of the above
Ans: c
Which of the following is non-linear circuit parameter ?
(a) Inductance
(b) Condenser
(c) Wire wound resistor
(d) Transistor
Ans: a
A capacitor is generally a
(a) bilateral and active component
(b) active, passive, linear and nonlinear component
(c) linear and bilateral component
(d) non-linear and active component
Ans: c
“In any network containing more than one sources of e.m.f. the current in any branch is the algebraic sum of a number of individual fictitious currents (the number being equal to the number of sources of e.m.f.), each of which is due to separate action of each source of e.m.f., taken in order, when the remaining sources of e.m.f. are replaced by conductors, the resistances of which are equal to the internal resistances of the respective sources”.
The above statement is associated with
(a) Thevenin’s theorem
(b) Norton’s theorem
(c) Superposition theorem
(d) None of the above
Ans: c
Kirchhoff s law is applicable to
(a) passive networks only
(b) a.c. circuits only
(c) d.c. circuits only
(d) both a.c. as well d.c. circuits
Ans: d
Kirchhoff s law is not applicable to circuits with
(a) lumped parameters
(b) passive elements
(c) distributed parameters
(d) non-linear resistances
Ans: c
Kirchhoff s voltage law applies to circuits with
(a) nonlinear elements only
(b) linear elements only
(c) linear, non-linear, active and passive elements
(d) linear, non-linear, active, passive, time varying as wells as time-in-variant elements
Ans: d
The resistance LM will be
(a) 6.66 Q
(b) 12 Q
(c) 18Q
(d) 20Q
Ans: a
For high efficiency of transfer of power, internal resistance of the source should be
(a) equal to the load resistance
(b) less than the load resistance
(c) more than the load resistance
(d) none of the above
Ans: b
Efficiency of power transfer when maximum transfer of power c xerosis
(a) 100%
(b) 80%
(c) 75%
(d) 50%
Ans: d
If resistance across LM in Fig. 2.30 is 15 ohms, the value of R is
(a) 10 Q
(6) 20 Q
(c) 30 Q
(d) 40 Q
Ans: c
For maximum transfer of power, internal resistance of the source should be
(a) equal to load resistance
(b) less than the load resistance
(c) greater than the load resistance
(d) none of the above
Ans: a
If the energy is supplied from a source, whose resistance is 1 ohm, to a load of 100 ohms the source will be
(a) a voltage source
(b) a current source
(c) both of above
(d) none of the above
Ans: a
The circuit whose properties are same in either direction is known as
(a) unilateral circuit
(b) bilateral circuit
(c) irreversible circuit
(d) reversible circuit
Ans: b
In a series parallel circuit, any two resistances in the same current path must be in
(a) series with each other
(b) parallel with each other
(c) series with the voltage source.’
(d) parallel with the voltage source
Ans: a
The circuit has resistors, capacitors and semi-conductor diodes. The circuit will be known as
(a) non-linear circuit
(b) linear circuit
(c) bilateral circuit
(d) none of the above
Ans: a
A non-linear network does not satisfy
(a) superposition condition
(b) homogeneity condition
(c) both homogeneity as well as superposition condition
(d) homogeneity, superposition and associative condition
Ans: c
An ideal voltage source has
(a) zero internal resistance
(b) open circuit voltage equal to the voltage on full load
(c) terminal voltage in proportion to current
(d) terminal voltage in proportion to load
Ans: a
A network which contains one or more than one source of e.m.f. is known as
(a) linear network
(b) non-linear network
(c) passive network
(d) active network
Ans: c
The superposition theorem is applicable to
(a) linear, non-linear and time variant responses
(b) linear and non-linear resistors only
(c) linear responses only
(d) none of the above
Ans: c
Which of the following is not a nonlinear element ?
(a) Gas diode
(b) Heater coil
(c) Tunnel diode
(d) Electric arc
Ans:
Application of Norton’s theorem to a circuit yields
(a) equivalent current source and impedance in series
(6) equivalent current source and impedance in parallel
(c) equivalent impedance
(d) equivalent current source
Ans: a
Millman’s theorem yields
(a) equivalent resistance
(6) equivalent impedance
(c) equivalent voltage source
(d) equivalent voltage or current source
Ans: d
The superposition theorem is applicable to
(a) voltage only
(b) current “only
(c) both current and voltage
(d) current voltage and power
Ans: d
Between the branch voltages of a loop the Kirchhoff s voltage law imposes
(a) non-linear constraints
(b) linear constraints
(c) no constraints
(d) none of the above
Ans: b
A passive network is one which contains
(a) only variable resistances
(b) only some sources of e.m.f. in it
(c) only two sources of e.m.f. in it
(d) no source of e.m.f. in it
Ans: d
A terminal where three on more branches meet is known as
(a) node
(b) terminus
(c) combination
(d) anode
Ans: a
Which of the following is the passive element ?
(a) Capacitance
(b) Ideal current source
(c) Ideal voltage source
(d) All of the above
Ans: a
Which of the following is a bilateral element ?
(a) Constant current source
(b) Constant voltage source
(c) Capacitance
(d) None of the above
Ans: c
A closed path made by several branches of the network is known as
(a) branch
(b) loop
(c) circuit
(d) junction
Ans: b
A linear resistor having 0 < R < °o is a
(a) current controlled resistor
(6) voltage controlled resistor
(c) both current controlled and voltage controlled resistor
(d) none of the above
Ans: c
A star circuit has element of resistance R/2. The equivalent delta elements will be
(a) R/6
(b) fi?
(c) 2R
(d) 4R
Ans: b
A delta circuit has each element of value R/2. The equivalent elements of star circuit with be
(a) RIG
(b) R/3
(c) 2R
(d) 3R
Ans: a
In Thevenin’s theorem, to find Z
(a) all independent current sources are short circuited and independent voltage sources are open circuited
(b) all independent voltage sources are open circuited and all independent current sources are short circuited
(c) all independent voltage and current sources are short circuited
(d) all independent voltage sources are short circuited and all independent current sources are open circuited
Ans: d
While calculating Rth in Thevenin’s theorem and Norton equivalent
(a) all independent sources are made dead
(b) only current sources are made dead
(c) only voltage sources are made dead
(d) all voltage and current sources are made dead
Ans: a
The number of independent equations to solve a network is equal to
(a) the number of chords
(b) the number of branches
(c) sum of the number of branches and chords
(d) sum of number of branches, chords and nodes
Ans: a
The superposition theorem requires as many circuits to be solved as there are
(a) sources, nodes and meshes
(b) sources and nodes
(c) sources
(d) nodes
Ans: c
Choose the incorrect statement.
(a) A branch formed by the parallel connection of any resistor R and open circuit has the characteristic of an open circuit.
(b) A branch formed by the parallel connection of any resistor R and a short circuit has the characteristic of a short circuit.
(c) A branch formed by the series connection of any resistor R and an open circuit has the characteristic of an open circuit.
(d) A branch formed by the series connection of any resistor R and a short circuit has the characteristic of resistor R.
Ans: a

Synchronous

Synchronous motors are generally not self-starting because
(a) the direction of rotation is not fixed
(b) the direction of instantaneous torque reverses after half cycle
(c) startes cannot be used on these machines
(d) starting winding is not provided on the machines
Ans: b
In case one phase of a three-phase synchronous motor is short-circuited the motor will
(a) not start
(b) run at 2/3 of synchronous speed
(c) run with excessive vibrations
(d) take less than the rated load
Ans: a
A pony motor is basically a
(a) small induction motor
(b) D.C. series motor
(c) D.C. shunt motor
(d) double winding A.C./D.C. motor
Ans: a
A synchronous motor can develop synchronous torque
(a) when under loaded
(b) while over-excited
(c) only at synchronous speed
(d) below or above synchronous speed
Ans: c
A synchronous motor can be started by
(a) pony motor
(b) D.C. compound motor
(c) providing damper winding
(d) any of the above
Ans: d
A three-phase synchronous motor will have
(a) no slip-rings
(b) one slip-ring
(c) two slip-rings
(d) three slip-rings
Ans: c
Under which of the following conditions hunting of synchronous motor is likely to occur ?
(a) Periodic variation of load
(b) Over-excitation
(c) Over-loading for long periods
(d) Small and constant load
Ans: a
When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected
(a) the motor stops
(b) it runs as a reluctance motor at the same speed
(c) it runs as a reluctance motor at a lower speed
(d) none of the above
Ans: a
When V is the applied voltage, then the breakdown torque of a synchronous motor varies as
(a) V
(b) V312
(c) V2
(d) 1/V
Ans: a
The power developed by a synchronous motor will be maximum when the load angle is
(a) zero
(b) 45°
(c) 90°
(d) 120°
Ans: c
A synchronous motor can be used as a synchronous capacitor when it is
(a) under-loaded
(b) over-loaded
(c) under-excited
(d) over-excited
Ans: d
A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased
(a) power factor as well as armature current will decrease
(b) power factor as well as armature current will increase
(c) power factor will increase but armature current will decrease
(d) power factor will decrease and armature current will increase
Ans: d
Mostly, synchronous motors are of
(a) alternator type machines
(6) induction type machines
(c) salient pole type machines
(d) smooth cylindrical type machines
Ans: c
The synchronous motor is not inherently self-starting because
(a) the force required to accelerate the rotor to the synchronous speed in an instant is absent
(b) the starting device to accelerate the rotor to near synchronous speed is absent
(c) a rotating magnetic field does not have enough poles
(d) the rotating magnetic field is produced by only 50 Hz frequency currents
Ans: a
As the load is applied to a synchronous motor, the motor takes more armature current because
(a) the increased load has to take more current
(b) the rotor by shifting its phase backward causes motor to take more current
(c) the back e.m.f. decreases causing an increase in motor current
(d) the rotor strengthens the rotating field casuing more motor current
Ans: b
Synchronous motor always runs at
(a) the synchronous speed
(b) less than synchronous speed
(c) more than synchronous speed
(d) none of the above
Ans: a
An over-excited synchronous motor takes
(a) leading current
(b) lagging current
(c) both (a) and (b)
(d) none of the above
Ans: a
The working of a synchronous motor is similar to
(a) gear train arrangement
(b) transmission of mechancial power by shaft
(c) distribution transformer
(d) turbine
(e) none of the above
Ans: b
The minimum armature current of the synchronous motor corresponds to operation at
(a) zero power factor leading
(b) unity power factor
(c) 0.707 power factor lagging
(d) 0.707 power factor leading
Ans: b
In a synchronous motor, the magnitude of stator back e.m.f. £& depends on
(a) d.c. excitation only
(b) speed of the motor
(c) load on the motor
(d) both the speed and rotor flux
Ans: a
If load (or torque) angle of a 4-pole synchronous motor is 6° electrical, its value in mechanical degrees is
(a) 2
(b) 3
(c) 4
(d) 6
Ans: b
For V-curves for a synchronous motor the graph is drawn between
(a) field current and armature current
(b) terminal voltage and load factor
(c) power factor and field current
(d) armature current and power factor
Ans: a
The back e.m.f. of a synchronous motor depends on
(a) speed
(b) load
(c) load angle
(d) all of the above
Ans: c
A synchronous motor can operate at
(a) lagging power factor only
(6) leading power factor only
(c) unity power factor only
(d) lagging, leading and unity power factors
Ans: d
In a synchronous motor which loss varies with load ?
(a) Windage loss
(b) Bearing friction loss
(c) Copper loss
(d) Core loss
Ans: c
A synchronous motor can be made self starting by providing
(a) damper winding on rotor poles
(b) damper winding on stator
(c) damper winding on stator as well as rotor poles
(d) none of the above
Ans: d
The oscillations in a synchronous motor can be damped out by
(a) maintaining constant excitation
(b) running the motor on leading power factors
(c) providing damper bars in the rotor pole faces
(d) oscillations cannot be damped
Ans: c
The shaft of synchronous motor is made of
(a) mild steel
(b) chrome steel
(c) alnico
(d) stainless steel
Ans: a
When the field of a synchronous motor is under-excited, the power factor will be
(a) leading
(b) lagging
(c) unity
(d) zero
Ans: b
The speed regulation of a synchronous motor is always
(a) 1%
(b) 0.5%
(c) positive
(d) zero
Ans: d
The percentage slip in case of a synchronous motor is
(a) 1%
(b) 100%
(c) 0.5%
(d) zero
Ans: d
The operating speed of a synchronous motor can be changed to new fixed value by
(a) changing the load
(b) changing the supply voltage
(c) changing frequency
(d) using brakes
Ans: c
A synchronous motor will always stop when
(a) supply voltage fluctuates
(b) load in motor varies
(c) excitation winding gets disconnected
(d) supply voltage frequency changes9885859805
Ans: c
riunting in a synchronous motor takes place
(a) when supply voltage fluctuates
(b) when load varies
(c) when power factor is unity
(d) motor is under loaded
Ans: b
When load on an over-excited or under excited synchronous*motor is increased, rate of change of its armature current as compared with that of power factor is
(a) more
(b) less
(c) equal
(d) twice
Ans: b
The rotor copper losses, in a synchronous motor, are met by
(a) d.c. source
(b) armature input
(c) motor input
(d) supply lines
Ans: a
The maximum power developed in a synchronous motor occurs at a coupling angle of
(a) 30°
(b) 60°
(c) 90°
(d) 180°
Ans: c
When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor
(a) remains same as the original value
(b) decreases to half the original value
(c) tends to becomes zero
(d) increases to two times the original value
Ans: d
In which of the following motors the stator and rotor magnetic field rotate at the same speed ?
(a) Universal motor
(b) Synchronous motor
(c) Induction motor
(d) Reluctance motor
Ans: b
Synchronsizingpower of a synchronous machine is
(a) direcly proportional to the synchronous reactance
(6) inversely proportional to the synchronous reactance
(a) equal to the synchronous reactance
(d) none of the above
Ans: b
Synchronous motors are
(a) not-self starting
(b) self-starting
(c) essentially self-starting
(d) none of the above
Ans: a
The standard full-load power factor ratings for synchronous motors are
(a) zero or 0.8 leading
(b) unity or 0.8 lagging
(c) unity or 0.8 leading
(d) unity or zero
Ans: c
A synchronous motor running with normal excitation adjusts to load increases essentially by increase in
(a) back e.m.f.
(b) armature current
(c) power factor
(d) torque angle
Ans: b
A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because
(a) synchronous motor has no slip
(b) stator supply is not required to produce magnetic field
(c) mechanical load on the rotor remains constant
(d) synchronous motor has large airgap
Ans: b
A synchronous motor working at leading power factor can be used as
(a) voltage booster
(b) phase advancer
(c) noise generator
(d) mechanical synchronizer
Ans: b
Slip rings are usually made of
(a) carbon or graphite
(b) brass or steel
(c) silver or gold
(d) copper or aluminium
Ans: b
An over excited synchronous motor is used for
(a) fluctuating loads
(b) variable speed loads
(c) low torque loads
(d) power factor corrections
Ans: d
When the voltage applied to a synchronous motor is increased, which of the following will reduce ?
(a) Stator flux
(b) Pull in torque
(c) Both (a) and (b)
(d) None of the above
Ans: d
The efficiency of a properly designed synchronous motor will usually fall in range
(a) 60 to 70%
(6) 75 to 80%
(c) 85 to 95%
(d) 99 to 99.5%
Ans: c
To limit the operating temperature an electrical machine should have proper
(a) voltage rating
(b) current rating
(c) power factor
(d) speed
Ans: b
Slip-rings in a synchronous motor carry
(a) direct current
(b) alternating current
(c) no current
(d) all of the above
Ans: a
A synchronous machine with large air gap has
(a) a higher value of stability limit
(6) a small value of inherent regulation
(c) a higher synchronizing power which makes the machine less sensitive to load variations
(d) all of the above
Ans: d
The armature current of the synchronous motor has higher values for
(a) high excitation only
(b) low excitation only
(c) both (a) and (b)
(d) none of the above
Ans: c
In a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately
(a) one-third
(b) twice
(c) thrice
(d) six times
(e) nine times
Ans: c
The angle between the rotating stator flux and rotor poles is called _____ angle.
(a) torque
(b) obtuse
(c) synchronizing
(d) power factor
Ans: a
Which of the following methods is used to start a synchronous motor ?
(a) Damper winding
(b) Star-delta starter
(c) Damper winding in conjunction with star-delta starter
(d) Resistance starter in the armature circuit
Ans: c
When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop
(a) inductor motor torque
(b) induction generator torque
(c) synchronous motor torque
(d) d.c. motor toque
(e) none of the above
Ans: b
An important advantage of a synchronous motor over wound round induction motor is that
(a) its power factor may be varied at will
(b) its speed is independent of supply frequency
(c) its speed may be controlled more easily
(d) none of the above
Ans: a
The mechanical displacement of the rotor with respect to the stator, in polyphase multipolar synchronous motors running at full load, is of the order of
(a) zero degree
(b) two degrees
(c) five degrees
(d) ten degrees
Ans: c
Power factor of a synchronous motor is unity when
(a) the armature current is maximum
(b) the armature current is minimum
(c) the armature current is zero
(d) none of the above
Ans: b
Change of D.C. excitation of a synchronous motor changes
(a) applied voltage of the motor
(b) motor speed
(c) power factor of power drawn by the motor
(d) any of the above
(e) all of the above
Ans: c
While starting a synchronous motor by induction motor action, field winding is usually
(a) connected to D.C. supply
(b) short-circuited by low resistance
(c) kept open-circuited
(d) none of the above
Ans: b
Which of the following motors will be used in electric clocks ?
(a) D.C. shunt Motor
(b) D.C. series motor
(c) A.C. induction motor
(d) A.C. synchronous motor
Ans: d
If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor
(a) become more
(b) become less
(c) remain constant
(d) none of the above
Ans: b
A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will
(a) remain same
(b) go down
(c) improve
(d) none of the above
Ans: c
While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerting torque is produced by
(a) induction motor torque in field winding
(b) induction motor torque in damper winding
(c) eddy current and hysteresis torque in pole faces
(d) reHetance motor torque due to saliency of the rotor
(e) all of the above methods
Ans: e
Armature of a synchronous machine is
(a) of reducing number of slip rings on the rotor
(b) armature is associated with large power as compared to the field circuits
(c) of difficulty of providing high voltage insulation on rotor
(d) all of the above reasons
Ans: d
If excitation of a synchronous motor running with a constant load is decreased from its normal value, ignoring effects of armature reaction, it leads to
(a) increase in both armature current and power factor angle
(b) increase in back e.m.f. but decrease in armature current
(c) increase in both armature current and power factor which is lagging
(d) increase in torque angle but decrease in back e.m.f.
Ans: a
When a 3-phase synchronous generator is supplying a zero power factor lagging load, the armature field affects the main field in the following way
(a) augments it directly
(b) directly opposes it
(c) cross-magnetises it
(d) none of the above
Ans: b
Stability of a synchronous machine
(a) decreases with increase in its excitation
(b) increases with increase in its excitation
(c) remains unaffected with increase in excitation
(d) any of the above
Ans: b
The power factor of a synchronous motor is better than that of induction motor because
(a) stator supply is relieved of responsibility of producing magnetic field
(b) mechanical load on the motor can be adjusted
(c) synchronous motor runs at synchronous speed
(d) synchronous motor has large air gap
Ans: a
If in a synchronous motor, driving a given mechanical load and drawing current at a leading power factor from constant voltage supply its field excitation is increased, its power factor
(a) will become more
(b) will become less
(c) will remain unchanged
(d) none of the above.
Ans: b
A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because
(a) speed of the motor is reduced
(b) power factor is decreased
(c) Eb (back e.m.f.) becomes less than V (applied voltage)
(d) Er (net resultant voltage) in armature is increased
(e) none of the above
Ans: d
If one-phase of a 3-phase synchronous motor is short-circuited, motor
(a) will refuse to start
(b) will overheat in spots
(c) will not come upto speed
(d) will fail to pull into step
Ans: a
If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then
(a) it runs at a slower speed
(b) the motor stops
(c) it continues to run at the same speed
(d) it runs at a very high speed
Ans: b
In which of the following motors the stator and rotor fields rotate simultaneously ?
(a) D.C. motor
(b) Reluctance motor
(c) Universal motor
(d) Synchronous motor
(e) Induction motor
Ans: d
The speed of a synchronous motor
(a) increases as the load increases
(b) decreases as the load decreases
(c) always remains constant
(d) none of the above
Ans: c
A rotory converter can also be run as a
(a) d.c. shunt motor
(b) d.c. series motor
(c) d.c. compound motor
(d) induction motor
(e) synchronous motor
Ans: e
The maximum speed variation in a 3-phase synchronous motor is
(a) 10 per cent
(b) 6 per cent
(c) 4 per cent
(d) 2. per cent
(e) zero
Ans: e
Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor ?
(a) Phase to phase winding resistance
(b) Stator winding to earthed frame
(c) Rotor winding to earthed shaft
(d) All of the above
Ans: d
Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current ?
(a) High field current
(b) Low short circuit ratio
(c) High core losses
(d) Low field current
Ans: d

16.84. In a synchronous motor, the maximum power developed depends on all of the following except
(a) rotor excitation
(b) maximum value of coupling angle
(c) direction of rotation
(d) supply voltage
Ans: c

In a 3-phase synchronous motor, the negative phase sequence exists when the motor is
(a) supplied with unbalanced voltage
(b) under-loaded
(c) over-loaded
(d) none of the above
Ans: a
In a synchronous motor, damper windings are provided on
(a) stator frame
(b) rotor shaft
(c) pole faces
(d) none of the above
Ans: c
The induced e.m.f. in a synchronous motor working on leading power factor will be
(a) more than the supply voltage
(b) less than the supply voltage
(c) equal to the supply voltage
Ans: a
The effect of increasing the load on a synchronous motor running with normal excitation is to
(a) decrease both armature current and power factor
(6) decrease armature current but increase power factor
(c) increase armature current but decrease power factor
(d) increase both its armature current and power factor
Ans: c
The net armature voltage of a synchronous motor is equal to the
(a) vector sum of Eb and V
(b) arithmetic sum of Eb and V
(c) arithmetic difference of Eb and V
(d) vector difference of Eh and V
Ans: d
The ratio of starting torque to running torque in a synchronous motor is
(a) zero
(b) one
(c) two
(d) infinity
Ans: a
In a synchronous motor, the magnitude of stator back e.m.f. Eb depends on
(a) load on the motor
(b) d.c. excitation only
(c) both the speed and rotor flux
(d) none of the above
Ans: b
A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed
(a) the motor will stop
(b) the motor continue to run in the same direction
(c) the winding of the motor will burn
(d) the motor will run in the reverse direction
(e) none of the above
Ans: b
The magnitude of field flux in a 3-phase synchronous motor
(a) remains constant at all loads
(b) varies with speed
(c) varies with the load
(d) varies with power factor
Ans: a
The torque angle, in a synchronous motor, is the angle between
(a) the supply voltage and the back e.m.f.
(b) magnetising current and back e.m.f.
(c) the rotating stator flux and rotor poles
(d) none of the above
Ans: c
Hunting in a synchronous motor cannot be due to
(a) windage friction
(b) variable load
(c) variable frequency
(d) variable supply voltage
Ans: a
By which of the following methods the constant speed of a synchronous motor can be changed to new fixed value ?
(a) By changing the supply frequency
(b) By interchanging any two phases
(c) By changing the applied voltage
(d) By changing the load.
Ans: a
In a synchronous motor, V-curves represent relation between
(a) armature current and field current
(b) power factor and speed
(c) field current and speed
(d) field current and power factor
Ans: a
In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be
(a) 3000 r.p.m.
(b) 1500 r.p.m.
(c) 750 r.p.m.
(d) none of the above
Ans: b
A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have
(a) no change of power factor
(b) lagging power factor with over-excitation
(c) leading power factor with under-excitation
(d) leading power factor with over-excitation
Ans: d
Which of the following motors is non-self starting ?
(a) D.C. series motor
(b) synchronous motor
(c) Squirrel cage induction motor
(d) Wound round induction motor
Ans: b
In a synchronous motor it the back e.m.f. generated in the armature at noload is approximately equal to the applied voltage, then
(a) the motor is said to be fully loaded
(b) the torque generated is maximum
(c) the excitation is said to be zero per cent
(d) the excitation is said to be hundred per cent
Ans: d
In a synchronous motor, the damping winding is generally used to
(a) prevent hunting and provide the starting torque
(b) reduce the eddy currents
(c) provide starting torque only
(d) reduce noise level
(e) none of the above
Ans: a
If the field of a synchronous motor is underexcited, the power factor will be
(a) zero
(b) unity
(c) lagging
(d) leading
Ans: c
The back e.m.f. in the stator of a synchronous motor depends on
(a) number of poles
(b) flux density
(c) rotor speed
(d) rotor excitation
(e) none of the above
Ans: d
The maximum value of torque that a synchronous motor can develop without losing its synchronism, is known as
(a) slip torque
(b) pull-out torque
(c) breaking torque
(d) synchronising torque
Ans: d
In a synchronous motor, the armature current has large values for
(a) high excitation only
(b) low excitation only
(c) both high and low excitation
(d) none of the above
Ans: c
Which of the following losses, in a synchronous motor, does not vary with load?
(a) Windage loss
(b) Copper losses
(c) Any of the above
(d) None of the above
Ans: a
The size of a synchronous motor decreases with the increase in
(a) flux density
(b) horse power rating
(c) speed
(d) all of the above
Ans: a
Which of the following losses is not dissipated by the stator core surface in a synchronous motor ?
(a) Eddy current losses in the conductors
(b) Iron losses in the stator
(c) Copper losses in the slot portion of the conductors
(d) Windage losses
(e) None of the above
Ans: d
The duration of sudden snort-circuit test on a synchronous motor is usually about
(a) one hour
(b) one minute
(c) one second
(d) none of the above
Ans: c
The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as
(a) pull-up torque
(b) pull-in torque
(c) pull-out torque
(d) none of the above
Ans: b
A synchronous machine with low value of short-circuit ratio has
(a) lower stability limit
(6) high stability limit
(c) good speed regulation
(d) good voltage regulation
(e) none of the above
Ans: a
The construction of a synchronous motor resembles
(a) a series motor
(b) an induction motor
(c) an alternator
(d) a rotary converter
Ans: c
If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will
(a) stop
(b) run as induction motor
(c) function as static condenser
(d) burn with dense smoke
Ans: a
For power factor correction, synchronous motors operate at
(a) no-load and greatly over-excited fields
(b) no-load and under-excited fields
(c) normal load with minimum excitation
(d) normal load with zero excitation
Ans: a
The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as
(a) locked-rotor torque
(b) synchronous torque
(c) pull up torque
(d) reluctance torque
Ans: a
Exciters of synchronous machines are
(a) d.c. shunt machines
(b) d.c. series machines
(c) d.c. compound machines
(d) any of the above
Ans: a
The coupling angle or load angle of synchronous motor is defined as the angle between the
(a) rotor and stator teeth
(b) rotor and the stator poles of opposite polarity
(c) rotor and the stator poles of the same polarity
(d) none of the above
Ans: b
If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss
then
(a) the stator current will be zero
(b) the stator current will be very small
(c) the stator current will be very high
(d) the back e.m.f. will be more than the supply voltage
(e) none of the above
Ans: a

120 The armature current of the synchronous motor
(a) has large values for low excitation i niy
(b) has large values for high excitation only
(c) has large values for low and high excitation
(d) any of the above
Ans: c

The maximum power developed in a synchronous motor will depend on
(a) the rotor excitation only
(b) the supply voltage only
(c) the rotor excitation and supply volt-age both
(d) the rotor excitation, supply voltage and maximum value of coupling angle (90°)
(e) none of the above
Ans: d
A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as
(a) static condenser
(b) condenser
(c) synchronous condenser
(d) none of the above
Ans: c
A synchronous motor develops maximum power when load angle is
(a) 45°
(b) 60°
(c) 90°
(d) 120°
Ans: c
In a synchronous motor, the breakdown torque is
(a) directly proportional to applied voltage
(b) directly proportional to the square of the applied voltage
(c) inversely proportional to applied voltage
(d) none of the above
Ans: a

Current Electricity

The S.I. unit of power is
(a) Henry
(b) coulomb
(c) watt
(d) watt-hour
Ans: c
Electric pressure is also called
(a) resistance
(b) power
(c) voltage
(d) energy
Ans: c
The substances which have a large number of free electrons and offer a low resistance are called
(a) insulators
(b) inductors
(c) semi-conductors
(d) conductors
Ans: d
Out of the following which is not a poor conductor ?
(a) Cast iron
(b) Copper
(c) Carbon
(d) Tungsten
Ans: b
Out of the following which is an insulating material ?
(a) Copper
(b) Gold
(c) Silver
(d) Paper
Ans: d
The property of a conductor due to which it passes current is called
(a) resistance
(b) reluctance
(c) conductance
(d) inductance
Ans: c
Conductance is reciprocal of
(a) resistance
(b) inductance
(c) reluctance
(d) capacitance
Ans: a
The resistance of a conductor varies inversely as
(a) length
(6) area of cross-section
(c) temperature
(d) resistivity
Ans: b
With rise in temperature the resistance of pure metals
(a) increases
(b) decreases
(c) first increases and then decreases
(d) remains constant
Ans: a
With rise in temperature the resistance of semi-conductors
(a) decreases
(b) increases
(c) first increases and then decreases
(d) remains constant
Ans: a
The resistance of a copper wire 200 m long is 21 Q. If its thickness (diameter) is 0.44 mm, its specific resistance is around
(a) 1.2 x 10~8 Q-m
(b) 1.4 x 10~8 Q-m
(c) 1.6 x 10″”8 Q-m
(d) 1.8 x 10″8 Q-m
Ans: c
Three resistances of 10 ohms, 15 ohms and 30 ohms are connected in parallel.
The total resistance of the combination is
(a) 5 ohms
(b) 10 ohms
(c) 15 ohms
(d) 55 ohms
Ans:
An instrument which detects electric current is known as
(a) voltmeter
(b) rheostat
(c) wattmeter
(d) galvanometer
Ans: d
In a circuit a 33 Q resistor carries a current of 2 A. The voltage across the resistor is
(a) 33 V
(b) 66 v
(c) 80 V
(d) 132 V
Ans: b
A light bulb draws 300 mA when the voltage across it is 240 V. The resistance of the light bulb is
(a) 400 Q
(b) 600 Q
(c) 800 Q
(d) 1000 Q
Ans: c
The resistance of a parallel circuit consisting of two branches is 12 ohms. If the resistance of one branch is 18 ohms, what is the resistance of the other ?
(a) 18 Q
(b) 36 Q
(c) 48 Q
(d) 64 Q
Ans: b
Four wires of same material, the same cross-sectional area and the same length when connected in parallel give a resistance of 0.25 Q. If the same four wires are connected is series the effective resistance will be
(a) 1 Q
(b) 2 Q
(c) 3 Q
(d) 4 Q
Ans: d
A current of 16 amperes divides between two branches in parallel of resistances 8 ohms and 12 ohms respectively. The current in each branch is
(a) 6.4 A, 6.9 A
(b) 6.4 A, 9.6 A
(c) 4.6 A, 6.9 A
(d) 4.6 A, 9.6 A
Ans: b
Current velocity through a copper conductor is
(a) the same as propagation velocity of electric energy
(b) independent of current strength
(c) of the order of a few ^.s/m
(d) nearly 3 x 108 m/s
Ans: c
Which of the following material has nearly zero temperature co-efficient of resistance?
(a) Manganin
(b) Porcelain
(c) Carbon
(d) Copper
Ans: a
You have to replace 1500 Q resistor in radio. You have no 1500 Q resistor but have several 1000 Q ones which you would connect
(a) two in parallel
(b) two in parallel and one in series
(c) three in parallel
(d) three in series
Ans: b
Two resistors are said to be connected in series when
(a) same current passes in turn through both
(b) both carry the same value of current
(c) total current equals the sum of branch currents
(d) sum of IR drops equals the applied e.m.f.
Ans: a
Which of the following statement is true both for a series and a parallel D.C. circuit?
(a) Elements have individual currents
(b) Currents are additive
(c) Voltages are additive
(d) Power are additive
Ans: d
Which of the following materials has a negative temperature co-efficient of resistance?
(a) Copper
(b) Aluminum
(c) Carbon
(d) Brass
Ans: c
Ohm’s law is not applicable to
(a) vacuum tubes
(b) carbon resistors
(c) high voltage circuits
(d) circuits with low current densities
Ans: a
Which is the best conductor of electricity ?
(a) Iron
(b) Silver
(c) Copper
(d) Carbon
Ans: b
For which of the following ‘ampere second’ could be the unit ?
(a) Reluctance
(b) Charge
(c) Power
(d) Energy
Ans: b
All of the following are equivalent to watt except
(a) (amperes) ohm
(b) joules/sec.
(c) amperes x volts
(d) amperes/volt
Ans: d
A resistance having rating 10 ohms, 10 W is likely to be a
(a) metallic resistor
(b) carbon resistor
(c) wire wound resistor
(d) variable resistor
Ans: c
Which one of the following does not have negative temperature co-efficient ?
(a) Aluminium
(b) Paper
(c) Rubber
(d) Mica
Ans: a
Varistors are
(a) insulators
(6) non-linear resistors
(c) carbon resistors
(d) resistors with zero temperature coefficient
Ans: b
Insulating materials have the function of
(a) preventing a short circuit between conducting wires
(b) preventing an open circuit between the voltage source and the load
(c) conducting very large currents
(d) storing very high currents
Ans: b
The rating of a fuse wire is always expressed in
(a) ampere-hours
(b) ampere-volts
(c) kWh
(d) amperes
Ans: d
The minimum charge on an ion is
(a) equal to the atomic number of the atom
(b) equal to the charge of an electron
(c) equal to the charge of the number of electrons in an atom (#) zero
Ans: b
In a series circuit with unequal resistances
(a) the highest resistance has the most of the current through it
(b) the lowest resistance has the highest voltage drop
(c) the lowest resistance has the highest current
(d) the highest resistance has the highest voltage drop
Ans: d
The filament of an electric bulb is made of
(a) carbon
(b) aluminium
(c) tungsten
(d) nickel
Ans: c
A 3 Q resistor having 2 A current will dissipate the power of
(a) 2 watts
(b) 4 watts
(c) 6 watts
(d) 8 watts
Ans: c
Which of the following statement is true?
(a) A galvanometer with low resistance in parallel is a voltmeter
(b) A galvanometer with high resistance in parallel is a voltmeter
(c) A galvanometer with low resistance in series is an ammeter
(d) A galvanometer with high resistance in series is an ammeter
Ans: c
The resistance of a few meters of wire conductor in closed electrical circuit is
(a) practically zero
(b) low
(c) high
(d) very high
Ans: a
If a parallel circuit is opened in the main line, the current
(a) increases in the branch of the lowest resistance
(b) increases in each branch
(c) is zero in all branches
(d) is zero in the highest resistive branch
Ans: c
If a wire conductor of 0.2 ohm resistance is doubled in length, its resistance becomes
(a) 0.4 ohm
(b) 0.6 ohm
(c) 0.8 ohm
(d) 1.0 ohm
Ans: a
Three 60 W bulbs are in parallel across the 60 V power line. If one bulb burns open
(a) there will be heavy current in the main line
(b) rest of the two bulbs will not light
(c) all three bulbs will light
(d) the other two bulbs will light
Ans: d
The four bulbs of 40 W each are connected in series swift a battery across them, which of the following statement is true ?
(a) The current through each bulb in same
(b) The voltage across each bulb is not same
(c) The power dissipation in each bulb is not same
(d) None of the above
Ans: a
Two resistances Rl and Ri are connected in series across the voltage source where Rl>Ri. The largest drop will be across
(a) Rl
(b) Ri
(c) either Rl or Ri
(d) none of them
Ans: a
What will be energy used by the battery if the battery has to drive 6.28 x 1018 electrons with potential difference of 20 V across the terminal ?
(a) 5 joules
(b) 10 joules
(c) 15 joules
(d) 20 joules
Ans:
A closed switch has a resistance of
(a) zero
(b) about 50 ohms
(c) about 500 ohms
(d) infinity
Ans: a
The hot resistance of the bulb’s filament is higher than its cold resistance because the temperature co-efficient of the filament is
(a) zero
(b) negative
(c) positive
(d) about 2 ohms per degree
Ans: c
Heat in a conductor is produced on the passage of electric current due to
(a) reactance
(b) capacitance
(c) impedance
(d) resistance
Ans:
The insulation on a current carrying conductor is provided
(a) to prevent leakage of current
(b) to prevent shock
(c) both of above factors
(d) none of above factors
Ans: c
The thickness of insulation provided on the conductor depends on
(a) the magnitude of voltage on the conductor
(b) the magnitude of current flowing through it
(c) both (a) and (b)
(d) none of the above
Ans: a
Which of the following quantities remain the same in all parts of a series circuit ?
(a) Voltage
(b) Current
(c) Power
(d) Resistance
Ans: b
A 40 W bulb is connected in series with a room heater. If now 40 W bulb is replaced by 100 W bulb, the heater output will
(a) decrease
(b) increase
(c) remain same
(d) heater will burn out
Ans: b
In an electric kettle water boils in 10 m minutes. It is required to boil the boiler in 15 minutes, using same supply mains
(a) length of heating element should be decreased
(b) length of heating element should be increased
(c) length of heating element has no effect on heating if water
(d) none of the above
Ans: a
An electric filament bulb can be worked from
(a) D.C. supply only
(b) A.C. supply only
(c) Battery supply only
(d) All above
Ans: d
Resistance of a tungsten lamp as applied voltage increases
(a) decreases
(b) increases
(c) remains same
(d) none of the above
Ans: b
Electric current passing through the circuit produces
(a) magnetic effect
(b) luminous effect
(c) thermal effect
(d) chemical effect
(e) all above effects
Ans: c
Resistance of a material always decreases if
(a) temperature of material is decreased
(6) temperature of material is increased
(c) number of free electrons available become more
(d) none of the above is correct
Ans: c
If the efficiency of a machine is to be high, what should be low ?
(a) Input power
(b) Losses
(c) True component of power
(d) kWh consumed
(e) Ratio of output to input
Ans: b
When electric current passes through a metallic conductor, its temperature rises. This is due to
(a) collisions between conduction electrons and atoms
(b) the release of conduction electrons from parent atoms
(c) mutual collisions between metal atoms
(d) mutual collisions between conducting electrons
Ans: a
Two bulbs of 500 W and 200 W rated at 250 V will have resistance ratio as
(a) 4 : 25
(b) 25 : 4
(c) 2 : 5
(d) 5 : 2
Ans: c
A glass rod when rubbed with silk cloth is charged because
(a) it takes in proton
(b) its atoms are removed
(c) it gives away electrons
(d) it gives away positive charge
Ans: c
Whether circuit may be AC. or D.C. one, following is most effective in reducing the magnitude of the current.
(a) Reactor
(b) Capacitor
(c) Inductor
(d) Resistor
Ans: d
It becomes more difficult to remove
(a) any electron from the orbit
(6) first electron from the orbit
(c) second electron from the orbit
(d) third electron from the orbit
Ans: d
When one leg of parallel circuit is opened out the total current will
(a) reduce
(b) increase
(c) decrease
(d) become zero
Ans: c
In a lamp load when more than one lamp are switched on the total resistance of the load
(a) increases
(b) decreases
(c) remains same
(d) none of the above
Ans: b
Two lamps 100 W and 40 W are connected in series across 230 V (alternating).
Which of the following statement is correct ?
(a) 100 W lamp will glow brighter
(b) 40 W lamp will glow brighter
(c) Both lamps will glow equally bright
(d) 40 W lamp will fuse
Ans: b
Resistance of 220 V, 100 W lamp will be
(a) 4.84 Q
(b) 48.4 Q
(c) 484 ft
(d) 4840 Q
Ans: c
In the case of direct current
(a) magnitude and direction of current remains constant
(b) magnitude and direction of current changes with time
(c) magnitude of current changes with time
(d) magnitude of current remains constant
Ans: a
When electric current passes through a bucket full of water, lot of bubbling is observed. This suggests that the type of supply is
(a) A.C.
(b) D.C.
(c) any of above two
(d) none of the above
Ans: b
Resistance of carbon filament lamp as the applied voltage increases.
(a) increases
(b) decreases
(c) remains same
(d) none of the above
Ans: b
Bulbs in street lighting are all connected in
(a) parallel
(b) series
(c) series-parallel
(d) end-to-end
Ans: a
For testing appliances, the wattage of test lamp should be
(a) very low
(b) low
(c) high
(d) any value
Ans: c
Switching of a lamp in house produces noise in the radio. This is because switching operation produces
(a) arcs across separating contacts
(b) mechanical noise of high intensity
(c) both mechanical noise and arc between contacts
(d) none of the above
Ans: a
Sparking occurs when a load is switched off because the circuit has high
(a) resistance
(b) inductance
(c) capacitance
(d) impedance
Ans: b
Copper wire of certain length and resistance is drawn out to three times its length without change in volume, the new resistance of wire becomes
(a) 1/9 times
(b) 3 times
(e) 9 times
(d) unchanged
Ans: c
When resistance element of a heater fuses and then we reconnect it after removing a portion of it, the power of the heater will
(a) decrease
(b) increase
(c) remain constant
(d) none of the above
Ans: b
A field of force can exist only between
(a) two molecules
(b) two ions
(c) two atoms
(d) two metal particles
Ans: b
A substance whose molecules consist of dissimilar atoms is called
(a) semi-conductor
(b) super-conducto
(c) compound
(d) insulator
Ans: c
International ohm is defined in terms of the resistance of
(a) a column of mercury
(b) a cube of carbon
(c) a cube of copper
(d) the unit length of wire
Ans: a
Three identical resistors are first connected in parallel and then in series.
The resultant resistance of the first combination to the second will be
(a) 9 times
(b) 1/9 times
(c) 1/3 times
(d) 3 times
Ans: b
Which method can be used for absolute measurement of resistances ?
(a) Lorentz method
(b) Releigh method
(c) Ohm’s law method
(d) Wheatstone bridge method
Ans: d
Three 6 ohm resistors are connected to form a triangle. What is the resistance between any two corners ?
(a) 3/2 Q
(b 6 Q
(c) 4 Q
(d) 8/3 Q
Ans: c
Ohm’s law is not applicable to
(a) semi-conductors
(b) D.C. circuits
(c) small resistors
(d) high currents
Ans: a
Two copper conductors have equal length. The cross-sectional area of one conductor is four times that of the other. If the conductor having smaller cross-sectional area has a resistance of 40 ohms the resistance of other conductor will be
(a) 160 ohms
(b) 80 ohms
(c) 20 ohms
(d) 10 ohms
Ans: d
A nichrome wire used as a heater coil has the resistance of 2 £2/m. For a heater of 1 kW at 200 V, the length of wire required will be
(a) 80 m
(b) 60 m
(c) 40 m
(d) 20 m
Ans: a
Temperature co-efficient of resistance is expressed in terms of
(a) ohms/°C
(b) mhos/ohm°C
(e) ohms/ohm°C
(d) mhos/°C
Ans: c
Which of the following materials has the least resistivity ?
(a) Zinc
(b) Lead
(c) Mercury
(d) Copper
Ans:
When current flows through heater coil it glows but supply wiring does not glow because
(a) current through supply line flows at slower speed
(b) supply wiring is covered with insulation layer
(c) resistance of heater coil is more than the supply wires
(d) supply wires are made of superior material
Ans: c
The condition for the validity under Ohm’s law is that
(a) resistance must be uniform
(b) current should be proportional to the size of the resistance
(c) resistance must be wire wound type
(d) temperature at positive end should be more than the temperature at negative end
Ans: a
Which of the following statement is correct ?
(a) A semi-conductor is a material whose conductivity is same as between that of a conductor and an insulator
(b) A semi-conductor is a material which has conductivity having average value of conductivity of metal and insulator
(c) A semi-conductor is one which con¬ducts only half of the applied voltage
(d) A semi-conductor is a material made of alternate layers of conducting material and insulator
Ans: a
A rheostat differs from potentiometer in the respect that it
(a) has lower wattage rating
(b) has higher wattage rating
(c) has large number of turns
(d) offers large number of tapping
Ans: b
The weight of an aluminium conductor as compared to a copper conductor of identical cross-section, for the same electrical resistance, is
(a) 50%
(b) 60%
(c) 100%
(d) 150%
Ans: a
An open resistor, when checked with an ohm-meter reads
(a) zero
(b) infinite
(c) high but within tolerance
(d) low but not zero
Ans: b
are the materials having electrical conductivity much less than most of the metals but much greater than that of typical insulators.
(a) Varistors
(b) Thermistor
(c) Semi-conductors
(d) Variable resistors
Ans: c
All good conductors have high
(a) conductance
(b) resistance
(c) reluctance
(d) thermal conductivity
Ans: a
Voltage dependent resistors are usually made from
(a) charcoal
(b) silicon carbide
(c) nichrome
(d) graphite
Ans: c
Voltage dependent resistors are used
(a) for inductive circuits
(6) to supress surges
(c) as heating elements
(d) as current stabilizers
Ans: b
The ratio of mass of proton to that of electron is nearly
(a) 1840
(b) 1840
(c) 30
(d) 4
Ans: a
The number of electrons in the outer most orbit of carbon atom is
(a) 3
(b) 4
(c) 6
(d) 7
Ans: b
With three resistances connected in parallel, if each dissipates 20 W the total power supplied by the voltage source equals
(a) 10 W
(b) 20 W
(c) 40 W
(d) 60 W
Ans: d
A thermistor has
(a) positive temperature coefficient
(b) negative temperature coefficient
(c) zero temperature coefficient
(d) variable temperature coefficient
Ans: c
If/, R and t are the current, resistance and time respectively, then according to Joule’s law heat produced will be proportional to
(a) I2Rt
(b) I2Rf
(c) I2R2t
(d) I2R2t*
Ans: a
Nichrome wire is an alloy of
(a) lead and zinc
(b) chromium and vanadium
(c) nickel and chromium
(d) copper and silver
Ans: c
When a voltage of one volt is applied, a circuit allows one micro ampere current to flow through it. The conductance of the circuit is
(a) 1 n-mho
(b) 106 mho
(c) 1 milli-mho
(d) none of the above
Ans: a
Which of the following can have negative temperature coefficient ?
(a) Compounds of silver
(6) Liquid metals
(c) Metallic alloys
(d) Electrolytes
Ans: d
Conductance : mho ::
(a) resistance : ohm
(b) capacitance : henry
(c) inductance : farad
(d) lumen : steradian
Ans: a
1 angstrom is equal to
(a) 10-8 mm
(6) 10″6 cm
(c) 10″10 m
(d) 10~14 m
Ans: c
One newton meter is same as
(a) one watt
(b) one joule
(c) five joules
(d) one joule second
Ans: b

A.C. Fundamentals, Circuits & Circuit Theory

A sine wave has a frequency of 50 Hz. Its angular frequency is _______ radian/second.
(a) 100 n
(b) 50 jt
(c) 25 JT
(d) 5 n
Ans: a
The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance becomes_____ohms.
(a) 2.5
(b) 5
(c) 10
(d) 15
Ans: c
The period of a wave is
(a) the same as frequency
(6) time required to complete one cycle
(c) expressed in amperes
(d) none of the above
Ans: b
The form factor is the ratio of
(a) peak value to r.m.s. value
(6) r.m.s. value to average value
(c) average value to r.m.s. value
(d) none of the above
Ans: b
The period of a sine wave is _____ seconds.
Its frequency is
(a) 20 Hz
(b) 30 Hz
(c) 40 Hz
(d) 50 Hz
Ans: d
A heater is rated as 230 V, 10 kW, A.C. The value 230 V refers to
(a) average voltage
(b) r.m.s. voltage
(c) peak voltage
(d) none of the above
Ans: b
If two sinusoids of the same frequency but of different amplitudes and phase angles are subtracted, the resultant is
(a) a sinusoid of the same frequency
(b) a sinusoid of half the original frequency
(c) a sinusoid of double the frequency
(d) not a sinusoid
Ans: a
The peak value of a sine wave is 200 V. Its average value is
(a) 127.4 V
(b) 141.4 V
(c) 282.8 V
(d)200V
Ans: a
If two sine waves of the same frequency have a phase difference of JT radians, then
(a) both will reach their minimum values at the same instant
(b) both will reach their maximum values at the same instant
(c) when one wave reaches its maxi¬mum value, the other will reach its minimum value
(d) none of the above
Ans: c
The voltage of domestic supply is 220V. This figure represents
(a) mean value
(b) r.m.s. value
(c) peak value
(d) average value
Ans: a
Two waves of the same frequency have opposite phase when the phase angle between them is
(a) 360°
(b) 180°
(c) 90°
(d) 0°
Ans: b
The power consumed in a circuit element will be least when the phase difference between the current and voltage is
(a) 180″
(b) 90°
(c) 60°
(d) 0°
Ans: b
The r.m.s. value and mean value is the same in the case of
(a) triangular wave
(6) sine wave
(c) square wave
(d) half wave rectified sine wave
Ans: c
For the same peak value which of the following wave will ‘have the highest r.m.s. value ?
(a) square wave
(b) half wave rectified sine wave
(c) triangular wave
(d) sine wave
Ans: a
For the same peak value, which of the following wave has the least mean value ?
(a) half wave rectified sine wave
(b) triangular wave
(c) sine wave
(d) square wave
Ans: a
For a sine wave with peak value Imax the r.m.s. value is
(a) 0.5 Imax
(b) 0.707
(c) 0.9
(d) 1.414 Lmax
Ans: b
Form Factor is the ratio of
(a) average value/r.m.s. value
(b) average value/peak value
(e) r.m.s. value/average value
(d) r.m.s. value/peak value
Ans: c
Form factor for a sine wave is
(a) 1.414
(b) 0.707
(c) 1.11
(d) 0.637
Ans: c
For a sine wave with peak value Emax______8.30. the average value is
(a) 0.636 Emax
(b) 0.707 Emax
(c) 0.434 EWc
(d) lAUEmax
Ans: a
For a frequency of 200 Hz, the time period will be
(a) 0.05 s
(b) 0.005 s
(c) 0.0005 s
(d) 0.5 s
Ans: b
The phase difference between voltage and current wave through a circuit element is given as 30°. The essential condition is that
(a) both waves must have same frequency
(b) both waves must have identical peak values
(c) both waves must have zero value at the same time
(d) none of the above
Ans: a
The r.m.s. value of a sinusoidal A.C. current is equal to its value at an angle of______degrees.
(a) 90
(b) 60
(c) 45
(d) 30
Ans: c
Capacitive reactance is more when
(a) capacitance is less and frequency of supply is less
(b) capacitance is less and frequency of supply is more
(c) capacitance is more and frequency of supply is less
(d) capacitance is more and frequency of supply is more
Ans: a
In a series resonant circuit, the impedance of the circuit is
(a) minimum
(b) maximum
(c) zero
(d) none of the above
Ans: a
Power factor of an electrical circuit is equal to
(a) R/Z
(b) cosine of phase angle difference be-tween current and voltage
(c) kW/kVA
(d) ratio of useful current to total cur¬rent Iw/I
(e) all above
Ans: e
The best place to install a capacitor is
(a) very near to inductive load
(b) across the terminals of the inductive load
(c) far away from the inductive load
(d) any where
Ans: b
Poor power factor
(a) reduces load handling capability of electrical system
(b) results in more power losses in the electrical system
(c) overloads alternators, transformers and distribution lines
(d) results in more voltage drop in the line
(e) results in all above
Ans: e
Capacitors for power factor correction are rated in
(a) kW
(b) kVA
(c) kV
(d) kVAR
Ans: d
In series resonant circuit, increasing inductance to its twice value and reducing capacitance to its half value
(a) will change the maximum value of current at resonance
(6) will change the resonance frequency
(c) will change the impedance at resonance frequency
(d) will increase the selectivity of the circuit
Ans: d
Pure inductive circuit
(a) consumes some power on average
(b) does not take power at all from a line
(c) takes power from the line during some part of the cycle and then returns back to it during other part of the cycle
(d) none of the above
Ans: c
Inductance affects the direct current flow
(a) only at the time of turning off
(b) only at the time of turning on
(c) at the time of turning on and off
(d) at all the time of operation
Ans: c
Inductance of a coil Varies
(a) directly as the cross-sectional area of magnetic core
(b) directly as square of number of turns
(c) directly as the permeability of the core
(d) inversely as the length of the iron path
(e) as (a) to (d)
Ans: e
All the rules and laws of D.C. circuit also apply to A.C. circuit containing
(a) capacitance only
(b) inductance only
(c) resistance only
(d) all above
Ans: c
Time constant of an inductive circuit
(a) increases with increase of inductance and decrease of resistance
(b) increases with the increase of inductance and the increase of resistance
(c) increases with decrease of inductance and decrease of resistance
(d) increases with decrease of inductance and increase of resistance
Ans: a
Power factor of an inductive circuit is usually improved by connecting capacitor to it in
(a) parallel
(b) series
(c) either (a) or (b)
(d) none of the above
Ans: a
In a highly capacitive circuit the
(a) apparent power is equal to the actual power
(b) reactive power is more than the apparent power
(c) reactive power is more than the actual power
(d) actual power is more than its reactive power
Ans: c
Power factor of the following circuit will be zero
(a) resistance
(b) inductance
(c) capacitance
(d) both (b) and (c)
Ans: d
Power factor of the following circuit will be unity
(a) inductance
(b) capacitance
(c) resistance
(d) both (a) and (b)
Ans: c
Power factor of the system is kept high
(a) to reduce line losses
(b) to maximise the utilization of the capacities of generators, lines and transformers
(c) to reduce voltage regulation of the line
(d) due to all above reasons
Ans: d
The time constant of the capacitance circuit is defined as the time during which voltage
(a) falls to 36.8% of its final steady value
(b) rises to 38.6% of its final steady value
(c) rises to 63.2% of its final steady value
(d) none of the above
Ans: c
In a loss-free R-L-C circuit the transient current is
(a) oscillating
(b) square wave
(c) sinusoidal
(d) non-oscillating
Ans: c
The r.m.s. value of alternating current is given by steady (D.C.) current which when flowing through a given circuit for a given time produces
(a) the more heat than produced by A.C. when flowing through the same circuit
(b) the same heat as produced by A.C. when flowing through the same circuit
(c) the less heat than produced by A.C. flowing through the same circuit
(d) none of the above
Ans: b
The square waveform of current has following relation between r.m.s. value and average value.
(a) r.m.s. value is equal to average value
(b) r.m.s. value of current is greater than average value
(c) r.m.s. value of current is less than average value
(d) none of the above
Ans: a
The double energy transient occur in the
(a) purely inductive circuit
(b) R-L circuit
(c) R-C circuit
(d) R-L-C circuit
Ans: d
The transient currents are associated with the
(a) changes in the stored energy in the inductors and capacitors
(b) impedance of the circuit
(c) applied voltage to the circuit
(d) resistance of the circuit
Ans: a
The power factor at resonance in R-L- C parallel circuit is
(a) zero
(b) 0.08 lagging
(c) 0.8 leading
(d) unity
Ans: d
In the case of an unsymmetrical alternating current the average value must always be taken over
(a) unsymmetrical part of the wave form
(b) the quarter cycle
(c) the half cycle
(d) the whole cycle
Ans: d
In a pure resistive circuit
(a) current lags behind the voltage by 90°
(b) current leads the voltage by 90°
(c) current can lead or lag the voltage by 90°
(d) current is in phase with the voltage
Ans: d
In a pure inductive circuit
(a) the current is in phase with the voltage
(b) the current lags behind the voltage by 90°
(c) the current leads the voltage by 90°
(d) the current can lead or lag by 90°
Ans: b
In a circuit containing R, L and C, power loss can take place in
(a) C only
(b) L only
(c) R only
(d) all above
Ans: c
Inductance of coil
(a) is unaffected by the supply frequency
(b) decreases with the increase in supply frequency
(c) increases with the increase in supply frequency
(d) becomes zero with the increase in supply frequency
Ans: c
In any A.C. circuit always
(a) apparent power is more than actual power
(b) reactive power is more than apparent power
(c) actual power is more than reactive power
(d) reactive power is more than actual power
Ans: a
Which of the following circuit component opposes the change in the circuit voltage ?
(a) Inductance
(b) Capacitance
(c) Conductance
(d) Resistance
Ans:
In a purely inductive circuit
(a) actual power is zero
(b) reactive power is zero
(c) apparent power is zero
(d) none of above is zero
Ans: a
Power factor of electric bulb is
(a) zero
(b) lagging
(c) leading
(d) unity
Ans: d
Pure inductive circuit takes power from the A.C. line when
(a) applied voltage decreases but current increases
(b) applied voltage increases but current decreases
(c) both applied voltage and current increase
(d) both applied voltage and current decrease
Ans: a
Time constant of a circuit is the time in seconds taken after the application of voltage to each
(a) 25% of maximum value
(b) 50% of maximum value
(c) 63% of maximum value
(d) 90% of the maximum value
Ans: c
Time constant of an inductive circuit
(a) increases with increase of inductance and decrease of resistance
(b) increases with the increase of inductance and the increase of resistance
(c) increases with the decrease of inductance and decrease of resistance
(d) increases with decrease of inductance and increase of resistance
Ans: a
Time constant of a capacitive circuit
(a) increases with the decrease of capacitance and decrease of resistance
(b) increases with the decrease of capacitance and increase of resistance
(c) increases with the increase of capacitance and decrease of resistance
(d) increase with increase of capacitance and increase of resistance
Ans: d
Magnitude of current at resonance in R-L-C circuit
(a) depends upon the magnitude of R
(b) depends upon the magnitude of L
(c) depends upon the magnitude of C
(d) depends upon the magnitude of R, Land C
Ans: a

Circuit Theory

In a R-L-C circuit
(a) power is consumed in resistance and is equal to I R
(b) exchange of power takes place between inductor and supply line
(c) exchange of power takes place between capacitor and supply line
(d) exchange of power does not take place between resistance and the supply line
(e) all above are correct
Ans: e
In R-L-C series resonant circuit magnitude of resonance frequency can be changed by changing the value of
(a) R only
(b) L only
(c)C only
(d)LorC
(e) R,LorC
Ans: d
In a series L-C circuit at the resonant frequency the
(a) current is maximum
(b) current is minimum
(c) impedance is maximum
(d) voltage across C is minimum
Ans: a
The time constant of a series R-C circuit is given by
(a) R/C
(b) RC2
(c) RC
(d) R2C
Ans: c
If resistance is 20 Q. and inductance is 27 in a R-L series circuit, then time constant of this circuit will be
(a) 0.001 s
(b) 0.1 s
(c) 10 s
(d) 100 s
Ans: b
Which of the following coil will have large resonant frequency ?
(a) A coil with large resistance
(b) A coil with low resistance
(c) A coil with large distributed capacitance
(d) A coil with low distributed capacitance
Ans: c
If a sinusoidal wave has frequency of 50 Hz with 30 A r.m.s. current which of the following equation represents this wave ?
(a) 42.42 sin 3141
(b) 60 sin 25 t
(c) 30 sin 50 t
(d) 84.84 sin 25 t
Ans: a
The safest value of current the human body can carry for more than 3 second is
(a) 4 mA
(b) 9 mA
(c) 15 mA
(d) 25 mA
Ans: b
A pure inductance connected across 250 V, 50 Hz supply consumes 100 W.
This consumption can be attributed to
(a) the big size of the inductor
(b) the reactance of the inductor
(c) the current flowing in the inductor
(d) the statement given is false
Ans: d
The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA
The power drawn by the circuit is
(a) 12 kW
(b) 22 kW
(c) 32 kW
(d) 64 kW
Ans: c
The effective resistance of an iron-cored choke working on ordinary supply frequency is more than its true resistance because of
(a) iron loss in core
(b) skin effect
(c) increase in temperature
(d) capacitive effect between adjacent coil turns
Ans: a
In an AC. circuit, a low value of kVAR compared with kW indicates
(a) low efficiency
(b) high power factor
(c) unity power factor
(d) maximum load current
Ans: b
In AC. circuits, laminated iron is invariably used in order to
(a) reduce eddy current loss
(b) increase heat radiation
(c) make assembly cheap and easier
(d) reduce circuit permeability
Ans: a
The ratio of active power to apparent power is known as factor.
(a) demand
(b) load
(c) power
(d) form
Ans: c
All definitions of power factor of a series R-L-C circuit are correct except
(a) ratio of net reactance and impedance
(b) ratio of kW and kVA
(c) ratio of J and Z
(d) ratio of W and VA
Ans: a
The apparent power drawn by an A.C. circuit is 10 kVA and active power is 8 kW. The reactive power in the circuit is
(a) 4 kVAR
(b) 6 kVAR
(c) 8 kVAR
(d) 16 kVAR
Ans: b
What will be the phase angle between two alternating waves of equal frequency, when one wave attains maximum value the other is at zero value ?
(a) 0°
(b) 45°
(c) 90°
(d) 180°
Ans: c
The purpose of a parallel circuit resonance is to magnify
(a) current
(b) voltage
(c) power
(d) frequency
Ans: b
In an A.C. circuit power is dissipated in
(a) resistance only
(b) inductance only
(c) capacitance only
(d) none of the above
Ans: a
In a parallel R-C circuit, the current always______the applied voltage
(a) lags
(b) leads
(c) remains in phase with
(d) none of the above
Ans: b
At very low frequencies a series R-C circuit behaves as almost purely
(a) resistive
(b) inductive
(c) capacitive
(d) none of the above
Ans: c
Skin effect occurs when a conductor carries current at_____ frequencies.
(a) very low
(b) low
(c) medium
(d) high
Ans: d
At ______ frequencies the parallel R-L circuit behaves as purely resistive.
(a) low
(b) very low
(c) high
(d) very high
Ans: d
In a sine wave the slope is constant
(a) between 0° and 90°
(b) between 90° and 180°
(c) between 180° and 270°
(d) no where
Ans: d
The power is measured in terms of decibles in case of
(a) electronic equipment
(b) transformers
(c) current transformers
(d) auto transformers
Ans: a
Capacitive susceptance is a measure of
(a) reactive power in a circuit
(b) the extent of neutralisation of reactive power in a circuit
(c) a purely capacitive circuit’s ability to pass current
(d) a purely capacitive circuit’s ability to resist the flow of current
Ans: c
Which of the following statements pertains to resistors only ?
(a) can dissipate considerable amount of power
(6) can act as energy storage devices
(c) connecting them in parallel in¬creases the total value
(d) oppose sudden changes in voltage
Ans: a
Which of the following refers to a parallel circuit ?
(a) The current through each element is same
(b) The voltage across element is in proportion to it’s resistance value
(c) The equivalent resistance is greater than any one of the resistors
(d) The current through any one element is less than the source current
Ans: d
Aphasoris
(a) a line which represents the magnitude and phase of an alternating quantity
(b) a line representing the magnitude and direction of an alternating quantity
(c) a coloured tag or band for distinction between different phases of a 3-phase supply
(d) an instrument used for measuring phases of an unbalanced 3-phase load
Ans: a
A parallel AC. circuit in resonance will
(a) have a high voltage developed across each inductive and capacitive section
(b) have a high impedance
(c) act like a resistor of low value
(d) have current in each section equal to the line current
Ans: b
Wire-wound resistors are unsuitable for use at high frequencies because they
(a) create more electrical noise
(b) are likely to melt under excessive eddy current heat
(c) consume more power
(d) exhibit unwanted inductive and capacitive effects
Ans: d
The inductance of a coil can be increased by
(a) increasing core length
(b) decreasing the number of turns
(c) decreasing the diameter of the former
(d) choosing core material having high relative permeability
Ans: d
In a three-phase supply floating neutral is undesirable because it way give rise to
(a) high voltage across the load
(b) low voltage across the load
(c) unequal line voltages across the load
Ans: c
Which of the following waves has the highest value of peak factor ?
(a) Square wave
(b) Sine wave
(c) Half wave rectified sine wave
(d) Triangular wave
Ans: c
The frequency of domestic power supply in India is
(a) 200 Hz
(b) 100 Hz
(c) 60 Hz
(d) 50 Hz
Ans: d
The r.m.s. value of half wave rectified sine wave is 200 V. The r.m.s. value of full wave rectified AC. will be
(a) 282.8 V
(b) 141.4 V
(c) 111 V
(d) 100 V
Ans: a
The r.m.s. value of pure cosine function is
(a) 0.5 of peak value
(b) 0.707 of peak value
(c) same as peak value
(d) zero
Ans: b
Ohm is unit of all of the following except
(a) inductive reactance
(b) capacitive reactance
(c) resistance
(d) capacitance
Ans: d
The series and parallel resonance on L-C circuit’ differs in that
(a) series resistance needs a low-resistance source for sharp rise in current
(b) series resonance needs a high-resistance source for sharp increase in current
(c) parallel resonance needs a low-resistance source for a sharp in¬crease in impedance
(d) parallel resonance needs a low-resistance source for a sharp rise in line current
Ans: a
The phosphors for which of the following pair are 180° out of phase for VL, VC and VR?
(a) Vc and VR
(b) VL and VR
(c) Vc and VL
(d) none of the above
Ans: c
The frequency of an alternating current is
(a) the speed with which the alternator runs
(b) the number of cycles generated in one minute
(c) the number of waves passing through a point in one second
(d) the number of electrons passing through a point in one second
Ans: c
A pure capacitor connected across an A.C. voltage consumed 50 W. This is due to
(a) the capacitive reactance in ohms
(b) the current flowing in capacitor
(c) the size of the capacitor being quite big
(d) the statement is incorrect
Ans: d
The power factor of a D.C. circuit is always
(a) less than unity
(b) unity
(c) greater than unity
(d) zero
Ans: b
The product of apparent power and cosine of the phase angle between circuit voltage and current is
(a) true power
(b) reactive power
(c) volt-amperes
(d) instantaneous power
Ans: a
The equation of 50 Hz current sine wave having r.m.s. value of 60 A is
(a) 60 sin 25 t
(b) 60 sin 50 t
(c) 84.84 sin 3141
(d) 42.42 sin 314 t
Ans: c
An A.C. voltage is impressed across a pure resistance of 3.5 ohms in parallel with a pure inductance of impedance of 3.5 ohms,
(a) the current through the resistance is more
(b) the current through the resistance is less
(c) both resistance and inductance carry equal currents
(d) none of the above
Ans: c
In a pure inductive circuit if the supply frequency is reduced to 1/2, the current will
(a) be reduced by half
(b) be doubled
(c) be four times as high
(d) be reduced to one fourth
Ans: b
In a pure capacitive circuit if the supply frequency is reduced to 1/2, the current will
(a) be reduced by half
(b) be doubled
(c) be four times at high
(d) be reduced to one fourth
Ans: a
When an alternating current passes through an ohmic resistance the electrical power converted into heat is
(a) apparent power
(b) true power
(c) reactive power
(d) none of the above
Ans: b
In each of the three coils of a three phase generator, an alternating voltage having an r.m.s. value of 220 V is induced. Which of the following values is indicated by the voltmeters ?
(a) 220 V
(b) 220V3V
(c) 220/V3 V
(d) none of the above
Ans: a

D.C. GENERATORS

Lamination’s of core are generally made of
(a) case iron
(b) carbon
(c) silicon steel
(d) stainless steel
Ans: c
Which of the following could be lamina-proximately the thickness of lamination’s of a D.C. machine ?
(a) 0.005 mm
(b) 0.05 mm
(c) 0.5 m
(d) 5 m
Ans: c
The armature of D.C. generator is laminated to
(a) reduce the bulk
(b) provide the bulk
(c) insulate the core
(d) reduce eddy current loss
Ans:d
The resistance of armature winding depends on
(a) length of conductor
(b) cross-sectional area of the conductor
(c) number of conductors
(d) all of the above
Ans: d
The field coils of D.C. generator are usually made of
(a) mica
(b) copper
(c) cast iron
(d) carbon
Ans: b
The commutator segments are connected to the armature conductors by means of
(a) copper lugs
(b) resistance wires
(c) insulation pads
(d) brazing
Ans: a
In a commutator
(a) copper is harder than mica
(b) mica and copper are equally hard
(c) mica is harder than copper
(d) none of the above
Ans: c
In D.C. generators the pole shoes are fastened to the pole core by
(a) rivets
(b) counter sunk screws
(c) brazing
(d) welding
Ans: b
According to Fleming’s right-hand rule for finding the direction of induced e.m.f., when middle finger points in the direction of induced e.m.f., forefinger will point in the direction of
(a) motion of conductor
(b) lines of force
(c) either of the above
(d) none of the above
Ans: b
Fleming’s right-hand rule regarding direction of induced e.m.f., correlates
(a) magnetic flux, direction of current flow and resultant force
(b) magnetic flux, direction of motion and the direction of e.m.f. induced
(c) magnetic field strength, induced voltage and current
(d) magnetic flux, direction of force and direction of motion of conductor
Ans: b
While applying Fleming’s right-hand rule to And the direction of induced e.m.f., the thumb points towards
(a) direction of induced e.m.f.
(b) direction of flux
(c) direction of motion of the conductor if forefinger points in the direction of generated e.m.f.
(d) direction of motion of conductor, if forefinger points along the lines of flux
Ans: d
The bearings used to support the rotor shafts are generally
(a) ball bearings
(b) bush bearings
(c) magnetic bearmgs
(d) needle bearings
Ans: a
In D.C. generators, the cause of rapid brush wear may be
(a) severe sparking
(b) rough commutator surface
(c) imperfect contact
(d) any of the above
Ans: d
In lap winding, the number of brushes is always
(a) double the number of poles
(b) same as the number of poles
(c) half the number of poles
(d) two
Ans: b
For a D.C. generator when the number of poles and the number of armature conductors is fixed, then which winding will give the higher e.m.f. ?
(a) Lap winding
(b) Wave winding
(c) Either of (a) and (b) above
(d) Depends on other features of design
Ans: b
In a four-pole D.C. machine
(a) all the four poles are north poles
(b) alternate poles are north and south
(c) all the four poles are south poles
(d) two north poles follow two south poles
Ans: b
Copper brushes in D.C. machine are used
(a) where low voltage and high currents are involved
(b) where high voltage and small cur-rents are involved
(c) in both of the above cases
(d) in none of the above cases
Ans: a
A separately excited generator as compared to a self-excited generator
(a) is amenable to better voltage control
(b) is more stable
(c) has exciting current independent of load current
(d) has all above features
Ans: d
In case of D.C. machines, mechanical losses are primary function of
(a) current
(b) voltage
(c) speed
(d) none of above
Ans: c
Iron losses in a D.C. machine are independent of variations in
(a) speed
(b) load
(c) voltage
(d) speed and voltage
Ans: b
In D.C. generators, current to the external circuit from armature is given through
(a) commutator
(b) solid connection
(c) slip rings
(d) none of above
Ans: a
Brushes of D.C. machines are made of
(a) carbon
(b) soft copper
(c) hard copper
(d) all of above
Ans: a
If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by
(a)Blv
(b)Blv2
(c)Bl2v
(d)Bl2v2
Ans: a
In case of a 4-pole D.C. generator provided with a two layer lap winding with sixteen coils, the pole pitch will be
(a) 4
(b) 8
(c) 16
(d) 32
Ans: b
The material for commutator brushes is generally
(a) mica
(b) copper
(c) cast iron
(d) carbon
Ans: d
The insulating material used between the commutator segments is normally
(a) graphite
(b) paper
(c) mica
(d) insulating varnish
Ans: c
In D.C. generators, the brushes on commutator remain in contact with conductors which
(a) lie under south pole
(b) lie under north pole
(c) lie under interpolar region
(d) are farthest from the poles
Ans: c
If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be
(a) demagnetisation only
(b) cross magnetisation as well as mag¬netisation
(c) crossmagnetisation as well as demagnetising
(d) cross magnetisation only
Ans: c
Armature reaction of an unsaturated D.C. machine is
(a) crossmagnetising
(b) demagnetising
(c) magnetising
(d) none of above
Ans: a
D.C. generators are connected to the busbars or disconnected from them only under the floating condition
(a) to avoid sudden loading of the primemover
(b) to avoid mechanicaljerk to the shaft
(c) to avoid burning of switch contacts
(d) all above
Ans: d
Eddy currents are induced in the pole shoes of a D.C. machine due to
(a) oscillating magnetic field
(b) pulsating magnetic flux
(c) relative rotation between field and armature
(d) all above
Ans: c
In a D.C. machine, short-circuited field coil will result in
(a) odour of barning insulation
(b) unbalanced magnetic pull producing vibrations
(c) reduction of generated voltage for which excitation has to be increased to maintain the voltage
(d) all above
Ans:
Equilizer rings are required in case armature is
(a) wave wound
(b) lap wound
(c) delta wound
(d) duplex wound
Ans: b
Welding generator will have
(a) lap winding
(b) wave winding
(c) delta winding
(d) duplex wave winding
Ans: a
In case of D.C. machine winding, number of commutator segments is equal to
(a) number of armature coils
(b) number of armature coil sides
(c) number of armature conductors
(d) number of armature turns
Ans: a
For a D.C. machines laboratory following type of D.C. supply will be suitable
(a) rotary converter
(b) mercury are rectifier
(c) induction motor D.C. generator set
(d) synchronous motor D.C. generator set
Ans: c
The function of pole shoes in the case of D.C. machine is
(a) to reduce the reluctance of the mag¬netic path
(b) to spread out the flux to achieve uniform flux density
(c) to support the field coil
(d) to discharge all the above functions
Ans: d
In the case of lap winding resultant pitch is
(a) multiplication of front and back pitches
(b) division of front pitch by back pitch
(c) sum of front and back pitches
(d) difference of front and back pitches
Ans: d
A D.C. welding generator has
(a) lap winding
(b) wave moving
(c) duplex winding
(d) any of the above
Ans: a
Which of the following statement about D.C. generators is false ?
(a) Compensating winding in a D.C. machine helps in commutation
(b) In a D. C. generator interpoles winding is connected in series with the armature winding
(c) Back pitch and front pitch are both odd and approximately equal to the pole pitch
(d) Equilizing bus bars are used with parallel running of D.C. shunt gen¬erators
Ans: d
The demagnetising component of armature reaction in a D.C. generator
(a) reduces generator e.m.f.
(b) increases armature speed
(c) reduces interpoles flux density
(d) results in sparking trouble
Ans: a
Magnetic field in a D.C. generator is produced by
(a) electromagnets
(b) permanent magnets
(c) both (a) and (b)
(d) none of the above
Ans: a
The number of brushes in a commutator depends on
(a) speed of armature
(b) type of winding
(c) voltage
(d) amount of current to be collected
Ans: d
Compensating windings are used in D.C. generators
(a) mainly to reduce the eddy currents by providing local short-circuits
(b) to provide path for the circulation of cooling air
(c) to neutralise the cross-magnetising effect of the armature reaction
(d) none of the above
Ans: c
Which of the following components of a D.C, generator plays vital role for providing direct current of a D.C. generator ?
(a) Dummy coils
(b) Commutator
(c) Eye bolt
(d) Equilizer rings
Ans: b
In a D.C. generator the ripples in the direct e.m.f. generated are reduced by
(a) using conductor of annealed copper
(b) using commutator with large number of segments
(c) using carbon brushes of superior quality
(d) using equiliser rings
Ans: c
In D.C. generators, lap winding is used for
(a) high voltage, high current
(b) low voltage, high current
(c) high voltage, low current
(d) low voltage, low current
Ans: b
Two generators A and B have 6-poles each. Generator A has wave wound armature while generator B has lap wound armature. The ratio of the induced e.m.f. is generator A and B will be
(a) 2 : 3
(b) 3 : 1
(c) 3 : 2
(d) 1 : 3
Ans: b
The voltage drop for which of the following types of brush can be expected to be least ?
(a) Graphite brushes
(b) Carbon brushes
(c) Metal graphite brushes
(d) None of the above
Ans: c
The e.m.f. generated by a shunt wound D.C. generator isE. Now while pole flux remains constant, if the speed of the generator is doubled, the e.m.f. generated will be
(a) E/2
(b) 2E
(c) slightly less than E
(d) E
Ans: b
In a D.C. generator the actual flux distribution depends upon
(a) size of air gap
(b) shape of the pole shoe
(c) clearance between tips of the ad¬jacent pole shoes
(d) all of the above
Ans:
The armature core of a D.C. generator is usually made of
(a) silicon steel
(b) copper
(c) non-ferrous material
(d) cast-iron
Ans: a

9.63. Satisfactory commutation of D.C. machines requires
(a) brushes should be of proper grade and size
(b) brushes should smoothly run in the holders
(c) smooth, concentric commutator properly undercut
(d) all of the above
Ans: d

Open circuited armature coil of a D.C. machine is
(a) identified by the scarring of the commutator segment to which open circuited coil is connected
(b) indicated by a spark completely around the commutator
(c) both (a) and (b)
(d) none of the above
Ans: c
In a D.C. machine, fractional pitch winding is used
(a) to increase the generated voltage
(b) to reduce sparking
(c) to save the copper because of shorter end connections
(d) due to (b) and (c) above
Ans:
For the parallel operation of two or more D.C. compound generators, we should ensure that
(a) voltage of the incoming generator should be same as that of bus bar
(b) polarity of incoming generator should be same as that of bus bar
(c) all the series fields should be run in parallel by means of equilizer connection
(d) series fields of all generators should be either on positive side or negative side of the armature
(e) all conditions mentioned above should be satisfied
Ans: d
D.C. series generator is used
(a) to supply traction load
(b) to supply industrial load at constant voltage
(c) voltage at the toad end of the feeder
(d) for none of the above purpose
Ans: c
Following D.C. generator will be in a position to build up without any residual magnetism in the poles
(a) series generator
(b) shunt generator
(c) compound generator
(d) self-excited generator
Ans: d
Interpole flux should be sufficient to
(a) neutralise the commutating self induced e.m.f.
(b) neutralise the armature reaction flux
(c) neutralise both the armature reaction flux as well as commutating e.m.f. induced in the coil
(d) perform none of the above functions
Ans: c
D.C. generator generally preferred for charging automobile batteries is
(a) series generator
(b) shunt generator
(c) long shunt compound generator
(d) any of’the above
Ans: c
In a D.C. generator the number of mechanical degrees and electrical degrees will be the same when
(a) r.p.m. is more than 300
(b) r.p.m. is less than 300
(c) number of poles is 4
(d) number of poles is 2
Ans: d
Permeance is the reciprocal of
(a) flux density
(b) reluctance
(c) ampere-turns
(d) resistance
Ans: b
In D.C. generators the polarity of the interpoles
(a) is the same as that of the main pole ahead
(b) is the same as that of the immediately preceding pole
(c) is opposite to that of the main pole ahead
(d) is neutral as these poles do not play part in generating e.m.f.
Ans: a
The e.m.f. generated in a D.C. generator is directly proportional to
(a) flux/pole
(b) speed of armature
(c) number of poles
(d) all of the above
Ans: b
In a D.C. generator the magnetic neutral axis coincides with the geometrical neutral axis, when
(a) there is no load on|he generator
(b) the generator runs on full load
(c) the generator runs on overload
(d) the generator runs on designed speed
Ans: a
In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralised by all of the following except
(a) interpoles
(b) dummy coils
(c) compensating winding
(d) shifting of axis of brushes
Ans: b
In D.C. generators on no-load, the air gap flux distribution in space is
(a) sinusoidal
(b) triangular
(c) pulsating
(d) flat topped
Ans: d
A shunt generator running at 1000 r.p.m. has generated e.m.f. as 200 V. If the speed increases to 1200 r.p.m., the generated e.m.f. will be nearly
(a) 150 V
(b) 175 V
(c) 240 V
(d) 290 V
Ans: c
The purpose of providing dummy coils in a generator is
(a) to reduce eddy current losses
(b) to enhance flux density
(c) to amplify voltage
(d) to provide mechanical balance for the rotor
Ans: d
In a shunt generator the voltage build up is generally restricted by
(a) speed limitation
(b) armature heating
(c) insulation restrictions
(d) saturation of iron
Ans:
If a D.C. generator fails to build up the probable cause could not be
(a) imperfect brush contact
(b) field resistance less than the critical resistance
(c) no residual magnetism in the generator
(d) faulty shunt connections tending to reduce the residual magnetism
Ans: b
Flashing the field of D.C. generator means
(a) neutralising residual magnetism
(b) creating residual magnetism by a D.C. source
(c) making the magnetic losses of forces parallel
(d) increasing flux density by adding extra turns of windings on poles
Ans: b
The e.m.f. induced in the armature of a shunt generator is 600 V. The armature resistance is 0.1 ohm. If the armature current is 200 A, the terminal voltage will be
(a) 640 V
(b) 620 V
(c) 600 V
(d) 580 V
Ans: d
In a D.C. generator the critical resistance refers to the resistance of
(a) brushes
(b) field
(c) armature
(d) load
Ans: b
To achieve sparkless commutation brushes of a D.C. generator are rockedm ahead so as to bring them
(a) just ahead of magnetic neutral axis
(b) in magnetic neutral axis
(c) just behind the magnetic neutral axis
Ans: a
Armature coil is short circuited by brushes when it lies
(a) along neutral axis
(b) along field axis
(c) in any of the above positions
(d) in none of the above positions
Ans: a
A cumulatively compounded long shunt generator when operating as a motor would be
(a) cumulatively compounded long shunt
(b) differentially compounded long shunt
(c) cumulatively compounded short shunt
(d) differentially compounded short shunt
Ans: b
To avoid formation of grooves in the commutator of a D.C. machine
(a) the brushes of opposite polarity should track each other
(b) the brushes of same polarity should track each other
(c) brush position has no effect on the commutator grooving
Ans: a
The following constitute short-circuit in the armature winding.
(a) Insulation failure between two commutator bars
(6) Insulation failure between two turns of a coil
(c) Two of more turns of the same coil getting grounded
(d) All of the above
Ans: d
The rapid wear of brushes takes place due to
(a) abrasion from dust
(b) excessive spring pressure
(c) rough commutator bars
(d) high mica insulation between com-mutation bars
(e) all of the above factors
Ans: e
Number of tappings for each equilizer ring is equal to
(a) number of pole pairs
(b) number of poles
(c) number of parallel paths
(d) number of commutator segments
Ans: a
A D.C. generator can be considered as
(a) rectifier
(b) primemover
(c) rotating amplifier
(d) power pump
Ans: c
In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called
(a) rotor
(b) stator
(c) field
(d) armature
Ans: d
In a D.C. machine stray loss is the sum of
(a) total copper loss and mechanical loss
(b) armature copper loss and iron loss
(c) shunt field copper loss and mechanical loss
(d) iron loss and mechanical loss
Ans: d
Lap winding is composed of
(a) any even number of conductors
(b) any odd number of conductors
(c) that even number which is exact multiple of poles + 2
(d) that even number which is exact multiple of poles
Ans: a
In a D.C. generator in case the resistance of the field winding is increased, then output voltage will
(a) increase
(b) decrease
(c) remain unaffected
(d) fluctuate heavily
Ans: b
An exciter for a turbo generator is a
(a) separately excited generator
(b) shunt generator
(c) series generator
(d) compound generator
Ans: b
In case of a flat compounded generator
(a) voltage generated is less than the rated voltage
(b) generated voltage is proportional to the load on the generator
(c) voltage remains constant irrespective of the load
(d) speed varies in proportion to the load on the generator
Ans: c
Which of the following generator will have negligible terminal voltage while running on no-load ?
(a) Series generator
(b) Shunt generator
(c) Compound generator
(d) Separately excited generator
Ans: a
Which of the following D.C. generators will be in a position to build up without any residual magnetism in the poles ?
(a) Series generator
(b) Shunt generator
(c) Compound generator
(d) None of the above
Ans: d
In over compounded generator, full load terminal voltage is
(a) almost zero
(b) less than no load terminal voltage
(c) more than no load terminal voltage
(d) equal to no-load terminal voltage
Ans: c
In a level compounded D.C. generator, full load terminal voltage is
(a) negligibly low
(b) equal to no-load terminal voltage
(c) more than no-load terminal voltage
(d) less than no-load terminal voltage
Ans: b
The terminal voltage of a D.C. shunt generator drops on load because of all of the following reasons except
(a) armature reaction
(b) armature resistance drop
(c) field weakening due to armature reaction and armature
(d) commutation
Ans: d
In a D.C. generator
(a) external resistance = internal char-acteristic – armature reaction
(b) internal characteristic = magnetisation characteristic – ohmic drop
(c) external characteristic = magnetisation characteristic – ohmic drop – armature reaction
(d) magnetisation characteristic = external characteristic
Ans: c
A sinusoidal voltage of 5 Hz is applied to the field of a shunt generator. The armature voltage wave
(a) will be zero
(b) will be of 5 Hz
(c) will be of 5 xiVHz
(d) will be of v Hz 5
Ans: b
A 220 V D.C. generator is run at full speed without any excitation. The open circuit voltage will be
(a) zero
(b) about 2 V
(c) about 50 V
(d) 220 V
Ans: b
In a separately excited generator supplying rated load the armature reaction ,
(a) is always present
(b) is always absent
(c) may be sometimes present
(d) none of the above
Ans: a
If residual magnetism is present in a D.C. generator, the induced e.m.f. at zero speed will be
(a) zero
(b) small
(c) the same as rated voltage
(d) high
Ans: a
Armature reaction in a generator results in
(a) demagnetization of leading pole tip and magnetization of trailing pole tip
(b) demagnetization of trailing pole tip and magnetization of leading pole tip
(c) demagnetizing the center of all poles
(d) magnetizing the center of all poles
Ans: a
Following energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure.
(a) Series field
(b) Compensating field
(c) Inter pole field
(d) Shunt field
Ans:
Wave winding is composed of
(a) any even number of conductors
(b) any odd number of conductors
(c) that even number which is exact multiple of poles + 2
(d) that even number which is exact multiple of poles
Ans: c
The critical resistance of the D.C. generator is the resistance of
(a) field
(b) brushes
(c) armature
(d) load
Ans: a
When two D.C. series generators are running in parallel, an equalizer bar is used
(a) to increase the speed and hence generated e.m.f.
(b) to increase the series flux
(c) so that two similar machines will pass approximately equal currents to the load
(d) to reduce the combined effect of ar-mature reaction of both machines
Ans: c
Which of the following generating machine will offer constant voltage on all loads ?
(a) Self-excited generator
(b) Separately excited generator
(c) Level compounded generator .
(d) All of the above
Ans: c
Which of the following generators will be preferred if they are required to be run in parallel ?
(a) Shunt generators
(b) Series generators
(c) Compound generators
(d) None of the above
Ans: a
Two generators are running in parallel. One of the generators may run as motor for which of the following reasons ?
(a) The direction of that generator is reversed
(b) The speed of that generator is increased
(c) The field of that generator is weakened
(d) That generator takes large share of loads
Ans: d
A D.C. generator works on the principle of
(a) Lenz’s law
(b) Ohm’s law
(c) Faraday’s law of electromagnetic induction
(d) none of the above
Ans: c
A series generator can self-excite
(a) only if the load current is zero
(b) only if the load current is not zero
(c) irrespective of the value of load current
(d) none of the above
Ans: b
A shunt generator can self-excite
(a) only if the resistance of the field circuit is less than critical value
(b) only if the resistance of the field circuit is greater than critical value
(c) irrespective of the value of the resistance in the field circuit
Ans: a
The terminal voltage of a series generator is 150 V when the load current is 5 A. If the load current is increased to 10 A, the terminal voltage will be
(a) 150 V
(b) less than 150 V
(c) greater than 150 V
(d) none of the above
Ans: c
The open circuit voltage of a compound generator is 250 V. At full load the terminal voltage
(a) will be less than 250 V
(b) will always be 250 V
(c) may be greater or less than 250 V
(d) none of the above
Ans: c
Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be
(a) 270 V
(b) 267.5 V
(c) 265 V
(d) 257.4 V
Ans: b
The essential condition for parallel operation of two D.C. generators is that they have ‘
(a) same kW rating
(b) the same operation r.p.m.
(c) the same drooping voltage characteristics
(d) same percentage regulation
Ans: c
When two D.C. generators are running in parallel an equalizer bar is used
(a) to increase the series flux
(b) to increase the generated e.m.f.
(c) to reduce the combined effect of AR-mature reaction of both the machines
(d) so that the two identical machines will pass approximately equal cur¬rents to the load
Ans: d
With a D.C. generator which of the following regulation is preferred ?
(a) 100% regulation
(b) infinite regulation
(c) 50% regulation
(d) 1% regulation
Ans: d
Which generator would you prefer for feeding long D.C. transmission lines ?
(a) Series generator
(b) Shunt generator
(c) Over compound generator
(d) Flat compound generator
Ans: c
In a D.C. generator the critical resistance can be increased by
(a) increasing its field resistance
(b) decreasing its field resistance
(c) increasing its speed
(d) decreasing its speed
Ans: c
The number of armature parallel paths in a two-pole D.C. generator having duplex lap winding is
(a) 2
(b) 4
(c) 6
(d) 8
Ans: b
For both lap and wave winding’s, there are as many commutator bars as the number of
(a) slots
(b) armature conductors
(c) winding elements
(d) poles
Ans: c
The series field of a short-shunt D.C. generator is excited by
(a) external current
(b) armature current
(c) shunt current
(d) load current
Ans: d
As a result of armature reaction, the reduction in the total mutual air gap flux in a D.C. generator is approximately
(a) 40 percent
(b) 25 percent
(c) 10 percent
(d) 5 percent
Ans: d
Shunt generators are most suited for stable parallel operation because of their
(a) rising voltage characteristics
(b) identical voltage characteristics
(c) drooping voltage characteristics
(d) linear voltage characteristics
Ans: c
The main factor which leads to unstable parallel operation of flat and over compounded generators is
(a) their rising voltage characteristics
(b) unequal number of turns in their series field winding’s
(c) unequal speed regulation of their prime movers
(d) unequal series field resistances
Ans: a
If a self excited D.C. generator after being installed, fails to build up on its first trial run, the first thing to do is to
(a) reverse the field connections
(b) increase the field resistance
(c) increase the speed of prime mover
(d) check armature insulation resistance
Ans: a

D.C. MOTORS

No-load speed of which of the following motor will be highest ?
(a) Shunt motor
(b) Series motor
(c) Cumulative compound motor
(d) Differentiate compound motor
Ans: b
The direction of rotation of a D.C. series motor can be changed by
(a) interchanging supply terminals
(b) interchanging field terminals
(c) either of (a) and (b) above
(d) None of the above
Ans: b
Which of the following application requires high starting torque ?
(a) Lathe machine
(b) Centrifugal pump
(c) Locomotive
(d) Air blower
Ans: c
If a D.C. motor is to be selected for conveyors, which rriotor would be preferred ?
(a) Series motor
(b) Shunt motor
(c) Differentially compound motor
(d) Cumulative compound motor
Ans: a
Which D.C. motor will be preferred for machine tools ?
(a) Series motor
(b) Shunt motor
(c) Cumulative compound motor
(d) Differential compound motor
Ans: b
Differentially compound D.C. motors can find applications requiring
(a) high starting torque
(b) low starting torque
(c) variable speed
(d) frequent on-off cycles
Ans: b
Which D.C. motor is preferred for elevators ?
(a) Shunt motor
(b) Series motor
(c) Differential compound motor
(d) Cumulative compound motor
Ans: d
According to Fleming’s left-hand rule, when the forefinger points in the direction of the field or flux, the middle finger will point in the direction of
(a) current in the conductor aovtaat of conductor
(c) resultant force on conductor
(d) none of the above
Ans: a
If the field of a D.C. shunt motor gets opened while motor is running
(a) the speed of motor will be reduced %
(b) the armature current will reduce
(c) the motor will attain dangerously high speed 1
(d) the motor will continue to nuvat constant speed
Ans: c
Starters are used with D.C. motors because
(a) these motors have high starting torque
(b) these motors are not self-starting
(c) back e.m.f. of these motors is zero initially
(d) to restrict armature current as there is no back e.m.f. while starting
Ans: d

Transformers

Which of the following does not change in a transformer ?
(a) Current
(b) Voltage
(c) Frequency
(d) All of the above
Ans: c
In a transformer the energy is conveyed from primary to secondary
(a) through cooling coil
(b) through air
(c) by the flux
(d) none of the above
Ans: c
A transformer core is laminated to
(a) reduce hysteresis loss
(b) reduce eddy current losses
(c) reduce copper losses
(d) reduce all above losses
Ans: b
The degree of mechanical vibrations produced by the laminations of a transformer depends on
(a) tightness of clamping
(b) gauge of laminations
(c) size of laminations
(d) all of the above
Ans: d
The no-load current drawn by transformer is usually what per cent of the full-load current ?
(a) 0.2 to 0.5 per cent
(b) 2 to 5 per cent
(c) 12 to 15 per cent
(d) 20 to 30 per cent
Ans: b
The path of a magnetic flux in a transformer should have
(a) high resistance
(b) high reluctance
(c) low resistance
(d) low reluctance
Ans: d
No-load on a transformer is carried out to determine
(a) copper loss
(b) magnetising current
(c) magnetising current and loss
(d) efficiency of the transformer
Ans: c
The dielectric strength of transformer oil is expected to be
(a) lkV
(b) 33 kV
(c) 100 kV
(d) 330 kV
Ans: b
Sumpner’s test is conducted on trans-formers to determine
(a) temperature
(b) stray losses
(c) all-day efficiency
(d) none of the above
Ans: a
The permissible flux density in case of cold rolled grain oriented steel is around
(a) 1.7 Wb/m2
(b) 2.7 Wb/m2
(c) 3.7 Wb/m2
(d) 4.7 Wb/m2
Ans: a
The efficiency of a transformer will be maximum when
(a) copper losses = hysteresis losses
(b) hysteresis losses = eddy current losses
(c) eddy current losses = copper losses
(d) copper losses = iron losses
Ans: d
No-load current in a transformer
(a) lags behind the voltage by about 75°
(b) leads the voltage by about 75°
(c) lags behind the voltage by about 15°
(d) leads the voltage by about 15°
Ans: a
The purpose of providing an iron core in a transformer is to
(a) provide support to windings
(b) reduce hysteresis loss
(c) decrease the reluctance of the magnetic path
(d) reduce eddy current losses
Ans: c
Which of the following is not a part of transformer installation ?
(a) Conservator
(b) Breather
(c) Buchholz relay
(d) Exciter
Ans: d
While conducting short-circuit test on a transformer the following side is short circuited
(a) High voltage side
(b) Low voltage side
(c) Primary side
(d) Secondary side
Ans: b
In the transformer following winding has got more cross-sectional area
(a) Low voltage winding
(b) High voltage winding
(c) Primary winding
(d) Secondary winding
Ans: a
A transformer transforms
(a) voltage
(b) current
(c) power
(d) frequency
Ans: c
A transformer cannot raise or lower the voltage of a D.C. supply because
(a) there is no need to change the D.C. voltage
(b) a D.C. circuit has more losses
(c) Faraday’s laws of electromagnetic induction are not valid since the rate of change of flux is zero
(d) none of the above
Ans: c
Primary winding of a transformer
(a) is always a low voltage winding
(b) is always a high voltage winding
(c) could either be a low voltage or high voltage winding
(d) none of the above
Ans: c
Which winding in a transformer has more number of turns ?
(a) Low voltage winding
(b) High voltage winding
(c) Primary winding
(d) Secondary winding
Ans: b
Efficiency of a power transformer is of the order of
(a) 100 per cent
(b) 98 per cent
(c) 50 per cent
(d) 25 per cent
Ans: b
In a given transformer for given applied voltage, losses which remain constant irrespective of load changes are
(a) friction and windage losses
(b) copper losses
(c) hysteresis and eddy current losses
(d) none of the above
Ans: c
A common method of cooling a power transformer is
(a) natural air cooling
(b) air blast cooling
(c) oil cooling
(d) any of the above
Ans: c
The no load current in a transformer lags behind the applied voltage by an angle of about
(a) 180°
(b) 120″
(c) 90°
(d) 75°
Ans: d
In a transformer routine efficiency depends upon
(a) supply frequency
(b) load current
(c) power factor of load
(d) both (b) and (c)
Ans: d
In the transformer the function of a conservator is to
(a) provide fresh air for cooling the transformer
(b) supply cooling oil to transformer in time of need
(c) protect the transformer from damage when oil expends due to heating
(d) none of the above
Ans: c
Natural oil cooling is used for transformers up to a rating of
(a) 3000 kVA
(b) 1000 kVA
(c) 500 kVA
(d) 250 kVA
Ans: a
Power transformers are designed to have maximum efficiency at
(a) nearly full load
(b) 70% full load
(c) 50% full load
(d) no load
Ans: a
The maximum efficiency of a distribution transformer is
(a) at no load
(b) at 50% full load
(c) at 80% full load
(d) at full load
Ans: b
Transformer breaths in when
(a) load on it increases
(b) load on it decreases
(c) load remains constant
(d) none of the above
Ans: b
No-load current of a transformer has
(a) has high magnitude and low power factor
(b) has high magnitude and high power factor
(c) has small magnitude and high power factor
(d) has small magnitude and low power factor
Ans: d
Spacers are provided between adjacent coils
(a) to provide free passage to the cooling oil
(b) to insulate the coils from each other
(c) both (a) and (b)
(d) none of the above
Ans: a
Greater the secondary leakage flux
(a) less will be the secondary induced e.m.f.
(b) less will be the primary induced e.m.f.
(c) less will be the primary terminal voltage
(d) none of the above
Ans: a
The purpose of providing iron core in a step-up transformer is
(a) to provide coupling between primary and secondary
(b) to increase the magnitude of mutual flux
(c) to decrease the magnitude of mag-netizing current
(d) to provide all above features
Ans: c
The power transformer is a constant
(a) voltage device
(b) current device
(c) power device
(d) main flux device
Ans: d
Two transformers operating in parallel will share the load depending upon their
(a) leakage reactance
(b) per unit impedance
(c) efficiencies
(d) ratings
Ans: b
If R2 is the resistance of secondary winding of the transformer and K is the transformation ratio then the equivalent secondary resistance referred to primary will be
(a) R2/VK
(b) R2IK2
(c) R22!K2
(d) R22/K
Ans: b
What will happen if the transformers working in parallel are not connected with regard to polarity ?
(a) The power factor of the two trans-formers will be different from the power factor of common load
(b) Incorrect polarity will result in dead short circuit
(c) The transformers will not share load in proportion to their kVA ratings
(d) none of the above
Ans: b
If the percentage impedances of the two transformers working in parallel are different, then
(a) transformers will be overheated
(b) power factors of both the transformers will be same
(c) parallel operation will be not possible
(d) parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load
Ans: d
In a transformer the tappings are generally provided on
(a) primary side
(b) secondary side
(c) low voltage side
(d) high voltage side
Ans: c
The use of higher flux density in the transformer design
(a) reduces weight per kVA
(6) reduces iron losses
(c) reduces copper losses
(d) increases part load efficiency
Ans: a
The chemical used in breather for transformer should have the quality of
(a) ionizing air
(b) absorbing moisture
(c) cleansing the transformer oil
(d) cooling the transformer oil.
Ans: b
The chemical used in breather is
(a) asbestos fiber
(b) silica sand
(c) sodium chloride
(d) silica gel
Ans: d
An ideal transformer has infinite values of primary and secondary inductances. The statement is
(a) true
(b) false
Ans: b
The transformer ratings are usually expressed in terms of
(a) volts
(b) amperes
(c) kW
(d) kVA
Ans: d
The noise resulting from vibrations of laminations set by magnetic forces, is termed as
(a) magnetostrication
(b) boo
(c) hum
(d) zoom
Ans: c
Hysteresis loss in a transformer varies as CBmax = maximum flux density)
(a) Bmax
(b) Bmax1-6
(C) Bmax1-83
(d) B max
Ans: b
Material used for construction of transformer core is usually
(a) wood
(b) copper
(c) aluminium
(d) silicon steel
Ans: d
The thickness of laminations used in a transformer is usually
(a) 0.4 mm to 0.5 mm
(b) 4 mm to 5 mm
(c) 14 mm to 15 mm
(d) 25 mm to 40 mm
Ans: a
The function of conservator in a transformer is
(a) to project against’internal fault
(b) to reduce copper as well as core losses
(c) to cool the transformer oil
(d) to take care of the expansion and contraction of transformer oil due to variation of temperature of sur-roundings
Ans: d
The highest voltage for transmitting electrical power in India is
(a) 33 kV.
(6) 66 kV
(c) 132 kV
(d) 400 kV
Ans: d
In a transformer the resistance between its primary and secondary is
(a) zero
(b) 1 ohm
(c) 1000 ohms
(d) infinite
Ans: d
A transformer oil must be free from
(a) sludge
(b) odour
(c) gases
(d) moisture
Ans: d
A Buchholz relay can be installed on
(a) auto-transformers
(b) air-cooled transformers
(c) welding transformers
(d) oil cooled transformers
Ans: d
Gas is usually not liberated due to dissociation of transformer oil unless the oil temperature exceeds
(a) 50°C
(b) 80°C
(c) 100°C
(d) 150°C
Ans: d
The main reason for generation of harmonics in a transformer could be
(a) fluctuating load
(b) poor insulation
(c) mechanical vibrations
(d) saturation of core
Ans: d
Distribution transformers are generally designed for maximum efficiency around
(a) 90% load
(b) zero load
(c) 25% load
(d) 50% load
Ans: d
Which of the following property is not necessarily desirable in the material for transformer core ?
(a) Mechanical strength
(6) Low hysteresis loss
(c) High thermal conductivity
(d) High permeability
Ans: c
Star/star transformers work satisfactorily when
(a) load is unbalanced only
(b) load is balanced only
(c) on balanced as well as unbalanced loads
(d) none of the above
Ans: b
Delta/star transformer works satisfactorily when
(a) load is balanced only
(b) load is unbalanced only
(c) on balanced as well as unbalanced loads
(d) none of the above
Ans: c
Buchholz’s relay gives warning and protection against
(a) electrical fault inside the transformer itself
(b) electrical fault outside the transformer in outgoing feeder
(c) for both outside and inside faults
(d) none of the above
Ans: a
The magnetising current of a transformer is usually small because it has
(a) small air gap
(b) large leakage flux
(c) laminated silicon steel core
(d) fewer rotating parts
Ans: a
Which of the following does not change in an ordinary transformer ?
(a) Frequency
(b) Voltage
(c) Current
(d) Any of the above
Ans: a
Which of the following properties is not necessarily desirable for the material for transformer core ?
(a) Low hysteresis loss
(b) High permeability
(c) High thermal conductivity
(d) Adequate mechanical strength
Ans: c
The leakage flux in a transformer depends upon
(a) load current
(b) load current and voltage
(c) load current, voltage and frequency
(d) load current, voltage, frequency and power factor
Ans: a
The path of the magnetic flux in transformer should have
(a) high reluctance
(b) low reactance
(c) high resistance
(d) low resistance
Ans: b
Noise level test in a transformer is a
(a) special test
(b) routine test
(c) type test
(d) none of the above
Ans: c
Which of the following is not a routine test on transformers ?
(a) Core insulation voltage test
(b) Impedance test
(c) Radio interference test
(d) Polarity test
Ans: c
A transformer can have zero voltage regulation at
(a) leading power factor
(b) lagging power factor
(c) unity power factor
(d) zero power factor
Ans: a
Helical coils can be used on
(a) low voltage side of high kVA transformers
(b) high frequency transformers
(c) high voltage side of small capacity transformers
(d) high voltage side of high kVA rating transformers
Ans: a
Harmonics in transformer result in
(a) increased core losses
(b) increased I2R losses
(c) magnetic interference with communication circuits
(d) all of the above
Ans: d
The core used in high frequency transformer is usually
(a) copper core
(b) cost iron core
(c) air core
(d) mild steel core
Ans: c
The full-load copper loss of a trans¬former is 1600 W. At half-load, the copper loss will be
(a) 6400 W
(b) 1600 W
(c) 800 W
(d) 400 W
Ans: d

1.74. The value of flux involved m the e.m.f. equation of a transformer is
(a) average value
(b) r.m.s. value
(c) maximum value
(d) instantaneous value
Ans: c

L.75. Silicon steel used in laminations mainly reduces
(a) hysteresis loss
(b) eddy current losses
(c) copper losses
(d) all of the above
Ans: a

Which winding of the transformer has less cross-sectional area ?
(a) Primary winding
(b) Secondary winding
(c) Low voltage winding
(d) High voltage winding
Ans: d
Power transformers are generally designed to have maximum efficiency around
(a) no-load
(b) half-load
(c) near full-load
(d) 10% overload
Ans: c

.78. Which of the following is the main advantage of an auto-transformer over a two winding transformer ?
(a) Hysteresis losses are reduced
(b) Saving in winding material
(c) Copper losses are negligible
(d) Eddy losses are totally eliminated
Ans: b

During short circuit test iron losses are negligible because
(a) the current on secondary side is negligible
(b) the voltage on secondary side does not vary
(c) the voltage applied on primary side is low
(d) full-load current is not supplied to the transformer
Ans: c
Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in
(a) short-circuiting of the secondaries
(b) power factor of one of the transformers is leading while that of the other lagging
(c) transformers having higher copper losses will have negligible core losses
(d) loading of the transformers not in proportion to their kVA ratings
Ans: d
The changes in volume of transformer cooling oil due to variation of atmospheric temperature during day and
night is taken care of by which part of transformer
(a) Conservator
(b) Breather
(c) Bushings
(d) Buchholz relay
Ans: a
An ideal transformer is one which has
(a) no losses and magnetic leakage
(b) interleaved primary and secondary windings
(c) a common core for its primary and secondary windings
(d) core of stainless steel and winding of pure copper metal
(e) none of the above
Ans: a
When a given transformer is run at its rated voltage but reduced frequency, its
(a) flux density remains unaffected
(b) iron losses are reduced
(c) core flux density is reduced
(d) core flux density is increased
Ans: d
In an actual transformer the iron loss remains practically constant from noload to fullload because
(a) value of transformation ratio remains constant
(b) permeability of transformer core remains constant
(c) core flux remains practically constant
(d) primary voltage remains constant
(c) secondary voltage remains constant
Ans: c
An ideal transformer will have maximum efficiency at a load such that
(a) copper loss = iron loss
(b) copper loss < iron loss
(c) copper loss > iron loss
(d) none of the above
Ans: a
If the supply frequency to the transformer is increased,”the iron loss will
(a) not change
(b) decrease
(c) increase
(d) any of the above
Ans: c
Negative voltage regulation is indicative that the load is
(a) capacitive only
(b) inductive only
(c) inductive or resistive
(d) none of the above
Ans: a
Iron loss of a transformer can be measured by
(a) low power factor wattmeter
(b) unity power factor wattmeter
(c) frequency meter
(d) any type of wattmeter
Ans: a
When secondary of a current transformer is open-circuited its iron core will be
(a) hot because of heavy iron losses taking place in it due to high flux density
(b) hot because primary will carry heavy current
(c) cool as there is no secondary current
(d) none of above will happen
Ans: a
The transformer laminations are insulated from each other by
(a) mica strip
(6) thin coat of varnish
(c) paper
(d) any of the above
Ans: b
Which type of winding is used in 3phase shell-type transformer ?
(a) Circular type
(b) Sandwich type
(c) Cylindrical type
(d) Rectangular type
Ans: b
During open circuit test of a transformer
(a) primary is supplied rated voltage
(b) primary is supplied full-load current
(c) primary is supplied current at reduced voltage
(d) primary is supplied rated kVA
Ans: a
Open circuit test on transformers is conducted to determine
(a) hysteresis losses
(b) copper losses
(c) core losses
(d) eddy current losses
Ans: c
Short circuit test on transformers is conducted to determine
(a) hysteresis losses
(b) copper losses
(c) core losses
(d) eddy current losses
Ans: b
For the parallel operation of single phase transformers it is necessary that they should have
(a) same efficiency
(b) same polarity
(c) same kVA rating
(d) same number of turns on the secondary side.
Ans: b
The transformer oil should have _____ volatility and _____ viscosity.
(a) low,low
(b) high,high
(c) low,high
(d) high,low
Ans: a
The function of breather in a transformer is
(a) to provide oxygen inside the tank
(b) to cool the coils during reduced load
(c) to cool the transformer oil
(d) to arrest flow of moisture when outside air enters the transformer
Ans: d
The secondary winding of which of the following transformers is always kept closed ?
(a) Step-up transformer
(b) Step-down transformer
(c) Potential transformer
(d) Current transformer
Ans: d
The size of a transformer core will depend on
(a) frequency
(b) area of the core
(c) flux density of the core material
(d) (a) and (b) both
Ans: d
N atural air coo ling is generally restricted for transformers up to
(a) 1.5 MVA
(b) 5 MVA
(c) 15 MVA
(d) 50 MVA
Ans: a
A shell-type transformer has
(a) high eddy current losses
(b) reduced magnetic leakage
(c) negligibly hysteresis losses
(d) none of the above
Ans: b
A transformer can have regulation closer to zero
(a) on full-load
(b) on overload
(c) on leading power factor
(d) on zero power factor
Ans: c
A transformer transforms
(a) voltage
(b) current
(c) current and voltage
(d) power
Ans: d
Which of the following is not the standard voltage for power supply in India ?
(a) llkV
(b) 33kV
(c) 66 kV
(d) 122 kV
Ans: d
Reduction in core losses and increase in permeability are obtained with transformer employing
(a) core built-up of laminations of cold rolled grain oriented steel
(b) core built-up of laminations of hot rolled sheet
(c) either of the above
(d) none of the above
Ans: a
In a power or distribution transformer about 10 per cent end turns are heavily insulated
(a) to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns
(b) to absorb the line surge voltage and save the winding of transformer from damage
(c) to reflect the line surge and save the winding of a transformer from damage
(d) none of the above
Ans: a
For given applied voltage, with the increase in frequency of the applied voltage
(a) eddy current loss will decrease
(b) eddy current loss will increase
(c) eddy current loss will remain unchanged
(d) none of the above
Ans: c
Losses which occur in rotating electric machines and do not occur in trans formers are
(a) friction and windage losses
(b) magnetic losses
(c) hysteresis and eddy current losses
(d) copper losses
Ans: a
In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are
(a) hysteresis and eddy current losses
(b) friction and windage losses
(c) copper losses
(d) none of the above
Ans: a
Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and
drawing a current of 10 A from 200 V A.C. supply is incorrect ?
(a) Its secondary current is 5 A
(b) Its secondary voltage is 400 V
(c) Its rating is 2 kVA
(d) Its secondary current is 20 A
(e) It is a step-up transformer
Ans: d
The secondary of a current transformer is always short-circuited under operating conditions because it
(a) avoids core saturation and high voltage induction
(b) is safe to human beings
(c) protects the primary circuit
(d) none of the above
Ans: a
In a transformer the resistance between its primary and secondary should be
(a) zero
(b) 10 Q
(c) 1000 Q
(d) infinity
Ans: d
A good voltage regulation of a transformer means
(a) output voltage fluctuation from no load to full load is least
(b) output voltage fluctuation with power factor is least
(c) difference between primary and secondary voltage is least
(d) difference between primary and secondary voltage is maximum
Ans: a
For a transformer, operating at constant load current, maximum efficiency will occur at
(a) 0.8 leading power factor
(b) 0.8 lagging power factor
(c) zero power factor
(d) unity power factor
Ans: d
Which of the following protection is normally not provided on small distribution transformers ?
(a) Overfluxing protection
(b) Buchholz relay
(c) Overcurrent protection
(d) All of the above
Ans: b
Which of the following acts as a protection against high voltage surges due to lightning and switching ?
(a) Horn gaps
(b) Thermal overload relays
(c) Breather
(d) Conservator
Ans: a
The efficiency of two identical transformers under load conditions can be determined by
(a) short-circuit test
(b) back-to-back test
(c) open circuit test
(d) any of the above
Ans: b
Which of the following insulating materials can withstand the highest temperature safely ?
(a) Cellulose
(b) Asbestos
(c) Mica
(d) Glass fibre
Ans: c
Which of the following parts of a transformer is visible from outside ?
(a) Bushings
(b) Core
(c) Primary winding
(d) Secondary winding
Ans: a
The noise produced by a transformer is termed as
(a) zoom
(b) hum
(c) ringing
(d) buzz
Ans: b
Which of the following loss in a transformer is zero even at full load ?
(a) Core loss
(b) Friction loss
(c) Eddy current loss
(d) Hysteresis loss
Ans: b
Which of the following is the most likely source of harmonics in a transformer ?
(a) poor insulation
(b) Overload
(c) loose connections
(d) Core saturation
Ans: d
If a transformer is continuously operated the maximum temperature rise will occur in
(a) core
(b) windings
(c) tank
(d) any of the above
Ans: b
The hum in a transformer is mainly attributed to
(a) load changes
(b) oil in the transformer
(c) magnetostriction
(d) mechanical vibrations
Ans: c
The maximum load that a power transformer can carry is limited by its
(a) temperature rise
(b) dielectric strength of oil
(c) voltage ratio
(d) copper loss
Ans: c
The efficiency of a transformer, under heavy loads, is comparatively low because
(a) copper loss becomes high in proportion to the output
(b) iron loss is increased considerably
(c) voltage drop both in primary and secondary becomes large
(d) secondary output is much less as compared to primary input
Ans: a
An open-circuit test on a transformer is conducted primarily to measure
(a) insulation resistance
(b) copper loss
(c) core loss
(d) total loss
(e) efficiency
(f) none of the above
Ans: c
A no-load test is performed on a transformer to determine
(a) core loss
(b) copper loss
(c) efficiency
(d) magnetising current
(e) magnetising current and loss
Ans: e
The voltage transformation ratio of a transformer is equal to the ratio of
(a) primary turns to secondary turns
(b) secondary current to primary current
(c) secondary induced e.m.f. to primary induced e.m.f.
(d) secondary terminal voltage to primary applied voltage
Ans: c
Part of the transformer which is most subject to damage from overheating is
(a) iron core
(b) copper winding
(c) winding insulation
(d) frame or case
(e) transformer tank
Ans: c
If a transformer is switched on to a voltage more than the rated voltage
(a) its power factor will deteriorate
(b) its power factor will increase
(c) its power factor will remain unaffected
(d) its power factor will be zero
Ans: a
Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is
(a) approximately equal to one
(b) less than one
(c) great than one
(d) none of the above
Ans: a
Minimum voltage regulation occurs when the power factor of the load is
(a) unity
(b) lagging
(c) leading
(d) zero
Ans: c
In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of
(a) less than 15 A
(b) more than 15 A
(c) 15 A
(d) none of the above
Ans: a
The efficiencies of transformers compared with that of electric motors of the same power are
(a) about the same
(6) much smaller
(c) much higher
(d) somewhat smaller
(e) none of the above
Ans: c

Polyphase Induction Motors

Which of the following component is usually fabricated out of silicon steel ?
(a) Bearings
(b) Shaft
(c) Statorcore
(d) None of the above
Ans: c
The frame of an induction motor is usually made of
(a) silicon steel
(b) cast iron
(c) aluminium
(d) bronze
Ans: b
The shaft of an induction motor is made of
(a) stiff
(b) flexible
(c) hollow
(d) any of the above
Ans: a
The shaft of an induction motor is made of
(a) high speed steel
(b) stainless steel
(c) carbon steel
(d) cast iron
Ans: c
In an induction motor, no-load the slip is generally
(a) less than 1%
(b) 1.5%
(c) 2%
(d) 4%
Ans: a
In medium sized induction motors, the slip is generally around
(a) 0.04%
(b) 0.4%
(c) 4%
(d) 14%
Ans: c
In squirrel cage induction motors, the rotor slots are usually given slight skew in order to
(a) reduce windage losses
(b) reduce eddy currents
(c) reduce accumulation of dirt and dust
(d) reduce magnetic hum
Ans: d
In case the air gap in an induction motor is increased
(a) the magnetising current of the rotor will decrease
(b) the power factor will decrease
(c) speed of motor will increase
(d) the windage losses will increase
Ans: b
Slip rings are usually made of
(a) copper
(b) carbon
(c) phospor bronze
(d) aluminium
Ans: c
A 3-phase 440 V, 50 Hz induction motor has 4% slip. The frequency of rotor e.m.f. will be
(a) 200 Hz
(b) 50 Hz
(c) 2 Hz
(d) 0.2 Hz
Ans: c
In Ns is the synchronous speed and s the slip, then actual running speed of an induction motor will be
(a) Ns
(b) s.N,
(c) (l-s)Ns
(d) (Ns-l)s
Ans: c

The efficiency of an induction motor can be expected to be nearly
(a) 60 to 90%
(b) 80 to 90%
(c) 95 to 98%
(d) 99%
Ans: b

The number of slip rings on a squirrel cage induction motor is usually
(a) two
(b) three
(c) four
(d) none
Ans: d
The starting torque of a squirrel-cage induction motor is
(a) low
(b) negligible
(c) same as full-load torque
(d) slightly more than full-load torque
Ans: a
A double squirrel-cage induction motor has
(a) two rotors moving in oppsite direction
(b) two parallel windings in stator
(c) two parallel windings in rotor
(d) two series windings in stator
Ans: c
Star-delta starting of motors is not possible in case of
(a) single phase motors
(b) variable speed motors
(c) low horse power motors
(d) high speed motors
Ans: a
The term ‘cogging’ is associated with
(a) three phase transformers
(b) compound generators
(c) D.C. series motors
(d) induction motors
Ans: d
In case of the induction motors the torque is
(a) inversely proportional to (Vslip)
(b) directly proportional to (slip)2
(c) inversely proportional to slip
(d) directly proportional to slip
Ans: d
An induction motor with 1000 r.p.m. speed will have
(a) 8 poles
(b) 6 poles
(c) 4 poles
(d) 2 poles
Ans: b
The good power factor of an induction motor can be achieved if the average flux density in the air gap is
(a) absent
(b) small
(c) large
(d) infinity
Ans: b
An induction motor is identical to
(a) D.C. compound motor
(b) D.C. series motor
(c) synchronous motor
(d) asynchronous motor
Ans: d
The injected e.m.f. in the rotor of induction motor must have
(a) zero frequency
(b) the same frequency as the slip frequency
(c) the same phase as the rotor e.m.f.
(d) high value for the satisfactory speed control
Ans: b
Which of the following methods is easily applicable to control the speed of the squirrel-cage induction motor ?
(a) By changing the number of stator poles
(b) Rotor rheostat control
(c) By operating two motors in cascade
(d) By injecting e.m.f. in the rotor circuit
Ans: a
The crawling in the induction motor is caused by
(a) low voltage supply
(b) high loads
(c) harmonics develped in the motor
(d) improper design of the machine
(e) none of the above
Ans: c
The auto-starters (using three auto transformers) can be used to start cage induction motor of the following type
(a) star connected only
(b) delta connected only
(c) (a) and (b) both
(d) none of the above
Ans: c
The torque developed in the cage induction motor with autostarter is
(a) k/torque with direct switching
(6) K x torque with direct switching
(c) K2 x torque with direct switching
(d) k2/torque with direct switching
Ans: c
When the equivalent circuit diagram of doouble squirrel-cage induction motor is constructed the two cages can be
considered
(a) in series
(b) in parallel
(c) in series-parallel
(d) in parallel with stator
Ans: b
It is advisable to avoid line-starting of induction motor and use starter because
(a) motor takes five to seven times its full load current
(b) it will pick-up very high speed and may go out of step
(c) it will run in reverse direction
(d) starting torque is very high
Ans: a
Stepless speed control of induction motor is possible by which of the following methods ?
(a) e.m.f. injection in rotor eueuit
(b) Changing the number of poles
(c) Cascade operation
(d) None of the above
Ans: b
Rotor rheostat control method of speed control is used for
(a) squirrel-cage induction motors only
(b) slip ring induction motors only
(c) both (a) and (b)
(d) none of the above
Ans: b
In the circle diagram for induction motor, the diameter of the circle represents
(a) slip
(b) rotor current
(c) running torque
(d) line voltage
Ans: b
For which motor the speed can be controlled from rotor side ?
(a) Squirrel-cage induction motor
(b) Slip-ring induction motor
(c) Both (a) and (b)
(d) None of the above
Ans: b
If any two phases for an induction motor are interchanged
(a) the motor will run in reverse direction
(b) the motor will run at reduced speed
(c) the motor will not run
(d) the motor will burn
Ans: a
An induction motor is
(a) self-starting with zero torque
(b) self-starting with high torque
(c) self-starting with low torque
(d) non-self starting
Ans: c
The maximum torque in an induction motor depends on
(a) frequency
(b) rotor inductive reactance
(c) square of supply voltage
(d) all of the above
Ans: d
In three-phase squirrel-cage induction motors
(a) rotor conductor ends are short-circuited through slip rings
(b) rotor conductors are short-circuited through end rings
(c) rotor conductors are kept open
(d) rotor conductors are connected to insulation
Ans: b
In a three-phase induction motor, the number of poles in the rotor winding is always
(a) zero
(b) more than the number of poles in stator
(c) less than number of poles in stator
(d) equal to number of poles in stator
Ans: d
DOL starting of induction motors is usually restricted to
(a) low horsepower motors
(b) variable speed motors
(c) high horsepower motors
(d) high speed motors
Ans: a
The speed of a squirrel-cage induction motor can be controlled by all of the following except
(a) changing supply frequency
(b) changing number of poles
(c) changing winding resistance
(d) reducing supply voltage
Ans: c
The ‘crawling” in an induction motor is caused by
(a) high loads
(6) low voltage supply
(c) improper design of machine
(d) harmonics developed in the motor
Ans: d
The power factor of an induction motor under no-load conditions will be closer to
(a) 0.2 lagging
(b) 0.2 leading
(c) 0.5 leading
(d) unity
Ans: a
The ‘cogging’ of an induction motor can be avoided by
(a) proper ventilation
(b) using DOL starter
(c) auto-transformer starter
(d) having number of rotor slots more or less than the number of stator slots (not equal)
Ans: d
If an induction motor with certain ratio of rotor to stator slots, runs at 1/7 of the normal speed, the phenomenon will be termed as
(a) humming
(b) hunting
(c) crawling
(d) cogging
Ans: c
Slip of an induction motor is negative when
(a) magnetic field and rotor rotate in opposite direction
(b) rotor speed is less than the synchronous speed of the field and are in the same direction
(c) rotor speed is more than the synchronous speed of the field and are in the same direction
(d) none of the above
Ans: c
Size of a high speed motor as compared to low speed motor for the same H.P. will be
(a) bigger
(b) smaller
(c) same
(d) any of the above
Ans: b
A 3-phase induction motor stator delta connected, is carrying full load and one of its fuses blows out. Then the motor
(a) will continue running burning its one phase
(b) will continue running burning its two phases
(c) will stop and carry heavy current causing permanent damage to its winding
(d) will continue running without any harm to the winding
Ans: a
A 3-phase induction motor delta connected is carrying too heavy load and one of its fuses blows out. Then the
motor
(a) will continue running burning its one phase
(b) will continue running burning its two phase
(c) will stop and carry heavy current causing permanent damage to its winding
(d) will continue running without any harm to the winding
Ans: c
Low voltage at motor terminals is due to
(a) inadequate motor wiring
(b) poorely regulated power supply
(c) any one of the above
(d) none of the above
Ans: c
In an induction motor the relationship between stator slots and rotor slots is that
(a) stator slots are equal to rotor slots
(b) stator slots are exact multiple of rotor slots
(c) stator slots are not exact multiple of rotor slots
(d) none of the above
Ans: c
Slip ring motor is recommended where
(a) speed control is required
(6) frequent starting, stopping and reversing is required
(c) high starting torque is needed
(d) all above features are required
Ans: d
As load on an induction motor goes on increasing
(a) its power factor goes on decreasing
(b) its power factor remains constant
(c) its power factor goes on increasing even after full load
(d) its power factor goes on increasing up to full load and then it falls again
Ans: d
If a 3-phase supply is given to the stator and rotor is short circuited rotor will move
(a) in the opposite direction as the direction of the rotating field
(b) in the same direction as the direction of the field
(c) in any direction depending upon phase squence of supply
Ans: b
It is advisable to avoid line starting of induction motor and use starter because
(a) it will run in reverse direction
(b) it will pick up very high speed and may go out of step
(c) motor takes five to seven times its full load current
(d) starting torque is very high
Ans: c
The speed characteristics of an induction motor closely resemble the speedload characteristics of which of the
following machines
(a) D.C. series motor
(b) D.C. shunt motor
(c) universal motor
(d) none of the above
Ans: b
Which type of bearing is provided in small induction motors to support the rotor shaft ?
(a) Ball bearings
(b) Cast iron bearings
(c) Bush bearings
(d) None of the above
Ans: a
A pump induction motor is switched on to a supply 30% lower than its rated voltage. The pump runs. What will
eventually happen ? It will
(a) stall after sometime
(b) stall immediately
(c) continue to run at lower speed without damage
(d) get heated and subsequently get damaged
Ans: d
5 H.P., 50-Hz, 3-phase, 440 V, induction motors are available for the following r.p.m. Which motor will be the
costliest ?
(a) 730 r.p.m.
(b) 960 r.p.m.
(c) 1440 r.p.m.
(d) 2880 r.p.m.
Ans: a
A 3-phase slip ring motor has
(a) double cage rotor
(6) wound rotor
(c) short-circuited rotor
(d) any of the above
Ans: b
The starting torque of a 3-phase squirrel cage induction motor is
(a) twice the full load torque
(b) 1.5 times the full load torque
(c) equal to full load torque
Ans: b
Short-circuit test on an induction motor cannot be used to determine
(a) windage losses
(b) copper losses
(c) transformation ratio
(d) power scale of circle diagram
Ans: a
In a three-phase induction motor
(a) iron losses in stator will be negligible as compared to that in rotor
(6) iron losses in motor will be neg¬ligible as compared to that in rotor
(c) iron losses in stator will be less than that in rotor
(d) iron losses in stator will be more than that in rotor
Ans: d
In case of 3-phase induction motors, plugging means
(a) pulling the motor directly on line without a starter
(b) locking of rotor due to harmonics
(c) starting the motor on load which is more than the rated load
(d) interchanging two supply phases for quick stopping
Ans: d
Which is of the following data is required to draw the circle diagram for an induction motor ?
(a) Block rotor test only
(b) No load test only
(c) Block rotor test and no-load test
(d) Block rotor test, no-load test and stator resistance test
Ans: d
In three-phase induction motors sometimes copper bars are placed deep in the rotor to
(a) improve starting torque
(b) reduce copper losses
(c) improve efficiency
(d) improve power factor
Ans: a
In a three-phase induction motor
(a) power factor at starting is high as compared to that while running
(b) power factor at starting is low as compared to that while running
(c) power factor at starting in the same as that while running
Ans: b
The vafcie of transformation ratio of an induction motor can be found by
(a) open-circuit test only
(b) short-circuit test only
(c) stator resistance test
(d) none of the above
Ans: b
The power scale of circle diagram of an induction motor can be found from
(a) stator resistance test
(6) no-load test only
(c) short-circuit test only
(d) noue of the above
Ans: c
The shape of the torque/slip curve of induction motor is
(a) parabola
(b) hyperbola
(c) rectangular parabola
(d) straigth line
Ans: c
A change of 4% of supply voltage to an induction motor will produce a change of appromimately
(a) 4% in the rotor torque
(b) 8% in the rotor torque
(c) 12% in the rotor torque
(d) 16% in the rotor torque
Ans: d
The stating torque of the slip ring induction motor can be increased by adding
(a) external inductance to the rotor
(b) external resistance to the rotor
(c) external capacitance to the rotor
(d) both resistance and inductance to rotor
Ans: b
A 500 kW, 3-phase, 440 volts, 50 Hz, A.C. induction motor has a speed of 960 r.p.m. on full load. The machine has 6 poles. The slip of the machine will be
(a) 0.01
(b) 0.02
(c) 0.03
(d) 0.04
Ans: d
The complete circle diagram of induetion motor can be drawn with the help of data found from
(a) noload test
(6) blocked rotor test
(c) stator resistance test
(d) all of the above
Ans: d
In the squirrel-cage induction motor the rotor slots are usually given slight skew
(a) to reduce the magnetic hum and locking tendency of the rotor
(b) to increase the tensile strength of the rotor bars
(c) to ensure easy fabrication
(d) none of the above
Ans: a
The torque of a rotor in an induction motor under running condition is maximum
(a) at the unit value of slip
(b) at the zero value of slip
(c) at the value of the slip which makes rotor reactance per phase equal to the resistance per phase
(d) at the value of the slip which makes the rotor reactance half of the rotor
Ans: c
What will happen if the relative speed between the rotating flux of stator and rotor of the induction motor is zero ?
(a) The slip of the motor will be 5%
(b) The rotor will not run
(c) The rotor will run at very high speed
(d) The torque produced will be very large
Ans: b
The circle diagram for an induction motor cannot be used to determine
(a) efficiency
(b) power factor
(c) frequency
(d) output
Ans: a
Blocked rotor test on induction motors is used to find out
(a) leakage reactance
(b) power factor on short circuit
(c) short-circuit current under rated voltage
(d) all of the above
Ans: d
Lubricant used for ball bearing is usually
(a) graphite
(b) grease
(c) mineral oil
(d) molasses
Ans: b
An induction motor can run at synchronous speed when
(a) it is run on load
(b) it is run in reverse direction
(c) it is run on voltage higher than the rated voltage
(d) e.m.f. is injected in the rotor circuit
Ans: d
Which motor is preferred for use in mines where explosive gases exist ?
(a) Air motor
(b) Induction motor
(c) D.C. shunt motor
(d) Synchronous motor
Ans: a
The torque developed by a 3-phase induction motor least depends on
(a) rotor current
(b) rotor power factor
(c) rotor e.m.f.
(d) shaft diameter
Ans: d
In an induction motor if air-gap is increased
(a) the power factor will be low
(b) windage losses will be more
(c) bearing friction will reduce
(d) copper loss will reduce In an induction motor
Ans: a
In induction motor, percentage slip depends on
(a) supply frequency
(b) supply voltage
(c) copper losses in motor
(d) none of the above
Ans: c
When /?2 is the rotor resistance, .X2 the rotor reactance at supply frequency and s the slip, then the condition for maximum torque under running conditions will be
(a) sR2X2 = 1
(b) sR2 = X2
(c) R2 = sX2
(d) R2 = s2X2
Ans: c
In case of a double cage induction motor, the inner cage has
(a) high inductance arid low resistance
(b) low inductance and high resistance
(c) low inductance and low resistance
(d) high inductance and high resistance
Ans: a
The low power factor of induction motor is due to
(a) rotor leakage reactance
(b) stator reactance
(c) the reactive lagging magnetizing current necessary to generate the magnetic flux
(d) all of the above
Ans: d
Insertion of reactance in the rotor circuit
(a) reduces starting torque as well as maximum torque
(b) increases starting torque as well as maximum torque
(c) increases starting torque but maxi-mum torque remains unchanged
(d) increases starting torque but maxi-mum torque decreases
Ans: a
Insertion of resistance in the rotcir of an induction motor to develop a given torque
(a) decreases the rotor current
(b) increases the rotor current
(c) rotor current becomes zero
(d) rotor current rernains same
Ans: d
For driving high inertia loods best type of induction motor suggested is
(a) slip ring type
(b) squirrel cage type
(c) any of the above
(d) none of the above
Ans: a
Temperature of the stator winding of a three phase induction motor is obtained by
(a) resistance rise method
(b) thermometer method
(c) embedded temperature method
(d) all above methods
Ans: d
The purpose of using short-circuit gear is
(a) to short circuit the rotor at slip rings
(b) to short circuit the starting resistances in the starter
(c) to short circuit the stator phase of motor to form star
(d) none of the above
Ans: a
In a squirrel cage motor the induced e.m.f. is
(a) dependent on the shaft loading
(b) dependent on the number of slots
(c) slip times the stand still e.m.f. induced in the rotor
(d) none of the above
Ans: c
Less maintenance troubles are experienced in case of
(a) slip ring induction motor
(6) squirrel cage induction motor
(c) both (a) and (b)
(d) none of the above
Ans: b
A squirrel cage induction motor is not selected when
(a) initial cost is the main consideration
(b) maintenance cost is to be kept low
(c) higher starting torque is the main consideration
(d) all above considerations are involved
Ans: c
Reduced voltage starter can be used with
(a) slip ring motor only but not with squirrel cage induction motor
(b) squirrel cage induction motor only but not with slip ring motor
(c) squirrel cage as well as slip ring induction motor
(d) none of the above
Ans: c
Slip ring motor is preferred over squirrel cage induction motor where
(a) high starting torque is required
(b) load torque is heavy
(c) heavy pull out torque is required
(d) all of the above
Ans: a
In a star-delta starter of an induction motor
(a) resistance is inserted in the stator
(b) reduced voltage is applied to the stator
(c) resistance is inserted in the rotor
(d) applied voltage perl stator phase is 57.7% of the line voltage
Ans: d
The torque of an induction motor is
(a) directly proportional to slip
(b) inversely proportional to slip
(c) proportional to the square of the slip
(d) none of the above
Ans: a
The rotor of an induction motor runs at
(a) synchronous speed
(b) below synchronous speed
(c) above synchronous speed
(d) any of the above
Ans: b
The starting torque of a three phase induction motor can be increased by
(a) increasing slip
(b) increasing current
(c) both (a) and (b)
(d) none of the above
Ans: c
Insertion of resistance in the stator of an induction motor
(a) increases the load torque
(b) decreases the starting torque
(c) increases the starting torque
(d) none of the above
Ans: b

Single Phase Induction Motors

In a split phase motor, the running winding should have
(a) high resistance and low inductance
(b) low resistance and high inductance
(c) high resistance as well as high inductance
(d) low resistance as well as low inductiance
Ans: b
If the capacitor of a single-phase motor is short-circuited
(a) the motor will not start
(b) the motor will run
(c) the motor will run in reverse direction
(d) the motor will run in the same direction at reduced r.p.m.
Ans: a
In capacitor start single-phase motors
(a) current in the starting winding leads the voltage
(b) current in the starting winding lags the voltage
(c) current in the starting winding is in phase with voltage in running winding
(d) none of the above
Ans: a
In a capacitor start and run motors the function of the running capacitor in series with the auxiliary winding is to
(a) improve power factor
(b) increase overload capacity
(c) reduce fluctuations in torque
(d) to improve torque
Ans: a
In a capacitor start motor, the phase displacement between starting and running winding can be nearly
(a) 10°
(b) 30°
(c) 60°
(d) 90°
Ans: d
In a split phase motor
(a) the starting winding is connected through a centrifugal switch
(b) the running winding is connected through a centrifugal switch
(c) both starting and running windings are connected through a centrifugal switch
(d) centrifugal switch is used to control supply voltage
Ans: a
The rotor developed by a single-phase motor at starting is
(a) more than i.he rated torque
(b) rated torque
(c) less than the rated torque
(d) zero
Ans: d
Which of the following motor will give relatively high starting torque ?
(a) Capacitor start motor
(b) Capacitor run motor
(c) Split phase motor
(d) Shaded pole motor
Ans: a
Which of the following motor will have relatively higher power factor ?
(a) Capacitor run motor
(b) Shaded pole motor
(c) Capacitor start motor
(d) Split phase motor
Ans: a
In a shaded pole motor, the shading coil usually consist of
(a) a single turn of heavy wire which is in parallel with running winding
(b) a single turn of heavy copper wire which is short-circuited and carries only induced current
(c) a multilayer fine gauge copper wire in parallel with running winding
(d) none of the above
Ans: b
In a shaded pole single-phase motor, the revolving field is produced by the use of
(a) inductor
(b) capacitor
(c) resistor
(d) shading coils
Ans: d
A centrifugal switch is used to dis- connect ‘starting winding when motor has
(a) run for about 1 minute
(b) run for about 5 minutes
(c) picked up about 50 to 70 per cent of rated speed
(d) picked up about 10 to 25 per cent of rated speed
Ans: c
If a particular application needs high speed and high starting torque, then which of the following motor will be preferred ?
(a) Universal motor
(b) Shaded pole type motor
(c) Capacitor start motor
(d) Capacitor start and run motor
Ans: a
The value of starting capacitor of a fractional horse power motor will be
(a) 100 uF
(6) 200 uF
(c) 300 uF
(d) 400 uF
Ans: c
In repulsion motor direction of rotation of motor
(a) is opposite to that of brush shift
(b) is the same as that of brush shift
(c) is independent of brush shift
Ans: b
In a single phase motor the centrifugal switch
(a) disconnects auxiliary winding of the motor
(b) disconnects main winding of the motor
(c) reconnects the main winding the motor
(d) reconnects the auxiliary winding of the motor
Ans: a
The running winding of a single phase motor on testing with meggar is found to be ground. Most probable location of the ground will be
(a) at the end connections
(b) at the end terminals
(c) anywhere on the winding inside a slot
(d) at the slot edge where coil enters or comes out of the slot
Ans: d
A capacitor-start single phase induction motor is switched on to supply with its capacitor replaced by an inductor of equivalent reactance value. It will
(a) start and then stop
(b) start and run slowly
(c) start and run at rated speed
(d) not start at all
Ans: d
Which of the following motors is used in mixies ?
(a) Repulsion motor
(b) Reluctance motor
(c) Hysteresis motor
(d) Universal motor
Ans: d
Which of the following motors is inherently self starting ?
(a) Split motor
(b) Shaded-pole motor
(c) Reluctance motor
(d) None of these
Ans: b
The direction of rotation of an hysteresis motor is determined by
(a) interchanging the supply leads
(b) position of shaded pole with respect to main pole
(c) retentivity of the rotor material
(d) none of these
Ans: b
Burning out of winding is due to
(a) short circuited capacitor
(b) capacitor value hiving changed
(c) open circuiting of capacitor
(d) none of the above
Ans: a
Direction of rotation of a split phase motor can be reversed by reversing the connection of
(a) running winding only
(b) starting winding only
(c) either (a) or (b)
(d) both (a) and (b)
Ans: c
Short-circuiter is used in
(a) repulsion induction motor
(b) repulsion motor
(c) repulsion start induction run motor
(d) none of the above
Ans: c
The range of efficiency for shaded pole motors is
(a) 95% to 99%
(b) 80% to 90%
(c) 50% to 75%
(d) 5% to 35%
Ans: d
In a capacitor start single-phase motor, when capacitor is replaced by a resistance
(a) torque will increase
(b) the motor will consume less power
(c) motor will run in reverse direction
(d) motor will continue to run in same direction
Ans: d
The power factor of a single-phase induction motor is usually
(a) lagging
(b) always leading
(c) unity
(d) unity to 0.8 leading
Ans: a
A shaded pole motor can be used for
(a) toys
(b) hair dryers
(c) circulators
(d) any of the above
Ans: d
A hysteresis motor works on the principle of
(a) hysteresis loss
(b) magnetisation of rotor
(c) eddy current loss
(d) electromagnetic induction
Ans: a
Which of the following motor will give the highest starting torque ?
(a) D.C. shunt motor
(b) Schrage motor
(c) Repulsion start and induction run motor
(d) Universal motor
Ans: b
For which of the applications a reluctance motor is preferred ?
(a) Electric shavers
(b) Refrigerators
(c) Signalling and timing devices
(d) Lifts and hoists
Ans: c
The motor used on small lathes is usually
(a) universal motor
(b) D.C. shunt motor
(c) single-phase capacitor run motor
(d) 3-phase synchronous motor
Ans: c
Which of the following motors is preferred for tape-recorders ?
(a) Shaded pole motor
(b) Hysteresis motor
(c) Two value capacitor motor
(d) Universal motor
Ans: b
A single-phase induction motor is
(a) inherently self-starting with high torque
(b) inherently self-starting with low torque
(c) inherently non-self-starting with low torque
(d) inherently non-self-starting with high torque
Ans: c
A schrage motor can run on
(a) zero slip
(b) negative slip
(c) positive slip
(d) all of the above
Ans: d
A universal motor can run on
(a) A.C. only
(6) D.C. only
(c) either A.C. or D.C.
(d) none of the above
Ans: c
Which of the following single-phase motors is suitable for timing and control purposes ?
(a) Reluctance motor
(b) Series motor
(c) Repulsion motor
(d) Universal motor
Ans: a
Single phase induction motor usually operates on
(a) 0.6 power factor lagging
(b) 0.8 power factor lagging
(c) 0.8 power factor leading
(d) unity power factor
Ans: a
In split-phase motor auxiliary winding is of
(a) thick wire placed at the bottom of the slots
(b) thick wire placed at the top of the slots
(c) thin wire placed at the top of the slots
(d) thin wire placed at the bottom of the slots
Ans: c
Which of the following motors will operate at high power factor ?
(a) Shaped pole motor
(b) Split phase motor
(c) Capacitor start motor
(d) Capacitor run motor
Ans: d
In a two value capacitor motor, the capacitor used for running purposes is
(a) air capacitor
(b) paper spaced oil filled type
(c) ceramic type
(d) a.c. electrolytic type
Ans: b
Which of the following motors can be run on AC. as well as D.C. supply ?
(a) Universal motor
(b) Repulsion motor
(c) Synchronous motor
(d) Reluctance motor
Ans: a
In A.C. series motor compensating winding is employed to
(a) reduce the effects of armature reaction
(b) increase the torque
(c) reduce sparking at the brushes
(d) none of the above
Ans: c
Which of the following single-phase induction motors is generally used in time phonographs ?
(a) Resistance start
(b) Capacitor start capacitor run
(c) Shaded pole
(d) Universal
Ans: c
Which of the following motors has highest starting torque ?
(a) Repulsion motor
(b) Shaped pole motor
(c) Capacitor-start motor
(d) Split-phase motor
Ans: c
The repulsion-start induction-run motor is used because of
(a) good power factor
(b) high efficiency
(c) minimum cost
(d) high starting torque
Ans: d
In case of a shaded pole motor the direction of rotation of the motor is
(a) from main pole to shaded pole
(b) from shaded pole to main pole
(c) either of the above depending on voltage
(d) either of the above depending on power factor
Ans: a
In case of high speed universal motor which of the following needs more attention ?
(a) End play
(b) Air gap
(c) Insulation in rotor
(d) Balancing of rotor
Ans: d
The wattage rating for a ceiling fan motor will be in the range
(a) 200 to 250 W
(b) 250 to 500 W
(c) 50 to 150 W
(d) 10 to 20 W
Ans: c
The wattage of motor for driving domestic sewing machine will be around
(a) 100 to 150 W
(b) 40 to 75 W
(c) 10 to 30 W
(d) 5 to 10 W
Ans: a
Which of the following single-phase motors has relatively poor starting torque ?
(a) Universal motor
(b) Repulsion motor
(c) Capacitor motor
(d) All single phase motors have zero starting torque
Ans: c
Which type of load is offered by cranes and hoists ?
(a) Gradually varying load
(b) Non-reversing, no-load start
(c) Reversing, light start
(d) Reversing, heavy start
Ans: d
The speed of a universal motor is generally reduced by using
(a) gear trains
(b) V-belts
(c) brakes
(d) chains
Ans: a
Which of the following motors can be used for unity power factor ?
(a) Capacitor run motor
(b) Shaded pole motor
(c) Hysteresis motor
(d) Schrage motor
Ans: d
When a D.C. series motor is connected to A.C. supply, the power factor will be low because of
(a) high inductance of field and armature circuits
(b) induced current in rotor due to variations of flux
(c) fine copper wire winding
(d) none of the above
Ans: a
The direction of rotation of universal motor can be reversed the by reversing the flow of current through
(a) armature winding
(b) field winding
(c) either armature winding or field winding
(d) none of the above
Ans: c
In which single-phase motor, the rotor has no teeth or winding ?
(a) Split phase motor
(b) Reluctance motor
(c) Hysteresis motor
(d) Universal motor
Ans: c
Which motor is normally free from mechanical and magnetic vibrations ?
(a) Split phase motor
(b) Universal motor
(c) Hysteresis motor
(d) Shaded pole motor
Ans: c
As hysteresis motors are free from mechanical and magnetic vibrations therefore these are considered as suitable for
(a) fans
(b) blowers
(c) sound equipment
(d) mixer grinders
Ans: c
A reluctance motor
(a) is self-starting
(b) is constant speed motor
(c) needs no D.C. excitation
(d) all of the above
Ans: d
In a hysteresis motor, the rotor must have
(a) retentivity
(b) resistivity
(c) susceptibility
(d) none of the above
Ans: a
The rotor of a hysteresis motor is made of
(a) aluminium
(b) cast iron
(c) chrome steel
(d) copper
Ans: c
The electric motor used in portable drills is
(a) capacitor run motor
(b) hysteresis motor
(c) universal motor
(d) repulsion motor
Ans: c
Which of the following applications always have some load whenever switched on ?
(a) Vacuum cleaners
(b) Fan motors
(c) Pistol drills
(d) All of the above
Ans: c
The speed control of universal motor used for sewing machines is by
(a) friction
(b) varying the resistance
(c) tapping the field
(d) centrifugal mechanism
Ans: b
Torque developed by a single phase induction motor at starting is
(a) pulsating
(b) uniform
(c) none of the above
(d) nil
Ans: d
In split phase motor main winding is of
(a) thin wire placed at the top of the slots
(b) thin wire placed at the bottom of the slots
(c) thick wire placed at the bottom of the slots
(d) thick wire placed at the top of the” slots
Ans: c
In repulsion motor, maximum torque is developed when
(a) brush axis is at 45° electrical to the field axis
(b) brush axis coincides with the field axis
(c) brush axis is at 90° electrical to the field axis
(d) none of the above
Ans: a
If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in
(a) damage to the starting winding
(b) damage to the centrifugal switch
(c) overloading of running winding
(d) none of the above
Ans: a
Speed torque characteristic of a repulsion induction motor is similar to that of a D.C.
(a) shunt motor
(b) series motor
(c) compound motor
(d) separately excited motor
Ans: c
In a ceilingfan employing capacitor run motor
(a) secondary winding surrounds the primary winding
(b) primary winding surrounds the secondary winding
(c) both are usual arrangements
(d) none of the above
Ans: a
The shaded pole motor is used for
(a) high starting torque
(b) low starting torque
(c) medium starting torque
(d) very high starting torque
Ans: b
The rotor slots, in an induction motor, are usually not quite parallel to the shaft because it
(a) improves the efficiency
(b) helps the rotor teeth to remain under the stator teeth
(c) helps in reducing the tendency of the rotor teeth to remain under the stator teeth
(d) improves the power factor
Ans: c
The speed/load characteristics of a universal motor is same as that of
(a) A.C. motor
(b) D.C. shunt motor
(c) D.C. series motor
(d) none of the above
Ans: c
The purpose of stator winding in the compensated repulsion motor is to
(a) provide mechanical balance
(b) improve power factor and provide better speed regulation
(c) prevent hunting in the motor
(d) eliminate armature reaction
Ans: b
Which of the following motors is used for unity power factor ?
(a) Hysteresis motor
(b) Schrage motor
(c) Universal motor
(d) Reluctance motor
Ans: b
The motor used for the compressors is
(a) d.c. series motor
(b) shaded pole motor
(c) capacitor-start capacitor-run motor
(d) reluctance motor
Ans: c
Which of the following motors is used in a situation where load increases with speed ?
(a) Induction motor
(b) Three-phase series motor
(c) Schrage motor
(d) Hysteresis motor
Ans: b
In repulsion motor, zero torque is developed when
(a) brush axis is 45° electrical to field axis
(b) brush axis coincides with the field axis
(c) brush axis is 90° electrical to field axis
(d) both (b) and (c)
Ans: d
Centrifugal switch disconnects the auxiliary winding of the motor at about ____ percent of synchronous speed
(a) 30 to 40
(b) 70 to 80
(c) 80 to 90
(d) 100
Ans: b
Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a
(a) magnetic relay
(b) thermal relay
(c) centrifugal switch
(d) none of the above
Ans: a
If a single phase induction motor runs slower than normal, the most likely defect is
(a) worn bearings
(b) short-circuit in the winding
(c) open-circuit in the winding
(d) none of the above
Ans: a
Which of the following motors is used in tape-recorders ?
(a) Hysteresis motor
(b) Reluctance motor
(c) Capacitor-run motor
(d) Universal motor
Ans: a
Which of the following statements regarding two value capacitor motor is incorrect ?
(a) It is a reversing motor
(b) It is preferred to permanent-split single-value capacitor motor where frequent reversals are required
(c) It has low starting as well as rushing currents
(d) It has high starting torque
Ans: b
Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners
because
(a) it is comparatively cheaper
(b) it has almost non-destructible capacitor
(c) it has low starting as well as running currents at relatively high power factor
(d) it is quiet in operation
Ans: c
If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then
(a) motor will not come up to speed
(b) motor will not carry the load
(c) current drawn by the motor will be excessively high
(d) electrolytic capacitor will, in all probability, suffer break down
Ans: d
In a universal motor, the most common cause of brush sparking is
(a) open armature winding
(b) shorted armature winding
(c) shorted field winding”
(d) high commutator mica
(e) all of the above
Ans: e
If starting winding of a single-phase induction motor is left in the circuit, it will
(a) run faster
(b) spark at light loads
(c) draw excessive current and overheat
(d) run slower
Ans: c
Most of the fractional horsepower motors have either
(a) hard and annealed bearings
(b) ball or roller bearings
(c) soft and porous bearings
(d) plain or sleeve bearings
Ans: d
Which of the following statements regarding reluctance-start motor is incorrect ?
(a) It is similar to reluctance motor
(b) It is basically an induction motor and not a synchronous one
(c) So far as its basic working principle is concerned, it is similar to shaded pole motor
(d) the air-gap between rotor and salient poles is non- uniform
Ans: a
To reverse the direction of rotation of acapacitor start motor while it is running we should
(a) disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding
(b) disconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding
(c) reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply
(d) reverse the direction of connections of the auxiliary winding and immediately connect it to supply
Ans: a
In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will
(a) become unstable
(b) draw excessive armature current and may burn out
(c) fall out of synchronism and come to stand still
(d) run as induction motor
Ans: d
Which of the following motors has two separate windings on the motor ?
(a) Repulsion motor
(b) Repulsion induction motor
(c) Repulsion start induction run motor
(d) None of the above
Ans: b
A shaded pole motor does not possess
(a) centrifugal switch
(b) capacitor
(c) commutator
(d) all of the above
Ans: d
In a A.C. series motor armature coils are usually connected to commutator
(a) through resistance
(b) through reactances
(c) through capacitors
(d) solidly
Ans: a
Which of the following statements regarding a reluctance motor is incorrect ?
(a) It cannot be reversed, ordinarily
(b) It requires no D.C. field excitation for its operation
(c) It is nothing else but a single-phase, salient pole synchronous-induction motor
(d) Its squirrel cage-rotor is of unsym-metrical magnetic construction in order to vary reluctance path between stator and rotor
Ans: a
A universal motor is one which
(a) can be operated either on D.C. or A.C. supply at approximately the same speed and output
(b) can be marketed internationally
(c) runs at dangerously high speed on no-load
Ans: a
A repulsion motor is equipped with
(a) slip rings
(b) commutator
(c) both (a) and (b)
(d) none of the above
Ans: b
The capacitors used in single-phase capacitor motors have no
(a) voltage rating
(b) dielectric medium
(c) polarity marking
(d) definite value
Ans: c
If a D.C. series motor is operated on A.C. supply, it will
(a) spark excessively
(b) have poor efficiency
(c) have poor power factor
(d) all of the above
Ans: d
After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on
(a) running winding
(b) rotor winding
(c) field winding
(d) compensating winding
Ans: a
Which of the following statements regarding repulsion-start induction motor is incorrect ?
(a) It requires more maintenance of commutator and other mechanical devices
(b) It makes quite a bit of noise on starting
(c) In fractional horse power motors, it has replaced the capacitor motors
(d) It is not easily reversed
Ans: c
A.C. series motor as compared to D.C. series motor has
(a) smaller brush width
(b) less number of field turns
(c) more number of armature turns
(d) less air gap
(e) all of the above
Ans: e
Locked rotor current of a shaded pole motor is
(a) equal to full load current
(b) less than full load current
(c) slightly more than full load current
(d) several times the full load current
Ans: c
Speed control of a universal motor is achieved by
(a) varying field flux with tapped field windings
(b) connecting rheostat in series
(c) applying variable voltage by means of silicon controlled rectifier
(d) applying variable voltage by means of variable auto-transformer
(e) all of the above methods
Ans: e
Hysteresis motor is particularly useful for high-quality record players and tape-recorders because
(a) it revolves synchronously
(b) it is not subject to any magnetic or mechanical vibrations
(c) it can be easily manufactured in extremely small sizes of up to 1 W output
(d) it develops hysteresis torque which is extremely steady both in amplitude and phase
Ans: d
Which of the following statements regarding hysteresis motor is in incorrect ?
(a) It is extremely sensitive to fluctuations in supply voltage
(b) Its high starting torque is due to its high rotor hysteresis loss
(c) It is extremely quiet in operation
(d) It accelerates from rest to full-speed almost instantaneously
Ans: a
Which of the following statements regarding single-phase induction motoris correct ?
(a) It requires only one winding
(b) It can rotate in one direction only
(c) It is self-starting
(d) It is not self-starting
Ans: d
The starting winding of a single-phase motor is placed in
(a) armature
(b) field
(c) rotor
(d) stator
Ans: d
The speed of a universal motor is usually reduced by using
(a) gearing
(b) belts
(c) brakes
(d) chains
Ans: a

Synchronous Motors

Synchronous motors are generally not self-starting because
(a) the direction of rotation is not fixed
(b) the direction of instantaneous torque reverses after half cycle
(c) startes cannot be used on these machines
(d) starting winding is not provided on the machines
Ans: b
In case one phase of a three-phase synchronous motor is short-circuited the motor will
(a) not start
(b) run at 2/3 of synchronous speed
(c) run with excessive vibrations
(d) take less than the rated load
Ans: a
A pony motor is basically a
(a) small induction motor
(b) D.C. series motor
(c) D.C. shunt motor
(d) double winding A.C./D.C. motor
Ans: a
A synchronous motor can develop synchronous torque
(a) when under loaded
(b) while over-excited
(c) only at synchronous speed
(d) below or above synchronous speed
Ans: c
A synchronous motor can be started by
(a) pony motor
(b) D.C. compound motor
(c) providing damper winding
(d) any of the above
Ans: d
A three-phase synchronous motor will have
(a) no slip-rings
(b) one slip-ring
(c) two slip-rings
(d) three slip-rings
Ans: c
Under which of the following conditions hunting of synchronous motor is likely to occur ?
(a) Periodic variation of load
(b) Over-excitation
(c) Over-loading for long periods
(d) Small and constant load
Ans: a
When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected
(a) the motor stops
(b) it runs as a reluctance motor at the same speed
(c) it runs as a reluctance motor at a lower speed
(d) none of the above
Ans: a
When V is the applied voltage, then the breakdown torque of a synchronous motor varies as
(a) V
(b) V312
(c) V2
(d) 1/V
Ans: a
The power developed by a synchronous motor will be maximum when the load angle is
(a) zero
(b) 45°
(c) 90°
(d) 120°
Ans: c
A synchronous motor can be used as a synchronous capacitor when it is
(a) under-loaded
(b) over-loaded
(c) under-excited
(d) over-excited
Ans: d
A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased
(a) power factor as well as armature current will decrease
(b) power factor as well as armature current will increase
(c) power factor will increase but armature current will decrease
(d) power factor will decrease and armature current will increase
Ans: d
Mostly, synchronous motors are of
(a) alternator type machines
(6) induction type machines
(c) salient pole type machines
(d) smooth cylindrical type machines
Ans: c
The synchronous motor is not inherently self-starting because
(a) the force required to accelerate the rotor to the synchronous speed in an instant is absent
(b) the starting device to accelerate the rotor to near synchronous speed is absent
(c) a rotating magnetic field does not have enough poles
(d) the rotating magnetic field is produced by only 50 Hz frequency currents
Ans: a
As the load is applied to a synchronous motor, the motor takes more armature current because
(a) the increased load has to take more current
(b) the rotor by shifting its phase backward causes motor to take more current
(c) the back e.m.f. decreases causing an increase in motor current
(d) the rotor strengthens the rotating field casuing more motor current
Ans: b
Synchronous motor always runs at
(a) the synchronous speed
(b) less than synchronous speed
(c) more than synchronous speed
(d) none of the above
Ans: a
An over-excited synchronous motor takes
(a) leading current
(b) lagging current
(c) both (a) and (b)
(d) none of the above
Ans: a
The working of a synchronous motor is similar to
(a) gear train arrangement
(b) transmission of mechancial power by shaft
(c) distribution transformer
(d) turbine
(e) none of the above
Ans: b
The minimum armature current of the synchronous motor corresponds to operation at
(a) zero power factor leading
(b) unity power factor
(c) 0.707 power factor lagging
(d) 0.707 power factor leading
Ans: b
In a synchronous motor, the magnitude of stator back e.m.f. £& depends on
(a) d.c. excitation only
(b) speed of the motor
(c) load on the motor
(d) both the speed and rotor flux
Ans: a
If load (or torque) angle of a 4-pole synchronous motor is 6° electrical, its value in mechanical degrees is
(a) 2
(b) 3
(c) 4
(d) 6
Ans: b
For V-curves for a synchronous motor the graph is drawn between
(a) field current and armature current
(b) terminal voltage and load factor
(c) power factor and field current
(d) armature current and power factor
Ans: a
The back e.m.f. of a synchronous motor depends on
(a) speed
(b) load
(c) load angle
(d) all of the above
Ans: c
A synchronous motor can operate at
(a) lagging power factor only
(6) leading power factor only
(c) unity power factor only
(d) lagging, leading and unity power factors
Ans: d
In a synchronous motor which loss varies with load ?
(a) Windage loss
(b) Bearing friction loss
(c) Copper loss
(d) Core loss
Ans: c
A synchronous motor can be made self starting by providing
(a) damper winding on rotor poles
(b) damper winding on stator
(c) damper winding on stator as well as rotor poles
(d) none of the above
Ans: d
The oscillations in a synchronous motor can be damped out by
(a) maintaining constant excitation
(b) running the motor on leading power factors
(c) providing damper bars in the rotor pole faces
(d) oscillations cannot be damped
Ans: c
The shaft of synchronous motor is made of
(a) mild steel
(b) chrome steel
(c) alnico
(d) stainless steel
Ans: a
When the field of a synchronous motor is under-excited, the power factor will be
(a) leading
(b) lagging
(c) unity
(d) zero
Ans: b
The speed regulation of a synchronous motor is always
(a) 1%
(b) 0.5%
(c) positive
(d) zero
Ans: d
The percentage slip in case of a synchronous motor is
(a) 1%
(b) 100%
(c) 0.5%
(d) zero
Ans: d
The operating speed of a synchronous motor can be changed to new fixed value by
(a) changing the load
(b) changing the supply voltage
(c) changing frequency
(d) using brakes
Ans: c
A synchronous motor will always stop when
(a) supply voltage fluctuates
(b) load in motor varies
(c) excitation winding gets disconnected
(d) supply voltage frequency changes9885859805
Ans: c
riunting in a synchronous motor takes place
(a) when supply voltage fluctuates
(b) when load varies
(c) when power factor is unity
(d) motor is under loaded
Ans: b
When load on an over-excited or under excited synchronous*motor is increased, rate of change of its armature current as compared with that of power factor is
(a) more
(b) less
(c) equal
(d) twice
Ans: b
The rotor copper losses, in a synchronous motor, are met by
(a) d.c. source
(b) armature input
(c) motor input
(d) supply lines
Ans: a
The maximum power developed in a synchronous motor occurs at a coupling angle of
(a) 30°
(b) 60°
(c) 90°
(d) 180°
Ans: c
When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor
(a) remains same as the original value
(b) decreases to half the original value
(c) tends to becomes zero
(d) increases to two times the original value
Ans: d
In which of the following motors the stator and rotor magnetic field rotate at the same speed ?
(a) Universal motor
(b) Synchronous motor
(c) Induction motor
(d) Reluctance motor
Ans: b
Synchronsizingpower of a synchronous machine is
(a) direcly proportional to the synchronous reactance
(6) inversely proportional to the synchronous reactance
(a) equal to the synchronous reactance
(d) none of the above
Ans: b
Synchronous motors are
(a) not-self starting
(b) self-starting
(c) essentially self-starting
(d) none of the above
Ans: a
The standard full-load power factor ratings for synchronous motors are
(a) zero or 0.8 leading
(b) unity or 0.8 lagging
(c) unity or 0.8 leading
(d) unity or zero
Ans: c
A synchronous motor running with normal excitation adjusts to load increases essentially by increase in
(a) back e.m.f.
(b) armature current
(c) power factor
(d) torque angle
Ans: b
A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because
(a) synchronous motor has no slip
(b) stator supply is not required to produce magnetic field
(c) mechanical load on the rotor remains constant
(d) synchronous motor has large airgap
Ans: b
A synchronous motor working at leading power factor can be used as
(a) voltage booster
(b) phase advancer
(c) noise generator
(d) mechanical synchronizer
Ans: b
Slip rings are usually made of
(a) carbon or graphite
(b) brass or steel
(c) silver or gold
(d) copper or aluminium
Ans: b
An over excited synchronous motor is used for
(a) fluctuating loads
(b) variable speed loads
(c) low torque loads
(d) power factor corrections
Ans: d
When the voltage applied to a synchronous motor is increased, which of the following will reduce ?
(a) Stator flux
(b) Pull in torque
(c) Both (a) and (b)
(d) None of the above
Ans: d
The efficiency of a properly designed synchronous motor will usually fall in range
(a) 60 to 70%
(6) 75 to 80%
(c) 85 to 95%
(d) 99 to 99.5%
Ans: c
To limit the operating temperature an electrical machine should have proper
(a) voltage rating
(b) current rating
(c) power factor
(d) speed
Ans: b
Slip-rings in a synchronous motor carry
(a) direct current
(b) alternating current
(c) no current
(d) all of the above
Ans: a
A synchronous machine with large air gap has
(a) a higher value of stability limit
(6) a small value of inherent regulation
(c) a higher synchronizing power which makes the machine less sensitive to load variations
(d) all of the above
Ans: d
The armature current of the synchronous motor has higher values for
(a) high excitation only
(b) low excitation only
(c) both (a) and (b)
(d) none of the above
Ans: c
In a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately
(a) one-third
(b) twice
(c) thrice
(d) six times
(e) nine times
Ans: c
The angle between the rotating stator flux and rotor poles is called _____ angle.
(a) torque
(b) obtuse
(c) synchronizing
(d) power factor
Ans: a
Which of the following methods is used to start a synchronous motor ?
(a) Damper winding
(b) Star-delta starter
(c) Damper winding in conjunction with star-delta starter
(d) Resistance starter in the armature circuit
Ans: c
When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop
(a) inductor motor torque
(b) induction generator torque
(c) synchronous motor torque
(d) d.c. motor toque
(e) none of the above
Ans: b
An important advantage of a synchronous motor over wound round induction motor is that
(a) its power factor may be varied at will
(b) its speed is independent of supply frequency
(c) its speed may be controlled more easily
(d) none of the above
Ans: a
The mechanical displacement of the rotor with respect to the stator, in polyphase multipolar synchronous motors running at full load, is of the order of
(a) zero degree
(b) two degrees
(c) five degrees
(d) ten degrees
Ans: c
Power factor of a synchronous motor is unity when
(a) the armature current is maximum
(b) the armature current is minimum
(c) the armature current is zero
(d) none of the above
Ans: b
Change of D.C. excitation of a synchronous motor changes
(a) applied voltage of the motor
(b) motor speed
(c) power factor of power drawn by the motor
(d) any of the above
(e) all of the above
Ans: c
While starting a synchronous motor by induction motor action, field winding is usually
(a) connected to D.C. supply
(b) short-circuited by low resistance
(c) kept open-circuited
(d) none of the above
Ans: b
Which of the following motors will be used in electric clocks ?
(a) D.C. shunt motor
(b) D.C. series motor
(c) A.C. induction motor
(d) A.C. synchronous motor
Ans: d
If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor
(a) become more
(b) become less
(c) remain constant
(d) none of the above
Ans: b
A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will
(a) remain same
(b) go down
(c) improve
(d) none of the above
Ans: c
While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerting torque is produced by
(a) induction motor torque in field winding
(b) induction motor torque in damper winding
(c) eddy current and hysteresis torque in pole faces
(d) reHetance motor torque due to saliency of the rotor
(e) all of the above methods
Ans: e
Armature of a synchronous machine is
(a) of reducing number of slip rings on the rotor
(b) armature is associated with large power as compared to the field circuits
(c) of difficulty of providing high voltage insulation on rotor
(d) all of the above reasons
Ans: d
If excitation of a synchronous motor running with a constant load is decreased from its normal value, ignoring effects of armature reaction, it leads to
(a) increase in both armature current and power factor angle
(b) increase in back e.m.f. but decrease in armature current
(c) increase in both armature current and power factor which is lagging
(d) increase in torque angle but decrease in back e.m.f.
Ans: a
When a 3-phase synchronous generator is supplying a zero power factor lagging load, the armature field affects the main field in the following way
(a) augments it directly
(b) directly opposes it
(c) cross-magnetises it
(d) none of the above
Ans: b
Stability of a synchronous machine
(a) decreases with increase in its excitation
(b) increases with increase in its excitation
(c) remains unaffected with increase in excitation
(d) any of the above
Ans: b
The power factor of a synchronous motor is better than that of induction motor because
(a) stator supply is relieved of responsibility of producing magnetic field
(b) mechanical load on the motor can be adjusted
(c) synchronous motor runs at synchronous speed
(d) synchronous motor has large air gap
Ans: a
If in a synchronous motor, driving a given mechanical load and drawing current at a leading power factor from constant voltage supply its field excitation is increased, its power factor
(a) will become more
(b) will become less
(c) will remain unchanged
(d) none of the above.
Ans: b
A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because
(a) speed of the motor is reduced
(b) power factor is decreased
(c) Eb (back e.m.f.) becomes less than V (applied voltage)
(d) Er (net resultant voltage) in armature is increased
(e) none of the above
Ans: d
If one-phase of a 3-phase synchronous motor is short-circuited, motor
(a) will refuse to start
(b) will overheat in spots
(c) will not come upto speed
(d) will fail to pull into step
Ans: a
If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then
(a) it runs at a slower speed
(b) the motor stops
(c) it continues to run at the same speed
(d) it runs at a very high speed
Ans: b
In which of the following motors the stator and rotor fields rotate simultaneously ?
(a) D.C. motor
(b) Reluctance motor
(c) Universal motor
(d) Synchronous motor
(e) Induction motor
Ans: d
The speed of a synchronous motor
(a) increases as the load increases
(b) decreases as the load decreases
(c) always remains constant
(d) none of the above
Ans: c
A rotory converter can also be run as a
(a) d.c. shunt motor
(b) d.c. series motor
(c) d.c. compound motor
(d) induction motor
(e) synchronous motor
Ans: e
The maximum speed variation in a 3-phase synchronous motor is
(a) 10 per cent
(b) 6 per cent
(c) 4 per cent
(d) 2. per cent
(e) zero
Ans: e
Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor ?
(a) Phase to phase winding resistance
(b) Stator winding to earthed frame
(c) Rotor winding to earthed shaft
(d) All of the above
Ans: d
Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current ?
(a) High field current
(b) Low short circuit ratio
(c) High core losses
(d) Low field current
Ans: d

In a 3-phase synchronous motor, the negative phase sequence exists when the motor is
(a) supplied with unbalanced voltage
(b) under-loaded
(c) over-loaded
(d) none of the above
Ans: a
In a synchronous motor, damper windings are provided on
(a) stator frame
(b) rotor shaft
(c) pole faces
(d) none of the above
Ans: c
The induced e.m.f. in a synchronous motor working on leading power factor will be
(a) more than the supply voltage
(b) less than the supply voltage
(c) equal to the supply voltage
Ans: a
The effect of increasing the load on a synchronous motor running with normal excitation is to
(a) decrease both armature current and power factor
(6) decrease armature current but increase power factor
(c) increase armature current but decrease power factor
(d) increase both its armature current and power factor
Ans: c
The net armature voltage of a synchronous motor is equal to the
(a) vector sum of Eb and V
(b) arithmetic sum of Eb and V
(c) arithmetic difference of Eb and V
(d) vector difference of Eh and V
Ans: d
The ratio of starting torque to running torque in a synchronous motor is
(a) zero
(b) one
(c) two
(d) infinity
Ans: a
In a synchronous motor, the magnitude of stator back e.m.f. Eb depends on
(a) load on the motor
(b) d.c. excitation only
(c) both the speed and rotor flux
(d) none of the above
Ans: b
A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed
(a) the motor will stop
(b) the motor continue to run in the same direction
(c) the winding of the motor will burn
(d) the motor will run in the reverse direction
(e) none of the above
Ans: b
The magnitude of field flux in a 3-phase synchronous motor
(a) remains constant at all loads
(b) varies with speed
(c) varies with the load
(d) varies with power factor
Ans: a
The torque angle, in a synchronous motor, is the angle between
(a) the supply voltage and the back e.m.f.
(b) magnetising current and back e.m.f.
(c) the rotating stator flux and rotor poles
(d) none of the above
Ans: c
Hunting in a synchronous motor cannot be due to
(a) windage friction
(b) variable load
(c) variable frequency
(d) variable supply voltage
Ans: a
By which of the following methods the constant speed of a synchronous motor can be changed to new fixed value ?
(a) By changing the supply frequency
(b) By interchanging any two phases
(c) By changing the applied voltage
(d) By changing the load.
Ans: a
In a synchronous motor, V-curves represent relation between
(a) armature current and field current
(b) power factor and speed
(c) field current and speed
(d) field current and power factor
Ans: a
In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be
(a) 3000 r.p.m.
(b) 1500 r.p.m.
(c) 750 r.p.m.
(d) none of the above
Ans: b
A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have
(a) no change of power factor
(b) lagging power factor with over-excitation
(c) leading power factor with under-excitation
(d) leading power factor with over-excitation
Ans: d
Which of the following motors is non-self starting ?
(a) D.C. series motor
(b) synchronous motor
(c) Squirrel cage induction motor
(d) Wound round induction motor
Ans: b
In a synchronous motor it the back e.m.f. generated in the armature at noload is approximately equal to the applied voltage, then
(a) the motor is said to be fully loaded
(b) the torque generated is maximum
(c) the excitation is said to be zero per cent
(d) the excitation is said to be hundred per cent
Ans: d
In a synchronous motor, the damping winding is generally used to
(a) prevent hunting and provide the starting torque
(b) reduce the eddy currents
(c) provide starting torque only
(d) reduce noise level
(e) none of the above
Ans: a
If the field of a synchronous motor is underexcited, the power factor will be
(a) zero
(b) unity
(c) lagging
(d) leading
Ans: c
The back e.m.f. in the stator of a synchronous motor depends on
(a) number of poles
(b) flux density
(c) rotor speed
(d) rotor excitation
(e) none of the above
Ans: d
The maximum value of torque that a synchronous motor can develop without losing its synchronism, is known as
(a) slip torque
(b) pull-out torque
(c) breaking torque
(d) synchronising torque
Ans: d
In a synchronous motor, the armature current has large values for
(a) high excitation only
(b) low excitation only
(c) both high and low excitation
(d) none of the above
Ans: c
Which of the following losses, in a synchronous motor, does not vary with load?
(a) Windage loss
(b) Copper losses
(c) Any of the above
(d) None of the above
Ans: a
The size of a synchronous motor decreases with the increase in
(a) flux density
(b) horse power rating
(c) speed
(d) all of the above
Ans: a
Which of the following losses is not dissipated by the stator core surface in a synchronous motor ?
(a) Eddy current losses in the conductors
(b) Iron losses in the stator
(c) Copper losses in the slot portion of the conductors
(d) Windage losses
(e) None of the above
Ans: d
The duration of sudden snort-circuit test on a synchronous motor is usually about
(a) one hour
(b) one minute
(c) one second
(d) none of the above
Ans: c
The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as
(a) pull-up torque
(b) pull-in torque
(c) pull-out torque
(d) none of the above
Ans: b
A synchronous machine with low value of short-circuit ratio has
(a) lower stability limit
(6) high stability limit
(c) good speed regulation
(d) good voltage regulation
(e) none of the above
Ans: a
The construction of a synchronous motor resembles
(a) a series motor
(b) an induction motor
(c) an alternator
(d) a rotary converter
Ans: c
If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will
(a) stop
(b) run as induction motor
(c) function as static condenser
(d) burn with dense smoke
Ans: a
For power factor correction, synchronous motors operate at
(a) no-load and greatly over-excited fields
(b) no-load and under-excited fields
(c) normal load with minimum excitation
(d) normal load with zero excitation
Ans: a
The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as
(a) locked-rotor torque
(b) synchronous torque
(c) pull up torque
(d) reluctance torque
Ans: a
Exciters of synchronous machines are
(a) d.c. shunt machines
(b) d.c. series machines
(c) d.c. compound machines
(d) any of the above
Ans: a
The coupling angle or load angle of synchronous motor is defined as the angle between the
(a) rotor and stator teeth
(b) rotor and the stator poles of opposite polarity
(c) rotor and the stator poles of the same polarity
(d) none of the above
Ans: b
If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss
then
(a) the stator current will be zero
(b) the stator current will be very small
(c) the stator current will be very high
(d) the back e.m.f. will be more than the supply voltage
(e) none of the above
Ans: a

The maximum power developed in a synchronous motor will depend on
(a) the rotor excitation only
(b) the supply voltage only
(c) the rotor excitation and supply volt-age both
(d) the rotor excitation, supply voltage and maximum value of coupling angle (90°)
(e) none of the above
Ans: d
A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as
(a) static condenser
(b) condenser
(c) synchronous condenser
(d) none of the above
Ans: c
A synchronous motor develops maximum power when load angle is
(a) 45°
(b) 60°
(c) 90°
(d) 120°
Ans: c
In a synchronous motor, the breakdown torque is
(a) directly proportional to applied voltage
(b) directly proportional to the square of the applied voltage
(c) inversely proportional to applied voltage
(d) none of the above
Ans: a

Rectifiers & Converters

Which of the following are the applications of D.C. system ?
(a) Battery charging work
(b) Arc welding
(c) Electrolytic and electro-chemical processes
(d) Arc lamps for search lights
(e) All of the above
Ans: e
Which of the following methods may be used to convert A.C. system to D.C. ?
(a) Rectifiers
(b) Motor converters
(c) Motor-generator sets
(d) Rotary converters
(e) All of the above
Ans: e
In a single phase rotary converter the number of slip rings will be
(a) two
(b) three
(c) four
(d) six
(e) none
Ans: a
A synchronous converter can be started
(a) by means of a small auxiliary motor
(b) from AC. side as induction motor
(c) from D.C. side as D.C. motor
(d) any of the above methods
(e) none of the above methods
Ans: d
A rotary converter is a single machine with
(a) one armature and one field
(b) two armatures and one field
(c) one armature and two fields
(d) none of the above
Ans: a
A rotary converter combines the function of
(a) an induction motor and a D.C. generator
(b) a synchronous motor and a D.C. generator.
(c) a D.C. series motor and a D.C. generator
(d) none of the above
Ans: b
Which of the following is reversible in action ?
(a) Motor generator set
(b) Motor converter
(c) Rotary converter
(d) Any of the above
(e) None of the above
Ans: c
Which of the following metals is generally manufactured by electrolysis process ?
(a) Load
(b) Aluminium
(c) Copper
(d) Zinc
(e) None of the above
Ans: b
9. With a motor converter it is possible to obtain D.C. voltage only upto
(a) 200-100 V
(6) 600—800 V
(c) 1000—1200 V
(d) 1700—2000 V
Ans: d
Normally, which of the following is used, when a large-scale conversion from AC. to D.C. power is required ?
(a) Motor-generator set
(b) Motor converter
(c) Rotary converter
(d) Mercury arc rectifier
Ans: d
A rotary converter in general construction and design, is more or less like
(a) a transformer
(b) an induction motor
(c) an alternator
(d) any D.C. machine
Ans: d
A rotary converter operates at a
(a) low power factor
(6) high power factor
(c) zero power factor
(d) none of the above
Ans: b
In which of the following appUcations, direct current is absolutely essential ?
(a) Illumination
(b) Electrolysis
(c) Variable speed operation
(d) Traction
Ans: b
Which of the following AC. motors is usually used in large motor-generator sets?
(a) Synchronous motor
(b) Squirrel cage induction motor
(c) Slip ring induction motor
(d) Any of the above
Ans: a
In a rotary converter armature currents are
(a) d.c. only
(b) a.c. only
(c) partly a.c. and partly d.c.
Ans: c
In which of the following equipment direct current is needed ?
(a) Telephones
(b) Relays
(c) Time switches
(d) All of the above
Ans: d
In a rotary converter I2R losses as compared to a D.C. generator of the same size will be
(a) same
(b) less
(c) double
(d) three times
Ans: b
In a mercury arc rectifier positive ions are attracted towards
(a) anode
(b) cathode
(c) shell bottom
(d) mercury pool
Ans: b
Mercury, in arc rectifiers, is chosen for cathode because
(a) its ionization potential is relatively low
(b) its atomic weight is quite high
(c) its boiling point and specific heat are low
(d) it remains in liquid state at ordi¬nary temperature
(e) all of the above
Ans: e
The ionization potential of mercury is approximately
(a) 5.4 V
(b) 8.4 V
(c) 10.4 V
(d) 16.4 V
Ans: c
The potential drop in the arc, in a mercury arc rectifier, varies
(a) 0.05 V to 0.2 V per cm length of the arc
(b) 0.5 V to 1.5 V per cm length of the arc
(c) 2 V to 3.5 V per cm length of the arc
(d) none of the above
Ans: d
The voltage drop between the anode and cathode, of a mercury arc rectifier comprises of the following
(a) anode drop and cathode drop
(b) anode drop and arc drop
(c) cathode drop and arc drop
(d) anode drop, cathode drop and arc drop
Ans: d
Glass rectifiers are usually made into units capable of D.C. output (maximum continuous rating) of
(a) 100 A at 100 V
(b) 200 A at 200 V
(c) 300 A at 300 V
(d) 400 A at 400 V
(e) 500 A at 500 V
Ans: e
The voltage drop at anode, in a mercury arc rectifier is due to
(a) self restoring property of mercury
(b) high ionization potential
(c) energy spent in overcoming the electrostatic field
(d) high temperature inside the rectifier
Ans: c
The internal efficiency of a mercury arc rectifier depends on
(a) voltage only
(b) current only
(c) voltage and current
(d) r.m.s. value of current
(e) none of the above
Ans: a
If cathode and anode connections in a mercury arc rectifier are inter changed
(a) the rectifier will not operate
(b) internal losses will be reduced
(c) both ion and electron streams will move in the same direction
(d) the rectifier will operate at reduced efficiency
Ans: a
The cathdde voltage drop, in a mercury arc rectifier, is due to
(a) expenditure of energy in ionization
(b) surface resistance
(c) expenditure of energy in overcoming the electrostatic field
(d) expenditure of energy in liberating electrons from the mercury
Ans: d
To produce cathode spot in a mercury arc rectifier
(a) anode is heated
(b) tube is evacuated
(c) an auxiliary electrode is used
(d) low mercury vapour pressures are used
Ans: c
The advantage of mercury arc rectifier is that
(a) it is light in weight and occupies small floor space
(b) it has high efficiency
(c) it has high overload capacity
(d) it is comparatively noiseless
(e) all of the above
Ans: e
In a mercury pool rectifier, the voltage drop across its electrodes
(a) is directly proportional to load
(b) is inversely proportional to load
(c) varies exponentially with the load current
(d) is almost independent of load current
Ans: d
In a three-phase mercury arc rectifiers each anode conducts for
(a) one-third of a cycle
(b) one-fourth of a cycle
(c) one-half a cycle
(d) two-third of a cycle
Ans: a
In a mercury arc rectifier characteristic blue luminosity is due to
(a) colour of mercury
(b) ionization
(c) high temperature
(d) electron streams
Ans: b
Which of the following mercury arc rectifier will deliver least undulating current?
(a) Six-phase
(b) Three-phase
(c) Two-phase
(d) Single-phase
Ans: a
In a glass bulb mercury arc rectifier the maximum current rating is restricted to
(a) 2000 A
(b) 1500 A
(c) 1000 A
(d) 500 A
Ans: d
In a mercury arc rectifier______ flow from anode to cathode
(a) ions
(b) electrons
(c) ions and electrons
(d) any of the above
Ans: a
When a rectifier is loaded which of the following voltage drops take place ?
(a) Voltage drop in transformer reactance
(6) Voltage drop in resistance of transformer and smoothing chokes
(c) Arc voltage drop
(d) All of the above
Ans: d
On which of the following factors the number of phases for which a rectifier should be designed depend ?
(a) The voltage regulation of the rec¬tifier should be low
(b) In the output circuit there should be no harmonics
(c) The power factor of the system should be high
(d) The rectifier supply transformer should be utilized to the best ad-vantage
(e) all of the above
Ans: e
A mercury arc rectifier possesses ________ regulation characteristics
(a) straight line
(b) curved line
(c) exponential
(d) none of the above
Ans: d
It is the_______of the transformer on which the magnitude of angle of overlap depends.
(a) resistance
(b) capacitance
(c) leakage reactance
(d) any of the above
Ans: c
In a grid control of mercury arc rectifiers when the grid is made positive relative to cathode, then it the electrons on their may to anode.
(a) accelerates
(b) decelerates
(c) any of the above
(d) none of the above
Ans: a
In mercury arc rectifiers having grid, the arc can be struck between anode and cathode only when the grid attains a certain potential, this potential being known as
(a) maximum grid voltage
(b) critical grid voltage
(c) any of the above
(d) none of the above
Ans: b
In phase-shift control method the control is carried out by varying the of grid voltage.
(a) magnitude
(b) polarity
(c) phase
(d) any of the above
(e) none of the above
Ans: c

16.44. In a phase-shift control method, the phase shift between anode and grid voltages can be achieved by means of
(a) shunt motor
(6) synchronous motor
(c) induction regulator
(d) synchronous generator
Ans: c
45. The metal rectifiers are preferred to valve rectifiers due to which of the following advantages ?
(a) They are mechanically strong
(b) They do not require any voltage for filament heating
(c) Both (a) and (b)
(d) None of the above
Ans: c

Which of the following statement is incorrect ?
(a) Copper oxide rectifier is a linear device
(b) Copper oxide rectifier is not a perfect rectifier
(c) Copper oxide rectifier has a low efficiency
(d) Copper oxide rectifier finds use in control circuits
(e) Copper oxide rectifier is not stable during early life
Ans: a
The efficiency of the copper oxide rectifier seldom exceeds
(a) 90 to 95%
(b) 85 to 90%
(c) 80 to 85%
(d) 65 to 75%
Ans: d
Copper oxide rectifier is usually designed not to operate above
(a) 10°C
(b) 20°C
(c) 30°C
(d) 45°C
Ans: d
Selenium rectifier can be operated at temperatures as high as
(a) 25°C
(b) 40°C
(c) 60°C
(d) 75°C
Ans: d
In selenium rectifiers efficiencies ranging from ______ to ______ percent are attainable
(a) 25, 35
(b) 40, 50
(c) 60, 70
(d) 75, 85
Ans: d
Ageing of a selenium rectifier may change the output voltage by
(a) 5 to 10 per cent
(b) 15 to 20 per cent
(c) 25 to 30 per cent
(d) none of the above
Ans: a
The applications of selenium rectifiers are usually limited to potential of
(a) 10 V
(b) 30 V
(c) 60 V
(d) 100 V
(e) 200 V
Ans: d
Which of the following rectifiers have been used extensively in supplying direct current for electroplating ?
(a) Copper oxide rectifiers
(b) Selenium rectifiers
(c) Mercury arc rectifiers
(d) Mechanical rectifiers
(e) None of the above
Ans: b
A commutating rectifier consists of commutator driven by
(a) an induction motor
(b) a synchronous motor
(c) a D.C. series motor
(d) a D.C. shunt motor
Ans: b
Which of the following rectifiers are primarily used for charging of low voltage batteries from AC. supply ?
(a) Mechanical rectifiers
(b) Copper oxide rectifiers
(c) Selenium rectifiers
(d) Electrolytic rectifiers
(e) Mercury arc rectifiers
Ans: d
The efficiency of an electrolytic rectifier is nearly
(a) 80%
(b) 70%
(c) 60%
(d) 40%
Ans: c
Which of the following is the loss within the mercury arc rectifier chamber ?
(a) Voltage drop in arc
(6) Voltage drop at the anode
(c) Voltage drop at the cathode
(d) All of the above
Ans: d
The metal rectifiers, as compared to mercury arc rectifiers
(a) operate on low temperatures
(b) can operate on high voltages
(c) can operate on heavy loads
(d) give poor regulation
(e) none of the above
Ans: a
In a mercury arc rectifier, the anode is usually made of
(a) copper
(b) aluminium
(c) silver
(d) graphite
(e) tungsten
Ans: d
The ignited or auxiliary anode in mercury arc rectifier is made of
(a) graphite
(b) boron carbide
(c) aluminium
(d) copper
Ans: b

Power Plant Engineering

The commercial sources of energy are
(a) solar, wind and biomass
(b) fossil fuels, hydropower and nuclear energy
(c) wood, animal wastes and agriculture wastes
(d) none of the above
Ans: b
In India largest thermal power station is located at
(a) Kota
(b) Sarni
(c) Chandrapur
(d) Neyveli
Ans: c
The percentage O2 by Weight in atmospheric air is
(a) 18%
(b) 23%
(c) 77%
(d) 79%
Ans: b
The percentage 02 by volume in atmosphere air is
(a) 21%
(b) 23%
(c) 77%
(d) 79%
Ans: a
The proper indication of incomplete combustion is
(a) high CO content in flue gases at exit
(b) high CO2 content in flue gases at exit
(c) high temperature of flue gases
(d) the smoking exhaust from chimney
Ans: a
The main source of production of biogas is
(a) human waste
(b) wet cow dung
(c) wet livestock waste
(d) all above
Ans: d
India’s first nuclear power plant was installed at
(a) Tarapore
(b) Kota
(c) Kalpakkam
(d) none of the above
Ans: a
In fuel cell, the ______ energy is converted into electrical energy.
(a) mechanical
(b) chemical
(c) heat
(d) sound
Ans: b
Solar thermal power generation can be achieved by
(a) using focusing collector or heliostates
(b) using flat plate collectors
(c) using a solar pond
(d) any of the above system
Ans: d

Economics of Power Generation

Load factor of a power station is defined as
(a) maximum demand/average load
(b) average load x maximum demand
(c) average load/maximum demand
(d) (average load x maximum demand)172
Ans: c
Load factor of a power station is generally
(a) equal to unity
(b) less than unity
(c) more than unity
(d) equal to zero Diversity factor is always
Ans: b
The load factor of domestic load is usually
(a) 10 to 15%
(b) 30 to 40%
(c) 50 to 60%
(d) 60 to 70%
Ans: a
Annual depreciation cost is calculated by
(a) sinkingfund method
(b) straight line method
(c) both (a) and (b)
(d) none of the above
Ans: c
Depreciation charges are high in case of
(a) thermal plant
(b) diesel plant
(c) hydroelectric plant
Ans: a
Demand factor is defined as
(a) average load/maximum load
(b) maximum demand/connected load
(c) connected load/maximum demand
(d) average load x maximum load
Ans: b
High load factor indicates
(a) cost of generation per unit power is increased
(b) total plant capacity is utilised for most of the time
(c) total plant capacity is not properly utilised for most of the time
(d) none of the above
Ans: b
A load curve indicates
(a) average power used during the period
(b) average kWh (kW) energy consumption during the period
(c) either of the above
(d) none of the above
Ans: b
Approximate estimation of power demand can be made by
(a) load survey method
(b) statistical methods
(c) mathematical method
(d) economic parameters
(e) all of the above
Ans: e
Annual depreciation as per straight line method, is calculated by
(a) the capital cost divided by number of year of life
(b) the capital cost minus the salvage value, is divided by the number of years of life
(c) increasing a uniform sum of money per annum at stipulated rate of interest
(d) none of the above
Ans: b
A consumer has to pay lesser fixed charges in
(a) flat rate tariff
(b) two part tariff
(c) maximum demand tariff
(d) any of the above
Ans: c
In two part tariff, variation in load factor will affect
(a) fixed charges
(b) operating or running charges
(c) both (a) and (b)
(d) either (a) or (b)
Ans: b
In Hopknison demand rate or two parttariff the demand rate or fixed charges are
(a) dependent upon the energy consumed
(b) dependent upon the maximum demand of the consumer
(c) both (a) and (b)
(d) neither (a) nor (b)
Ans: b
Which plant can never have 100 percent load factor ?
(a) Peak load plant
(b) Base load plant
(c) Nuclear power plant
(d) Hydro electric plant
Ans: a
The area under a load curve gives
(a) average demand
(b) energy consumed
(c) maximum demand
(d) none of the above
Ans: b
Different generating stations use following prime movers
(a) diesel engine
(b) hydraulic turbine
(c) gas turbine
(d) steam turbine
(e) any of the above
Ans: e
Diversity factor has direct effect on the
(a) fixed cost of unit generated
(b) running cost of unit generated
(c) both (a) and (b)
(d) neither (a) nor (b)
Ans: a
Following power plant has instant starting
(a) nuclear power plant
(b) hydro power plant
(c) diesel power plant
(d) both (b) and (c)
(e) none of the above
Ans: d
Which of the following generating station has minimum ruiyiing cost ?
(a) Nuclear
(b) Hydro
(c) Thermal
(d) Diesel
Ans: b
Power plant having maximum demand more than the installed rated capacity will have utilisation factor
(a) equal to unity
(b) less than unity
(c) more than unity
(d) none of the above
Ans: c
Load curve is useful in deciding the
(a) operating schedule of generating units
(b) sizes of generating units
(c) total installed capacity of the plant
(d) all of the above
Ans: d
Load curve of a power plant has always
(a) zero slope
(b) positive slope
(c) negative slope
(d) any combination of (a), (b) and (c)
Ans: e
Annual operating expenditure of a power plant consists of
(a) fixed charges
(b) semi-fixed charges
(c) running charges
(d) all of the above
Ans: d
Maximum demand on a power plant is
(a) the greatest of all “short time interval averaged” demand during a period
(b) instantaneous maximum value of kVA supplied during a period
(e) both (a) or (b)
(d) none of the above
Ans: a
Annual instalment towards depreciation reduces as rate of interest increases with
(a) sinking fund depreciation
(b) straight line depreciation
(c) reducing balances depreciation
(d) none of the above
Ans: a
Annual depreciation of the plant it proportional to the earning capacity of the plant vide
(a) sinking fund depreciation
(b) straight line depreciation
(c) reducing balances depreciation
(d) none of the above
Ans: c
For high value of diversity factor, a power station of given installed capacity will be in a position to supply
(a) less number of consumers
(b) more number of consumers
(c) neither (a) nor (b)
(d) either (a) or (b)
Ans: b
Salvage value of the plant is always
(a) positive
(b) negative
(c) zero
(d) any of the above
Ans: d
Load curve helps in deciding
(a) total installed capacity of the plant
(b) sizes of the generating units
(c) operating schedule of generating units
(d) all of the above
Ans: d

30 can generate power at unpredictable or uncontrolled times,
(a) Solar power plant
(b) Tidal power plant
(c) Wind power plant
(d) Any of the above
Ans: d

Direct conversion of heat into electric power is possible through
(a) fuel cell
(b) batteries
(c) thermionic converter
(d) all of the above
Ans: c
A low utilization factor for a plant indicates that
(a) plant is used for stand by purpose only
(b) plant is under maintenance
(c) plant is used for base load only
(d) plant is used for peak load as well as base load
Ans: a
Which of the following is not a source of power ?
(a) Thermocouple
(b) Photovoltaic cell
(c) Solar cell
(d) Photoelectric cell
Ans: a
Which of the following should be used for extinguishing electrical fires ?
(a) Water
(b) Carbon tetrachloride fire extinguisher
(c) Foam type fire extinguisher
(d) CO2 fire extinguisher
Ans: b
Low power factor is usually not due to
(a) arc lamps
(b) induction motors
(c) fluorescent tubes
(d) incandescent lamp
Ans: d
Ships are generally powered by
(a) nuclear power plants
(b) hydraulic turbines
(e) diesel engines
(d) steam accumulators
(e) none of the above
Ans: c
Direct conversion of heat into electrical energy is possible through
(a) fuel cells
(b) solar cells
(c) MHD generators
(d) none of the above
Ans: c
Which of the following place is not associated with nuclear power plants in India ?
(a) Narora
(b) Tarapur
(c) Kota
(d) Benglore
Ans: d
During load shedding
(a) system power factor is changed
(b) some loads are switched off
(c) system voltage is reduced
(d) system frequency is reduced Efficiency is the secondary consideration in
Ans: b
which of the following plants ?
(a) Base load plants
(b) Peak load plants
(c) Both (a) and (b)
(d) none of the above
Ans: b
Air will not be the working substance in which of the following ?
(a) Closed cycle gas turbine
(b) Open cycle gas turbine
(c) Diesel engine
(d) Petrol engine
Ans: a
A nuclear power plant is invariably used as a
(a) peak load plant
(b) base load plant
(c) stand-by plant
(d) spinning reserve plant
(e) any of the above
Ans: b
power plant is expected to have the longest life.
(a) Steam
(b) Diesel
(c) Hydroelectric
(d) Any of the above
Ans: c
power plant cannot have single unit of 100 MW.
(a) Hydroelectric
(b) Nuclear
(c) Steam
(d) Diesel
(e) Any of the above
Ans: d
Which of the following, in a thermal power plant, is not a fixed cost ?
(a) Fuel cost
(b) Interest on capital
(c) Depreciation
(d) Insurance charges
Ans: a
_______ will offer the least load.
(a) Vacuum cleaner
(b) Television
(c) Hair dryer
(d) Electric shaver
Ans: d
In ______ fuel transportation cost is least.
(a) nuclear power plants
(b) diesel generating plants
(c) steam power stations
Ans: a
Which of the following equipment provides fluctuating load ?
(a) Exhaust fan
(b) Lathe machine
(c) Welding transformer
(d) All of the above
Ans: c
The increased load during summer months is due to
(a) increased business activity
(b) increased water supply
(c) increased use of fans and air conditioners
(d) none of the above
Ans: c

50 is the reserved generating capacity available for service under emergency conditions which is not kept in operation but in working order,
(a) Hot reserve
(b) Cold reserve
(c) Spinning reserve
(d) Firm power
Ans: b

Generating capacity connected to the bus bars and ready to take load when switched on is known as
(a) firm power
(b) cold reserve
(c) hot reserve
(d) spinning reserve
Ans: d
offers the highest electric load.
(a) Television set
(b) Toaster
(c) Vacuum cleaner
(d) Washing machine
Ans: b
_______ industry has the least power consumption per tonne of product.
(a) Soap
(b) Sugar
(c) Vegetable oil
(d) Caustic soda
Ans: c
With reference to a power station which of the following is not a fixed cost ?
(a) Fuel cost
(b) Interest on capital
(c) Insurance charges
(d) Depreciation
Ans: a
_______ is invariably used as base load plant.
(a) Diesel engine plant
(b) Nuclear power plant
(c) Gas turbine plant
(d) Pumped storage plant
Ans: b
In a power plant if the maximum demand on the plant is equal to the plant capacity, then
(a) plant reserve capacity will be zero
(b) diversity factor will be unity
(c) load factor will be unity
(d) load factor will be nearly 60%
Ans: a
Incase of ______ fuel transportation is the major problem.
(a) diesel power plants
(b) nuclear power plants
(c) hydro-electric power plants
(d) thermal power plants
Ans: d
Which of the following power plants need the least period for installation ?
(a) Thermal power plant
(b) Diesel power plant
(c) Nuclear power plant
(d) Hydro-electric power plant
Ans: b
For which of the following power plants highly skilled engineers are required for running the plants ?
(a) Nuclear power plants
(b) Gas turbine power plants
(c) Solar power plants
(d) Hydro-electric power plants
Ans: a
In which’of the following power plants the maintenance cost is usually high ?
(a) Nuclear power plant
(b) Hydro-electric power plants
(c) Thermal power plants
(d) Diesel engine power plants
Ans: c
________ is invariably used for peak load
(a) Nuclear power plant
(b) Steam turbine plant
(c) Pumped storage plant
(d) None of the above
Ans: c
Which of the following is not an operating cost ?
(a) Maintenance cost
(b) Fuel cost
(c) Salaries of high officials
(d) Salaries of operating staff
Ans:
Which of the following is the essential requirement of peak load plant ?
(a) It should run at high speed
(b) It should produce high voltage
(c) It should be small in size
(d) It should be capable of starting quickly
Ans: d
Large capacity generators are invariably
(a) water cooled
(b) natural air cooled
(c) forced air cooled
(d) hydrogen cooled
Ans: d
By the use of which of the following power factor can be improved ?
(a) Phase advancers
(b) Synchronous compensators
(c) Static capacitors
(d) Any of the above
Ans: d
An induction motor has relatively high power factor at
(a) rated r.p.m.
(b) no load
(c) 20 percent load
(d) near full load
(e) none of the above
Ans: d
Which of the following is the disadvantage due to low power factor ?
(a) Poor voltage regulation
(b) Increased transmission losses
(c) High cost of equipment for a given load
(d) All of the above
Ans: d
In a distribution system, in order to improve power factor, the synchronous capacitors are installed
(a) at the receiving end
(b) at the sending end
(c) either (a) or (b)
(d) none of the above
Ans: a
Static capacitors are rated in terms of
(a) kW
(b) kWh
(e) kVAR
(d) none of the above
Ans: c
Which of the following is the disadvantage of a synchronous condenser ?
(a) High maintenance cost
(b) Continuous losses in motor
(c) Noise
(d) All of the above
Ans: d
For a consumer the most economical power factor is generally
(a) 0.5 lagging
(b) 0.5 leading
(c) 0.95 lagging
(d) 0.95 leading
Ans: c
A synchronous condenser is virtually which of the following ?
(a) Induction motor
(b) Under excited synchronous motor
(c) Over excited synchronous motor
(d) D.C. generator
(e) None of the above
Ans: c
For a power plant which of the following constitutes running cost ?
(a) Cost of wages
(b) Cost of fuel
(c) Cost of lubricants
(d) All of the above
Ans: d
In an interconnected system, the diversity factor of the whole system
(a) remains unchanged
(b) decreases
(c) increases
(d) none of the above
Ans: c
Generators for peak load plants are usually designed for maximum efficiency at
(a) 25 to 50 percent full load
(b) 50 to 75 percent full load
(c) full load
(d) 25 percent overload
Ans: b
________ will be least affected due to charge in supply voltage frequency.
(a) Electric clock
(b) Mixer grinder
(c) Ceiling fan
(d) Room heater
Ans: d
The connected load of a IVMIM uir consumer is around
(a) 5 kW
(b) 40 kV
(c) 80 kW
(d) 120 kW
Ans: a
Which of the following is not necessarily an advantage of interconnecting various power stations ?
(a) Improved frequency of power supplied
(b) Reduction in total installed capacity
(c) Increased reliability
(d) Economy in operation of plants
Ans: a
A power transformer is usually rated in
(a) kW
(b) kVAR
(c) kWh
(d) kVA
Ans: d
public sector undertaking is associated with erection and sometimes running of thermal power plants
(a) NTPC
(b) SAIL
(c) BEL
(d) BHEL
Ans: a
Most efficient plants are normally used as
(a) peak load plants
(b) base load plants
(c) either (a) or (b)
(d) none of the above
Ans:
For a diesel generating station the useful life is expected to be around
(a) 15 to 20 years
(b) 20 to 50 years
(c) 50 to 75 years
(d) 75 to 100 years
Ans: a
Which of the following is not a method for estimating depreciation charges ?
(a) Sinking fund method
(b) Straight line method
(c) Diminishing value method
(d) Halsey’s 50—50 formula
Ans: d
The expected useful life of an hydroelectric power station is around
(a) 15 years
(b) 30 years
(c) 60 years
(d) 100 years
Ans: d
In a load curve the highest point represents
(a) peak demand
(b) average demand
(c) diversified demand
(d) none of the above
Ans: a
Which of the following source of power is least reliable ?
(a) Solar energy
(b) Geothermal power
(c) Wind power
(d) iMHD
Ans:
In India production and distribution of electrical energy is confined to
(a) private sector
(b) public sector
(c) government sectors
(d) joint sector
(e) none of the above
Ans: b
A pilot exciter is provided on generators for which of the following reasons ?
(a) To excite the poles of main exciter
(b) To provide requisite starting torque to main exciter
(c) To provide requisite starting torque to generator
(d) None of the above
Ans: a
The primary reason for low power factor is supply system is due to installation of
(a) induction motors
(b) synchronous motors
(c) single phase motors
(d) d.c. motors
Ans: a
An over excited synchronous motor on noload is known as
(a) synchronous condenser
(b) generator
(c) induction motor
(d) alternator
Ans: a
Which of the following is an advantage of static capacitor for power factor improvement ?
(a) Little maintenance cost
(b) Ease in installation
(c) Low losses
(d) All of the above
Ans: d
For any type of consumer the ideal tariff is
(a) two part tariff
(b) three part tariff
(c) block rate tariff
(d) any of the above
Ans: b
The efficiency of a plant is of least concern when it is selected as
(a) peak load plant
(b) casual run plant
(c) either (a) or (b)
(d) base load plant
Ans: c
Which of the following plants is almost inevitably used as base load plant ?
(a) Diesel engine plant
(b) Gas turbine plant
(c) Nuclear power plant
(d) Pumped storage plant
Ans: c
Which of the following component, in a steam power plant, needs maximum maintenance attention ?
(a) Steam turbine
(b) Condenser
(c) Water treatment plant
(d) Boiler
Ans: d
For the same cylinder dimensions and speed, which of the following engine will produce least power ?
(a) Supercharged engine
(b) Diesel engine
(c) Petrol engine
(d) All of the above engines will equal power
Ans: c
The least share of power is provided in India, by which of the following power plants ? ‘
(a) Diesel power plants
(b) Thermal power plants
(c) Hydro-electric power plants
(d) Nuclear power plants
Ans: a
Submarines for under water movement, are powered by which of the following ?
(a) Steam accumulators
(b) Air motors
(c) Diesel engines
(d) Batteries
Ans: d
An alternator coupled to a _____ runs at slow speed, as compared to as com¬pared to others.
(a) diesel engine
(6) hydraulic turbine
(c) steam turbine
(d) gas turbine
Ans: b
The effect of electric shock on human body depends on which of the following
(a) current
(b) voltage
(c) duration of contact
(d) all of the above
Ans: d
Which lightening stroke is most dangerous ?
(a) Direct stroke on line conductor
(b) Indirect stroke on conductor
(c) Direct stroke on tower top
(d) Direct stroke on ground wire
Ans: a
Which of the following devices may be used to provide protection against lightening over voltages ?
(a) Horn gaps
(b) Rod gaps
(c) Surge absorbers
(d) All of the above
Ans: d
When the demand of consumers is not met by a power plant, it will resort to which of the following ?
(a) Load shedding
(b) Power factor improvement at the , generators
(c) Penalising high load consumers by increasing the charges for electricity
(d) Efficient plant operation
Ans: a
Load shedding is possible through which of the following ?
(a) Switching of the loads
(b) Frequency reduction
(c) Voltage reduction
(d) Any of the above
Ans: d
In power plants insurance cover is provided for which of the following ?
(a) Unskilled workers only
(b) Skilled workers only
(c) Equipment only
(d) All of the above
Ans: d

107 A company can raise funds through
(a) fixed deposits
(b) shares
(c) bonds
(d) any of the above
Ans: d

Which of the following are not repayable after a stipulated period ?
(a) Shares
(b) Fixed deposits
(c) Cash certificates
(d) Bonds
Ans: a
The knowledge of diversity factor helps in determining
(a) plant capacity
(b) average load
(c) peak load
(d) kWh generated
(e) none of the above
Ans: a
Which of the following is the disadvantage of static capacitor for power factor improvement ?
(a) Easily damaged by high voltage
(b) Cannot be repaired
(c) Short service life
(d) All of the above
Ans: d

Transmission & Distribution Multiple Choice Questions

By which of the following systems electric power may be transmitted ?
(a) Overhead system
(b) Underground system
(c) Both (a) and (b)
(d) None of the above
Ans: c
are the conductors, which connect the consumer’s terminals to the distribution
(a) Distributors
(b) Service mains
(c) Feeders
(d) None of the above
Ans: b
The underground system cannot be operated above
(a) 440 V
(b) 11 kV
(c) 33 kV
(d) 66 kV
Ans: d
Overhead system can be designed for operation up to
(a) 11 kV
(b) 33 kV
(c) 66 kV
(d) 400 kV
Ans: c
If variable part of annual cost on account of interest and depreciation on the capital outlay is equal to the annual cost of electrical energy wasted in the conductors, the total annual cost will be minimum and the corresponding size of conductor will be most economical. This statement is known as
(a) Kelvin’s law
(b) Ohm’s law
(c) Kirchhoffs law
(d) Faraday’s law
(e) none of the above
Ans: a
The wooden poles well impregnated with creosite oil or any preservative compound have life
(a) from 2 to 5 years
(b) 10 to 15 years
(c) 25 to 30 years
(d) 60 to 70 years
Ans: c
Which of the following materials is not used for transmission and distribution of electrical power ?
(a) Copper
(b) Aluminium
(c) Steel
(d) Tungsten
Ans: d
Galvanised steel wire is generally used as
(a) stay wire
(b) earth wire
(c) structural components
(d) all of the above
Ans: d
The usual spans with R.C.C. poles are
(a) 40—50 meters
(b) 60—100 meters
(c) 80—100 meters
(d) 300—500 meters
Ans: c
The corona is considerably affected by which of the following ?
(a) Size of the conductor
(b) Shape of the conductor
(c) Surface condition of the conductor
(d) All of the above
Ans: d
Which of the following are the constants of the transmission lines ?
(a) Resistance
(b) Inductance
(c) Capacitance
(d) All of the above
Ans: d
310 km line is considered as
(a) a long line
(b) a medium line
(c) a short line
(d) any of the above
Ans: a
The phenomenon qf rise in voltage at the receiving end of the open-circuited or lightly loaded line is called the
(a) Seeback effect
(b) Ferranti effect
(c) Raman effect
(d) none of the above
Ans: b
The square root of the ratio of line impedance and shunt admittance is called the
(a) surge impedance of the line
(b) conductance of the line
(c) regulation of the line
(d) none of the above
Ans: a
Which of the following is the demerit of a ‘constant voltage transmission system’ ?
(a) Increase of short-circuit current of the system
(b) Availability of steady voltage at all loads at the line terminals
(c) Possibility of better protection for the line due to possible use of higher terminal reactants
(d) Improvement of power factor at times of moderate and heavy loads
(e) Possibility of carrying increased power for a given conductor size in case of long-distance heavy power transmission
Ans: a
Low voltage cables are meant for use up to
(a)l.lkV
(b)3.3kV
(c)6.6kV
(d)llkV
Ans: e
The operating voltage of high voltage cables is up to
(a)l.lkV
(b)3.3kV
(c)6.6kV
(d)llkV
Ans: d
The operating voltage of supertension cables is up to
(a) 3.3 kV
(b) 6.6 kV
(c) 11 kV
(d) 33 kV
Ans: d
The operating voltage of extra high tension cables is upto
(a) 6.6 kV
(b) 11 kV
(c) 33 kV
(d) 66 kV
(e) 132 kV
Ans: d
Which of the following methods is used for laying of underground cables ?
(a) Direct laying
(b) Draw-in-system
(c) Solid system
(d) All of the above
Ans: d
Which of the following is the source of heat generation in the cables ?
(a) Dielectric losses in cable insulation
(b) losses in the conductor
(c) Losses in the metallic sheathings and armourings
(d) All of the above
Ans:
Due to which of the following reasons the cables should not be operated too hot ?
(a) The oil may loose its viscosity and it may start drawing off from higher levels
(b) Expansion of the oil may cause the sheath to burst
(c) Unequal expansion may create voids in the insulation which will lead to ionization
(d) The thermal instability may rise due to the rapid increase of dielectric losses with temperature
(e) All of the above
Ans: e
Which of the following D.C. distribution system is the simplest and lowest in first cost ?
(a) Radial system
(b) Ring system
(c) Inter-connected system
(d) None of the above
Ans: a
A booster is a
(a) series wound generator
(b) shunt wound generator
(c) synchronous generator
(d) none of the above
Ans: a
Besides a method of trial and error, which of the following methods is employed for solution of network problems in interconnected system ?
(a) Circulating current method
(b) Thevenin’s theorem
(c) Superposition of currents
(d) Direct application of Kirehhoffs laws
(e) All of the above
Ans: e
Which of the following faults is most likely to occur in cables ?
(a) Cross or short-circuit fault
(b) Open circuit fault
(c) Breakdown of cable insulation
(d) All of the above
Ans:
The cause of damage to the lead sheath of a cable is
(a) crystallisation of the lead through vibration
(b) chemical action on the lead when buried in the earth
(c) mechanical damage
(d) all of the above
Ans:
The voltage of the single phase supply to residential consumers is
(a) 110 V
(b) 210 V
(c) 230 V
(d) 400 V
Ans: c
Most of the high voltage transmission lines in India are
(a) underground
(b) overhead
(c) either of the above
(d) none of the above
Ans: b
The distributors for residential areas are
(a) single phase
(b) three-phase three wire
(c) three-phase four wire
(d) none of the above
Ans: c
The conductors of the overhead lines are
(a) solid
(b) stranded
(c) both solid and stranded
(d) none of the above
Ans:
High voltage transmission lines use
(a) suspension insulators
(b) pin insulators
(c) both (a) and (b)
(d) none of the above
Ans: a
Multicore cables generally use
(a) square conductors
(b) circular conductors
(c) rectangular conductors
(d) sector-shaped conductors
(e) none of the above
Ans: d
Distribution lines in India generally use
(a) wooden poles
(b) R.C.C. poles
(c) steel towers
(d) none of the above
Ans: b
The material commonly used for insulation in high voltage cables is
(a) lead
(b) paper
(c) rubber
(d) none of the above
Ans: b
The loads on distributors systems are generally
(a) balanced
(b) unbalanced
(c) either of the above
(d) none of the above
Ans: b
The power factor of industrial loads is generally
(a) unity
(b) lagging
(c) leading
(d) zero
Ans: b
Overhead lines generally use
(a) copper conductors
(b) all aluminium conductors
(c) A.C.S.R. conductors
(d) none of these
Ans: c
In transmission lines the cross-arms are made of
(a) copper
(b) wood
(c) R.C.C.
(d) steel
Ans: d
The material generally used for armour of high voltage cables is
(a) aluminium
(b) steel
(c) brass
(d) copper
Ans: b
Transmission line insulators are made of
(a) glass
(b) porcelain
(c) iron
(d) P.V.C.
Ans:
The material commonly used for sheaths of underground cables is
(a) lead
(b) rubber
(c) copper
(d) iron
Ans: a
The minimum clearance between the ground and a 220 kV line is about
(a) 4.3 m
(b) 5.5 m
(c) 7.0 m
(d) 10.5 m
Ans: c
The spacing between phase conductors of a 220 kV line is approximately equal to
(a) 2 m
(b) 3.5 m
(c) 6 m
(d) 8.5 m
Ans: c
Large industrial consumers are supplied electrical energy at
(a) 400 V
(b) 11 kV
(c) 66 kV
(d) 400 kV
Ans: c
In a D.C. 3-wire distribution system, balancer fields are cross-connected in order to
(a) boost the generated voltage
(b) balance loads on both sides of the neutral
(c) make both machine^ run as unloaded motors
(d) equalize voltages on the positive and negative outers
Ans:
In a D.C. 3-wire distributor using balancers and having unequal loads on the two sides
(a) both balancers run as generators
(b) both balancers run as motors
(c) balancer connected to lightly- loaded side runs as a motor
(d) balancer connected to heavily- loaded side runs as a motor
Ans:
Transmitted power remaining the same, if supply voltage of a D.C. 2-wire feeder is increased 100 percent, saving in copper is
(a) 25 percent
(b) 50 percent
(c) 75 percent
(d) 100 percent
Ans: b
A uniformly-loaded D.C. distributor is fed at both ends with equal voltages. As compared to a similar distributor fed at one end only, the drop at the middle point is
(a) one-fourth
(b) one-third
(c) one-half
(d) twice
(e) none of the above
Ans: a
As compared to a 2-wire D.C. distributor, a 3-wire distributor with same maximum voltage to earth uses only
(a) 31.25 percent of copper
(b) 33.3 percent of copper
(c) 66.7 percent of copper
(d) 125 percent of copper
Ans: a
Which of the following is usually not the generating voltage ?
(a) 6.6 kV
(b) 8.8 kV
(c) 11 kV
(d) 13.2 kV
Ans: b
For an overhead line, the surge impedance is taken as
(a) 20-30 ohms
(b) 70—80 ohms
(c) 100—200 ohms
(d) 500—1000 ohms
(e) none of the above
Ans: c
The presence of ozone due to corona is harmful because it
(a) reduces power factor
(b) corrodes the material
(c) gives odour
(d) transfer energy to the ground
(e) none of the above
Ans: b
A feeder, in a transmission system, feeds power to
(a) distributors
(b) generating stations
(c) service mains
(d) all of the above
Ans: a
The power transmitted will be maximum when
(a) corona losses are minimum
(b) reactance is high
(c) sending end voltage is more
(d) receiving end voltage is more
Ans: c
A 3-phase 4 wire system is commonly used on
(a) primary transmission
(b) secondary transmission
(c) primary distribution
(d) secondary distribution
Ans: d
Which of the following materials is used for overhead transmission lines ?
(a) Steel cored aluminium
(b) Galvanised steel
(c) Cadmium copper
(d) Any of the above
Ans: d
Which of the following is not a constituent for making porcelain insulators ?
(a) Quartz
(b) Kaolin
(c) Felspar
(d) Silica
Ans: d
There is a greater possibility of occurence of corona during
(a) dry weather
(b) winter
(c) summer heat
(d) humid weather
(e) none of the above
Ans: d
Which of the following relays is used on long transmission lines ?
(a) Impedance relay
(b) Mho’s relay
(c) Reactance relay
(d) None of the above
Ans: b
The steel used in steel cored conductors is usually
(a) alloy steel
(b) stainless steel
(c) mild steel
(d) high speed steel
(e) all of the above
Ans: c
Which of the following distribution systems is more reliable ?
(a) Radial system
(b) Tree system
(c) Ring main system
(d) All are equally reliable
Ans: c
Which of the following characteristics should the line supports for transmission lines possess ?
(a) Low cost
(b) High mechanical strength
(c) Longer life
(d) All of the above
Ans: d
Transmission voltage of ll kV is normally used for distances upto
(a) 20—25 km
(b) 40—50 km
(c) 60—70 km
(d) 80—100 km
Ans: a
Which of the following regulations is considered best?
(a) 50%
(b) 20%
(c) 10%
(d) 2%
Ans: d
Skin effect is proportional to
(a) (conductor diameter)
(b) (conductor diameter)
(c) (conductor diameter)
(d) (conductor diameter)
(e) none of the above
Ans: c
A conductor, due to sag between two supports, takes the form of
(a) semi-circle
(b) triangle
(c) ellipse
(d) catenary
Ans: d
In AC.S.R. conductors, the insulation between aluminium and steel conductors is
(a) insulin
(b) bitumen
(c) varnish
(d) no insulation is required
Ans: d
Which of the following bus-bar schemes has the lowest cost ?
(a) Ring bus-bar scheme
(b) Single bus-bar scheme
(c) Breaker and a half scheme
(d) Main and transfer scheme
Ans: b
Owing to skin effect
(a) current flows through the half cross-section of the conductor
(b) portion of the conductor near the surface carries more current and core of the conductor carries less current
(c) portion of the conductor near the surface carries less current and core of the conductor carries more cur¬rent
(d) any of the above
(e) none of the above
Ans: b
By which of the following methods string efficiency can be improved ?
(a) Using a guard ring
(b) Grading the insulator
(c) Using long cross arm
(d) Any of the above
(e) None of the above
Ans: d
In aluminium conductors, steel core is provided to
(a) compensate for skin effect
(b) neutralise proximity effect
(c) reduce line inductance
(d) increase the tensile strength
Ans: d
By which of the following a bus-bar is rated ?
(a) Current only
(b) Current and voltage
(c) Current, voltage and frequency
(d) Current, voltage, frequency and short time current
Ans: d
A circuit is disconnected by isolators when
(a) line is energized
(b) there is no current in the line
(c) line is on full load
(d) circuit breaker is not open
Ans: b
For which of the following equipment current rating is not necessary ?
(a) Circuit breakers
(b) Isolators
(c) Load break switch
(d) Circuit breakers and load break switches
Ans: b
In a substation the following equipment is not installed
(a) exciters
(b) series capacitors
(c) shunt reactors
(d) voltatre transformers
Ans: a
jCorona usually occurs when the electrostatic stress in air around the conductor exceeds
(a) 6.6 kV (r.m.s. value)/cm
(b) 11 kV (r.m.s. value)/cm
(c) 22 kV (maximum value)/cm
(d) 30 kV (maximum value)/cm
Ans: d
The voltage drop, for constant voltage transmission is compensated by installing
(a) inductors
(b) capacitors
(c) synchronous motors
(d) all of above
(e) none of the above
Ans: c
The use of strain type insulators is made where the conductors are
(a) dead ended
(b) at intermediate anchor towers
(c) any of the above
(d) none of the above
Ans: c
The current drawn by the line due to corona losses is
(a) non-sinusoidal
(b) sinusoidal
(c) triangular
(d) square
Ans: a
Pin type insulators are generally not used for voltages beyond
(a) 1 kV
(b) 11 kV
(c) 22 kV
(d) 33 kV
Ans: d
Aluminium has a specific gravity of
(a) 1.5
(b) 2.7
(c) 4.2
(d) 7.8
Ans: b
For transmission of power over a distance of 200 km, the transmission voltage should be
(a) 132 kV
(b) 66 kV
(c) 33 kV
(d) 11 kV
Ans: a
For aluminium, as compared to copper, all the following factors have higher values except
(a) specific volume
(6) electrical conductivity
(c) co-efficient of linear expansion
(d) resistance per unit length for same cross-section
Ans: b
Which of the following equipment, for regulating the voltage in distribution feeder, will be most economical ?
(a) Static condenser
(b) Synchronous condenser
(c) Tap changing transformer
(d) Booster transformer
Ans: d
In a tap changing transformer, the tappings are provided on
(a) primary winding
(b) secondary winding
(c) high voltage winding
(d) any of the above
Ans: c
Constant voltage transmission entails the following disadvantage
(a) large conductor area is required for same power transmission
(b) short-circuit current of the system is increased
(c) either of the above
(d) none of the above
Ans: b
On which of the following factors skin effect depends ?
(a) Frequency of the current
(b) Size of the conductor
(c) Resistivity of the conductor material
(d) All of the above
Ans: d
The effect of corona can be detected by
(a) presence of ozone detected by odour
(b) hissing sound
(c) faint luminous glow of bluish colour
(d) all of the above
Ans: d
For transmission of power over a distance of 500 km, the transmission voltage should be in the range
(a) 150 to 220 kV
(b) 100 to 120 kV
(c) 60 to 100 kV
(d) 20 to 50 kV
Ans: a
In the analysis of which of the following lines shunt capacitance is neglected ?
(a) Short transmission lines
(b) Medium transmission lines
(c) Long transmission lines
(d) Medium as well as long transmission lines
Ans: a
When the interconnector between two stations has large reactance
(a) the transfer of power will take place with voltage fluctuation and noise
(b) the transfer of power will take place with least loss
(c) the stations will fall out of step be¬cause of large angular displacement between the stations
(d) none of the above
Ans: c
The frequency of voltage generated, in case of generators, can be increased by
(a) using reactors
(b) increasing the load
(c) adjusting the governor
(d) reducing the terminal voltage
(e) none of the above
Ans: c
When an alternator connected to the bus-bar is shut down the bus-bar voltage will
(a) fall
(b) rise
(c) remain unchanged
(d) none of the above
Ans: c
The angular displacement between two interconnected stations is mainly due to
(a) armature reactance of both alternators
(b) reactance of the interconnector
(c) synchronous reactance of both the alternators
(d) all of the above
Ans: a
Electro-mechanical voltage regulators are generally used in
(a) reactors
(b) generators
(c) transformers
(d) all of the above
Ans: b
Series capacitors on transmission lines are of little use when the load VAR requirement is
(a) large
(b) small
(b) fluctuating
(d) any of the above
Ans: b
The voltage regulation in magnetic amplifier type voltage regulator is effected by
(a) electromagnetic induction
(b) varying the resistance
(c) varying the reactance
(d) variable transformer
Ans: c
When a conductor carries more current on the surface as compared to core, it is due to
(a) permeability variation
(b) corona
(c) skin effect
(d) unsymmetrical fault
(e) none of the above
Ans: c
The following system is not generally used
(a) 1-phase 3 wire
(b) 1-phase 4 wire
(c) 3-phase 3 wire
(d) 3-phase 4 wire
Ans: a
The skin effect of a conductor will reduce as the
(a) resistivity of conductor material increases
(b) permeability of conductor material increases
(c) diameter increases
(d) frequency increases
Ans: a
When a live conductor of public electric supply breaks down and touches the earth which of the following will happen ?
(a) Current will flow to earth
(b) Supply voltage will drop
(c) Supply voltage will increase
(d) No current will flow in the conductor
(e) None of the above
Ans: a

Switchgear & Protection

The main function of a fuse is to
(a) protect the line
(b) open the circuit
(c) protect the appliance
(d) prevent excessive currents
(e) none of the above
Ans: d
On which of the following routine tests are conducted ?
(a) Oil circuit breakers
(b) Air blast circuit breakers
(c) Minimum oil circuit breakers
(d) All of the above
Ans: d
SF6 gas
(a) is yellow in colour
(b) is lighter than air
(c) is nontoxic
(d) has pungent small
(e) none of the above
Ans: c
The arcing contacts in a circuit breaker are made of
(a) copper tungsten alloy
(b) porcelain
(c) electrolytic copper
(d) aluminium alloy
Ans: a
Which of the following medium is employed for extinction of arc in air circuit breaker ?
(a) Water
(b) Oil
(c) Air
(d) SF6
Ans: c
With which of the following, a circuit breaker must be equipped for remote operation ?
(a) Inverse time trip
(b) Time-delay trip
(c) Shunt trip
(d) None of the above
(e) All of the above
Ans: c
Fault diverters are basically
(a) fuses
(b) relays
(c) fast switches
(d) circuit breakers
Ans: c
A thermal protection switch can protect against
(a) short-circuit
(b) temperature
(c) overload
(d) over voltage
Ans: c
Arc in a circuit behaves as
(a) a capackive reactance
(b) an inductive reactance
(c) a resistance increasing with voltage rise across the arc
(d) a resistance decreasing with voltage rise across the arc
Ans: d
Thermal circuit breaker has
(a) delayed trip action
(b) instantaneous trip action
(c) both of the above
(d) none of the above
Ans: a
Relays can be designed to respond to changes in
(a) resistance, reactance or impedance
(b) voltage and current
(c) light intensity
(d) temperature
(e) all above
Ans: e
Overload relays are of…… type.
(a) induction
(b) solid state
(c) thermal
(d) electromagnetic
(e) all above
Ans: e
Thermal overload relays are used to protect the motor against over current due to
(a) short-circuits
(b) heavy loads
(c) grounds
(d) all of the above
Ans: b
Magnetic circuit breaker has ______ trip action.
(a) delayed
(b) instantaneous
(c) both of the above
(d) none of the above
Ans: b
D.C. shunt relays are made of
(a) few turns of thin wire
(b) few turns of thick wire
(c) many turns of thin wire
(d) many turns of thick wire
Ans: c
The relay operating speed depends upon
(a) the spring tension
(b) the rate of flux built up
(c) armature core air gap
(d) all of the above
Ans: d
In order that current should flow without causing excessive heating or voltage drop, the relay contacts should
(a) have low contact resistance
(b) be clean and smooth
(c) be of sufficient size and proper shape
(d) have all above properties
Ans: d
Circuit breakers usually operate under
(a) transient state of short-circuit current
(b) sub-transient state of short-circuit current
(c) steady state of short-circuit current
(d) after D.C. component has ceased
Ans: a
Circuit breakers are essentially
(a) current carrying contacts called electrodes
(b) arc extinguishers
(c) circuits to break the system
(d) transformers to isolate the two systems
(e) any of the above
Ans: a

The current zero interruption, in oil and air blast circuit breakers, is achieved by
(a) lengthening of the gap
(b) cooling and blast effect
(c) both (a) and (b)
(d) deionizing the oil with forced air
(e) none of the above
Ans: c

Air blast circuit breaker is used for
(a) over currents
(b) short duty
(c) intermittant duty
(d) repeated duty
Ans: d
An efficient and a well designed protective relaying should have
(a) good selectivity and reliability
(b) economy and simplicity
(c) high speed and selectivity
(d) all of the above
Ans: d
Burden of a protective relay is the power
(a) required to operate the circuit breaker
(b) absorbed by the circuit of relay
(c) developed by the relay circuit
(d) none of the above
Ans: b
Directional relays are based on flow of
(a) power
(b) current
(c) voltage wave
(d) all of the above
Ans: a
A differential relay measures the vector difference between
(a) two currents
(b) two voltages
(c) two or more similar electrical quantities
(d) none of the above
Ans: c
A transmission line is protected by
(a) inrush protection
(b) distance protection
(c) time graded and current graded over current protection
(d) both (b) and (c)
(e) none of the above
Ans: d
Large internal faults are protected by
(a) merz price percentage differential protection
(b) mho and ohm relays
(c) horn gaps and temperature relays
(d) earth fault and positive sequence relays
Ans: a
When a transmission line is energized, the wave that propagates on it is
(a) current wave only
(b) voltage wave only
(c) both (a) and (b)
(d) power factor wave only
Ans: c
Protective relays are devices that detect abnormal conditions in electrical circuits by measuring
(a) current during abnormal condition
(b) voltage during abnormal condition
(c) constantly the electrical quantities which differ during normal and abnormal conditions
(d) none of the above
Ans: c
The voltage appearing across the contacts after opening of the circuit breaker is called______voltage.
(a) recovery
(b) surge
(c) operating
(d) arc
(e) none of the above
Ans: a
Ionization in circuit breaker is facilitated by
(a) high temperature
(b) increase of mean free path
(c) increasing field strength
(d) all of the above
Ans: d
In a circuit breaker the basic problem is to
(a) maintain the arc
(b) extinguish the arc
(c) transmit large power
(d) emit the ionizing electrons
Ans: c
Overheating of relay contacts or contact born out is due to
(a) slow making and breaking of load circuit contacts
(b) foreign matter on the contact surface
(c) too low contact pressure
(d) all of the above
Ans: d
Interruption of large currents by relay requires
(a) arc suppressing blow out coils
(b) wide separation of the opened contacts
(c) high speed opening of contacts
(d) all of the above
Ans: d
Shunt capacitance is neglected while considering
(a) short transmission line
(b) medium transmission line
(c) long transmission line
(d) medium and long transmission lines
Ans: a
The arc voltage produced in A.C. circuit breaker is always
(a) in phase with the arc current
(b) lagging the arc current by 90″
(c) leading the arc current by 90°
(d) none of the above
Ans: a
The time of closing the cycle, in modern circuit breakers is
(a) 0.003 sec
(b) 0.001 sec
(c) 0.01 sec
(d) 0.10 sec
(e) none of the above
Ans: a
Insulation resistance of high voltage circuit breakers is more than
(a) 1 mega ohms
(b) 10 mega ohms
(c) 100 mega ohms
(d) 500 mega ohms
Ans: c
H.R.C. fuses provide best protection against
(a) overload
(b) reverse current
(c) open-circuits
(d) short-circuits
Ans: d
The ground wire should not be smaller than No ______ copper.
(a) 2
(b) 4
(c) 6
(d) 10
Ans: d
The delay fuses are used for the protection of ________ .
(a) motors
(b) power outlet circuits
(c) fluorescent lamps
(d) light circuits
Ans: a
Which of the following is the least expensive protection for overcurrent is low voltage system ?
(a) Rewireable fuse
(b) Isolator
(c) Oil circuit breaker
(d) Air break circuit breaker
(e) None of the above
Ans: a
Resistance grounding is used for voltage between
(a) 33kVto66kV
(b) HkVto33kV
(c) 3.3kVandllkV
(d) none of the above
Ans: c
The contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to
(a) lubricate the contacts
(b) insulate the contacts from switch body
(c) extinguish the arc
(d) all of the above
(e) none of the above
Ans: c
In Railway applications ______ circuit breaker is used.
(a) SFe
(b) bulk oil
(c) minimum oil
(d) air break
Ans:
To protect most of the electrical equipment handling low power, the types of relays used are
(a) thermocouple
(b) electronic and bimetallic
(c) both (a) and (b)
(d) none of the above
Ans: c
Wave trap is used to trap waves of
(a) power frequencies
(b) higher frequencies entering generator or transformer units
(c) either of the above
(d) none of the above
Ans: b
Ungrounded neutral transmission system is not recommended because of system
(a) insulation being overstressed due to over voltages
(b) insulation overstress may lead to failure and subsequent phase to phase faults
(c) being inadequately protected against ground fault
(d) all of the above
Ans: d
The reflection co-efficient at the open circuited end of a transmission line.
(a) zero
(b) infinity
(c) unity
(d) none of the above
Ans: c
For the protection of power station buildings against direct strokes the requirements are
(a) interception
(b) interception and conduction
(c) interception, conduction and dissipation
(d) interception, conduction, dissipation and reflection
(e) none of the above
Ans: c
The line insulation is the insulation level of the station equipment.
(a) less than
(b) same as
(c) more than
(d) proportional to
(e) not directly related with
Ans: e
The interaction between a transmission line and communication line is minimized by
(a) transposing transmission as well as communication lines
(b) increasing the height of the trans-mission line tower
(c) increasing the distance between the two lines
(d) all of the above
Ans: d
When a wave propagates on a transmission line, it suffers reflection several times at
(a) tapping
(b) load end
(c) sending end
(d) sending and other end
(e) all of the above
Ans: d
Which of the following statements is incorrect?
(a) Station batteries are used to operate relay only
(b) The lightning arresters are basically surge diverters
(c) An impedance relay has maximum fault current when fault occurs near the relay
(d) A high speed relay has an operation of 1 to 2 cycles
Ans: a
Discrimination between main and back up protection is provided by the use of relays which are
(a) fact
(b) sensitive
(c) slow
(d) none of the above
Ans: c
Induction cup relay is operated due to changes in
(a) current
(b) voltage
(c) impedance
(d) all of the above
Ans: d
A.C. network analyser is used to solve problems of
(a) load flow
(b) load flow and short-circuit
(c) load flow and stability
(d) load flow, short-circuit and stability
(e) none of the above
Ans: d
Which of the following statements is incorrect ?
(a) Lightning arrestors are used before the switchgear
(b) Shunt reactors are used as compensation reactors
(c) The peak short current is (1.8 xV2) times the A.C. component
(d) The MVA at fault is equal to base MVA divided by per unit equivalent fault reactance
Ans: a
Short-circuit currents are due to
(a) single phase to ground faults
(b) phase to phase faults
(c) two phase to ground faults
(d) three phase faults
(e) any of these
Ans: e
To reduce short circuit fault currents are used.
(a) reactors
(b) resistors
(c) capacitors
(d) none of the above
Ans: a
Bus coupler is very essential in arrangement
(a) single bus
(b) double bus, double breaker
(c) main and transfer bus
(d) all of the above
Ans: c
For cost and safety, the outdoor substations are installed for voltages above
(a) 11 kV
(b) 33 kV
(c) 60kV
(d) 110kV
Ans: b
The short circuit in any winding of the transformer is the result of
(a) mechanical vibration
(b) insulation failure
(c) loose connection
(d) impulse voltage
Ans: d

64 relays are used for phase faults on long line.
(a) Impedance
(b) Reactance
(c) Either of the above
(d) None of the above
Ans: a

For which of the following protection from negative sequence currents is provided ?
(a) Generators
(b) Motors
(c) Transmission line
(d) Transformers
Ans: a

66 relay is preferred for phase fault on short transmission line.
(a) Induction type
(b) Reactance
(c) Impedance
(d) None of the above
Ans: b

Distance relays are generally
(a) split-phase relays
(b) reactance relays
(c) impedance relays
(d) none of the above
Ans: d
For which of the following ratings of the transformer differential protection is recommended ?
(a) above 30 kVA.
(b) equal to and above 5 MVA
(c) equal to and above 25 MVA
(d) none of the above
Ans: b
A _______ is used to measure the stator % winding temperature of the generator.
(a) thermocouple
(b) pyrometer
(c) resistance thermometer
(d) thermometer
Ans: c
The under voltage relay can be used for
(a) generators
(b) busbars
(c) transformers
(d) motors
(e) all of the above
Ans: e
The relay with inverse time characteristic will operate within
(a) 1.5 sec
(b) 5 to 10 sec
(c) 5 to 20 sec
(d) 20 to 30 sec
(e) none of the above
Ans: b
The single phasing relays are used for the protection of
(a) single phase motors only
(b) two phase motors only
(c) two single phase motors running in parallel
(d) three phase motors
Ans: d
Which of the following devices will receive voltage surge first travelling on the transmission line ?
(a) Lightning arresters
(b) Relays
(c) Step-down transformer
(d) Switchgear
Ans: a
Which of the following parameter can be neglected for a short line ?
(a) Inductance
(b) Capacitance
(c) Resistance
(d) Reactance
Ans: b
Series reactors should have
(a) low resistance
(b) high resistance
(c) low impedance
(d) high impedance
Ans: a
Which of the following circuit breakers has high reliability and minimum maintenance ?
(a) Air blast circuit breakers
(b) Circuit breaker with SF6 gas
(c) Vacuum circuit breakers
(d) Oil circuit breakers
Ans: b
Arc in a circuit breaker is interrupted at
(a) zero current
(b) maximum current
(c) minimum voltage
(d) maximum voltage
Ans: a

78 transmission line has reflection coefficient as one.
(a) Open circuit
(b) Short-circuit
(e) Long
(d) None of the above
Ans: a

What will be the reflection co-efficient of the wave of load connected to transmission line if surge impedance of the line is equal to load ?
(a) Zero
(b) Unity
(c) Infinity
(d) None of the above
Ans: a
The inverse definite mean time relays are used for over current and earth fault protection of transformer against
(a) heavy loads
(b) internal short-circuits
(c) external short-circuits
(d) all of the above
Ans: b
Over voltage protection is recommended for
(a) hydro-electric generators
(b) steam turbine generators
(c) gas turbine generators
(d) all of the above
(e) none of the above
Ans: d
Air blast circuit breakers for 400 kV power system are designed to operate in
(a) 100 microsecond
(b) 50 millisecond
(c) 0.5 sec
(d) 0.1 sec
Ans: b
Overfluxing protection is recommended for
(a) distribution transformer
(b) generator transformer of the power plant
(c) auto-transformer of the power plant
(d) station transformer of the power plant
Ans: b
Series capacitors are used to
(a) compensate for line inductive reactance
(b) compensate for line capacitive reactance
(c) improve line voltage
(d) none of the above
Ans: a
Admittance relay is _______ relay.
(a) impedance
(b) directional
(c) non-directional
(d) none of the above
Ans: b
The material used for fuse must have
(a) low melting point and high specific resistance
(b) low melting point and -low specific resistance
(c) high melting point and low specific resistance
(d) low melting point and any specific resistance
Ans: a
If the fault occurs near the impedance relay, the VII ratio will be
(a) constant for all distances
(b) lower than that of if fault occurs away from the relay
(c) higher than that of if fault occurs away from the relay
(d) none of the above
Ans: b
The torque produced in induction type relay (shaded pole structure) is
(a) inversely proportional to the current
(b) inversely proportional to the square of the current
(c) proportional to the current
(d) proportional to square of the current
Ans: b
The steady state stability of the power system can be increased by
(a) connecting lines in parallel
(b) connecting lines in series
(e) using machines of high impedance
(d) reducing the excitation of machines
(e) none of the above
Ans: a
The inductive interference between power and communication line can be minimized by
(a) transposition of the power line
(b) transposition of the communication line
(c) both (a) and (b)
(d) increasing the distance between the conductors
Ans: c
The power loss is an important factor for the design of
(a) transmission line
(b) motor
(c) generator
(d) feeder
Ans: a
A fuse is connected
(a) in series with circuit
(b) in parallel with circuit
(c) either in series or in parallel with circuit
(d) none of the above
Ans: a
H.R.C. fuse, as compared to a rewirable fuse, has
(a) no ageing effect
(b) high speed of operation
(c) high rupturing capacity
(d) all of the above
Ans: d
The fuse rating is expressed in terms of
(a) current
(b) voltage
(c) VAR
(d) kVA
Ans: a
The fuse blows off by
(a) burning
(b) arcing
(c) melting
(d) none of the above
Ans: c
On which of the following effects of electric current a fuse operates ?
(a) Photoelectric effect
(b) Electrostatic effect
(c) Heating effect
(d) Magnetic effect
Ans: c
An isolator is installed
(a) to operate the relay of circuit breaker
(b) as a substitute for circuit breaker
(c) always independent of the position of circuit breaker
(d) generally on both sides of a circuit breaker
Ans: d
A fuse in a motor circuit provides protection against
(a) overload
(b) short-circuit and overload
(c) open circuit, short-circuit and overload
(d) none of the above
Ans: b
Protection by fuses is generally not used beyond
(a) 20 A
(b) 50 A
(c) 100 A
(d) 200 A
Ans: c
A fuse is never inserted in
(a) neutral wire
(b) negative of D.C. circuit
(c) positive of D.C. circuit
(d) phase dine
Ans: a
Oil switches are employed for
(a) low currents circuits
(b) low voltages circuits
(c) high voltages and large currents circuits
(d) all circuits
Ans: c
A switchgear is device used for
(a) interrupting an electrical circuit
(b) switching an electrical circuit 111.
(c) switching and controlling an electrical circuit
(d) switching, controlling and protecting the electrical circuit and equipment
Ans: d
The fuse wire, in D.C. circuits, is inserted in
(a) negative circuit only
(b) positive circuit only
(c) both (a) and (b)
(d) either (a) or (b)
Ans: c
By which of the following methods major portion of the heat generated in a H.R.C. fuse is dissipated ?
(a) Radiation
(b) Convection
(c) Conduction
(d) All of the above
Ans: c
A short-circuit is identified by
(a) no current flow
(b) heavy current flow
(c) voltage drop
(d) voltage rise
Ans: b
The information to the circuit breaker under fault conditions is provided by
(a) relay
(b) rewirable fuse
(c) H.R.C. only
(d) all of the above
Ans: a
To limit short-circuit current in a power system are used.
(a) earth wires
(b) isolators
(c) H.R.C. fuses
(d) reactors
Ans: d
A balanced 3-phase system consists of
(a) zero sequence currents only
(b) positive sequence currents only
(c) negative and zero sequence currents
(d) zero, negative and positive sequence currents
Ans: b
In a single bus-bar system there will be complete shut down when
(a) fault occurs on the bus itself
(b) fault occurs on neutral line
(c) two or more faults occur simultaneously
(d) fault occurs with respect to earthing
Ans: a

Electrical Engineering Materials

The converse of hardness is known as
(a) malleability
(b) toughness
(c) softness
(d) none of the above
Ans: c
On which of the following factors does the resistivity of a material depend ?
(a) Resistance of the conductor
(b) Area of the conductor section
(c) Length of the conductor
(d) All of the above
Ans: d
is a negatively charged particle present in an atom.
(a) Proton
(b) Neutron
(c) Electron
(d) None of the above
Ans: c
The formula ____ determines the number of electrons that can be accommodated in any level.
(a) 2n2
(6) 4n2
(c) 2n3
(d) 4ns
Ans: a
The tiny block formed by the arrangement of a small group of atoms is called the
(a) unit cell
(b) space lattice
(c) either (a) or (b)
(d) none of the above
Ans: a
The co-ordination number of a simple cubic structure is
(a) 2
(b) 4
(c) 6
(d) 8
Ans: c
The covalent bond is formed by
(a) transfer of electrons between atoms
(b) sharing of electrons between atoms
(e) sharing of variable number of electrons by a variable number of atoms
(d) none of the above
Ans: b
A perfect conductor has
(a) zero conductivity
(b) unity conductivity
(c) infinite conductivity
(d) none of the above
Ans: c
The metal having the lowest temperature coefficient of resistance is
(a) gold
(b) copper
(c) aluminium
(d) kanthal
Ans: a
Commonly used conducting materials are
(a) copper
(b) aluminium
(c) both (a) and (b)
(d) copper and silver
(e) platinum and gold
Ans: c
Which of the following materials is preferred for transmitting electrical energy over long distance ?
(a) Copper
(b) Aluminium
(c) Steel reinforced copper
(d) Steel reinforced aluminium
Ans: d
The kinetic energy of a bounded electron is
(a) less than that of unbounded electron
(6) greater than that of unbounded electron
(c) equal to that of unbounded electron
(d) infinite
(e) none of the above
Ans: a
A highly conductive material must have
(a) highest conductivity
(b) lowest temperature co-efficient
(c) good mechanical strength
(d) good corrosion resistance
(e) easy solderable and drawable quality
(f) all of the above
Ans: f
The conductivity of a conductor can be increased by
(a) decreasing its temperature
(b) increasing its temperature
(c) decreasing its vibration
(d) increasing its vibration
Ans: a
Superconductivity is observed for
(a) infrared frequencies
(b) d.c. and low frequency
(c) a.c. and high frequency
(d) frequencies having no effect
(e) none of the above
Ans: b
The superconductivity is due to
(a) the crystal structure having no atomic vibration at 0°K
(b) all electrons interact in the super-conducting state
(c) the electrons jump into nucleus at 0°K
(d) none of the above
Ans: a
The value of critical field below the transition temperature will
(a) increase
(b) decrease
(c) remain unchanged
(d) any of the above
Ans: a
In a superconductor the value of critical density depends upon
(a) magnetic field strength
(b) temperature
(c) either (a) or (b)
(d) both (a) and (b)
Ans: d
Superconductors are becoming popular for use in
(a) generating very strong magnetic field
(b) manufacture of bubble memories
(c) generating electrostatic field
(d) generating regions free from magnetic field
Ans: a
High resistivity materials are used in
(a) precision instruments
(6) heating elements
(c) motor starters
(d) incandescent lamps
(e) all of the above
Ans: e
Mercury as an electric contact material is
(a) a liquid
(b) a metal
(c) a metal liquid
(d) a gas
Ans: c
An H.R.C. fuse is
(a) a ceramic body having metal and caps
(b) a wire of platinum
(c) a heavy cross-section of copper or aluminium
(d) a ceramic tube having carbon rod inside it
Ans: a
Which of the following resistive materials has the lowest temperature co-efficient of resistance ?
(a) Nichrome
(b) Constantan
(c) Kanthal
(d) Molybdenum
Ans: a
The coils of D.C. motor starter are wound with wire of
(a) copper
(b) kanthal
(c) manganin
(d) nichrome
Ans: c
The conductors have transport phenomena of electrons due to
(a) electric field
(b) magnetic field
(c) electromagnetic field
(d) none of the above
Ans: a
The transition temperature of mercury is
(a) 18.0°K
(6) 9.22°K
(c) 4.12°K
(d) 1.14’K
Ans: c
By increasing impurity content in the metal alloy the residual resistivity always
(a) decreases
(b) increases
(c) remains constant
(d) becomes temperature independent
Ans: b
The structure sensitive property of a super conductor is
(a) critical magnetic field
(b) transition temperature
(c) critical current density
(d) none of the above
Ans: c
At transition temperature the value of critical field is
(a) zero
(6) negative real value
(c) positive real value
(d) complex value
Ans: a
Which of the following variety of copper has the best conductivity ?
(a) Induction hardened copper
(b) Hard drawn copper
(c) Pure annealed copper
(d) Copper containing traces of silicon
Ans: c
Constantan contains
(a) silver and tin
(b) copper and tungsten
(c) tungsten and silver
(d) copper and nickel
Ans: d
Which of the following is the poorest conductor of electricity ?
(a) Carbon
(b) Steel
(c) Silver
(d) Aluminium
Ans: a

33 ______ has zero temperature co-efficient of resistance.
(a) Aluminium
(b) Carbon
(c) Porcelain
(d) Manganin
Ans: d

Piezoelectric materials serve as a source of _____ .
(a) resonant waves
(b) musical waves
(c) microwaves
(d) ultrasonic waves
Ans: d
In thermocouples which of the following pairs is commonly used ?
(a) Copper-constantan
(b) Aluminium-tin
(c) Silver-German silver
(d) Iron-steel
Ans: a

36 is viscoelastic.
(a) Cast-iron
(6) Graphite
(c) Rubber
(d) Glass
Ans: c

Carbon electrodes are not used in
(a) GLS lamps
(b) electric arc furnace
(c) dry cells
(d) cinema projectors
Ans: a
Solder is an alloy of
(a) copper and aluminium
(b) tin and lead
(c) nickel, copper and zinc
(d) silver, copper and lead
Ans: b

39 ______ is most commonly used for making magnetic recording tape
(a) Silver nitrate
(b) Ferric oxide
(c) Small particles of iron
(d) Silicon-iron
Ans: b

Overhead telephone wires are made of
(a) aluminium
(b) steel
(c) ACSR conductors
(d) copper
Ans: b
______ is an example of piezoelectric material.
(a) Glass
(b) Quartz
(c) Corrundum
(d) Neoprene
Ans: b
_____ is the main constituent of glass
(a) Fe203
(b) Si02
(c) AI2O3
(d) B2O3
Ans: b
A good electric contact material should have all of the following properties except
(a) high resistivity
(b) high resistance to corrosion
(c) good thermal conductivity
(d) high melting point
Ans: a
Most of the common metals have _____ structure.
(a) linear
(b) hexagonal
(c) orthorhombic
(d) cubic
Ans: d
Which of the following affect greatly the resistivity of electrical conductors ?
(a) Composition
(b) Pressure
(c) Size
(d) Temperature
Ans: a
Thermonic emission occurs in
(a) vacuum tubes
(b) copper conductors
(c) ferrite cores
(d) transistors
Ans: a
_____ is a hard solder.
(a) Tin-lead
(6) Tin-silver-lead
(c) Copper-zinc
(d) None of the above
Ans: c
Addition of 0.3 to 4.5% silicon to iron _____ the electrical resistivity of iron.
(a) increases
(b) decreases
(c) does not change
Ans: a
Super conductivity can be destroyed by
(a) adding impurities
(b) reducing temperatures
(c) application of magnetic field
(d) any of the above
Ans: c
Non-linear resistors
(a) produce harmonic distortion
(b) follows Ohm’s law at low temperatures only
(c) result in non-uniform heating
(d) none of the above
Ans: a
A carbon resistor contains
(a) carbon crystals
(b) solid carbon granules
(c) pulverized coal
(d) finely divided carbon black.
Ans: d
Which of the following materials does not have covalent bonds ?
(a) Organic polymers
(b) Silicon
(c) Metals
Ans: c
In graphite, bonding is
(a) covalent
(b) metallic
(c) Vander Waals
(d) Vander Waals and covalent
Ans: d
Total number of crystal systems is
(a) 2
(b) 4
(c) 7
(d) 12
Ans: c
The number of atoms per unit cell in B.C.C. structure is
(a) 1
(b) 2
(c) 4
(d) 8
Ans: b
The conductivity of a metal is determined by
(a) the electronic concentration and the mobility of the free electrons
(6) the number of valence electrons per atom
(c) either (a) or (b)
(d) none of the above
Ans: a
The resistivity of a metal is a function of temperature because
(a) the amplitude of vibration of the atoms varies with temperature
(b) the electron density varies with temperature
(c) the electron gas density varies with temperature
Ans: a
In a crystal, an atom vibrates at a frequency determined by
(a) the heat content of the crystal
(b) the temperature of the crystal
(c) the stiffness of the bonds it makes with neighbors
Ans: c
Due to which of the following reasons aluminium does not corrode in atmosphere ?
(a) Aluminium is a noble metal
(b) Atmospheric oxygen can only diffuse very slowly through the oxide layer which is formed on the surface of aluminium
(c) No reaction with oxygen occurs ft Any of the above
Ans: b
The impurity atoms is semiconductors
(a) inject more charge carriers
(6) reduce the energy gap
(c) increase the kinetic energy of valence electrons
(d) all of the above
Ans: b
Which of the following material is not a semiconductor ?
(a) Silica
(b) Germanium
(c) Selenium
(d) Gallium-arsenide
Ans: a
Carbon resistors are used extensively because they are
(a) easy to make
(b) compact
(c) inexpensive
(d) all of the above reasons
Ans: d
Carbon rods are used in wet and dry cells because
(a) carbon rod serves as conductor
(b) carbon can resist the attack of battery acid
(c) both (a) and (b)
(d) either (a) or (b)
Ans: c
Due to which of the following factors the brush wear rate is altered ?
(a) Speed of the machine
(b) Contact pressure
(c) Surface conditions of brush and commutator
(d) Excessive sparking
(e) All of the above
Ans: e
Which of the following are non-conductors of electricity?
(a) Non-metal solids except carbon
(b) Air and most other gases
(c) Pure water and liquids in general except mercury
(d) All of the above
Ans: d
Carbon bearings are used under which of the following conditions ?
(a) Where lubrication is difficult or im-possible
(b) Where corrosive chemical action exists
(c) Where high temperature exists
(d) All of the above
Ans: d
Which of the following high resistance materials has the highest operating temperature ?
(a) Kanthal
(b) Manganin
(c) Nichrome
(d) Eureka
Ans: a
Steel wire is used as
(a) overhead telephone wire
(b) earth wire
(c) core wire of ACSR
(d) all of the above
Ans: d
Low resistivity materials are used in
(a) transformer, motor and generator windings
(b) transmission and distribution lines
(c) house wiring
(d) all above applications
Ans: d
Platinum is used in
(a) electrical contacts
(b) thermocouple
(c) heating element in high temperature furnace
(d) grids of special purpose vacuum tubes
(e) all of the above
Ans: e
Which of the following is an advantage of stranded conductor over equivalent single conductor ?
(a) Less liability to kink
(b) Greater flexibility
(c) Less liability to break
(d) All of the above
Ans: d
Due to which of the following reasons copper and aluminium are not used for heating elements ?
(a) Both have great tendency for oxidation
(b) Both have low melting point
(c) Very large length of wires will be required
(d) All of the above
Ans: d
Copper, even though costly, finds use in the windings of electrical machines because
(a) copper points offer low contact resistance
(b) copper can be easily soldered and welded
(e) copper windings are less bulky and the machines become compact
(d) all of the above
Ans: d
Which of the following materials is used for making coils of standard resistances ?
(a) Copper
(b) Nichrome
(c) Platinum
(d) Manganin
Ans: d
Substances whose specific resistance abruptly decreases at very low temperature are called
(a) insulators
(b) conductors
(c) semiconductors
(d) superconductors
Ans: d
Which of the following materials is the best conductor of electricity ?
(a) Tungsten
(b) Aluminium
(c) Copper
(d) Carbon
Ans: c
is the property of absorbing moisture from atmosphere.
(a) Solubility
(b) Viscosity
(c) Porosity
(d) Hygroscopicity
Ans: d
Thermocouples are mainly used for the measurement of
(a) temperature
(b) resistance
(c) eddy currents
(d) coupling co-efficient
Ans: a
Due to which of the following fact, in India, aluminium is replacing copper ?
(a) Aluminium is more ductile and malleable than copper
(6) Aluminium is available in plenty, cheaper and lighter than copper
(c) Aluminium has lower resistivity than that of copper
(d) Aluminium has less temperature co-efficient than copper
Ans: b
The conduction of electricity, in semiconductors, takes place due to movement of
(a) positive ions only
(b) negative ions only
(c) positive and negative ions
(d) electrons and holes
Ans: d
Which of the following is a semiconductor material ?
(a) Phosphorous
(b) Rubber
(c) Silicon
(d) Aluminium
Ans: c
Selenium is _____ semiconductor.
(a) extrnisic
(b) intmisic
(c) N-type
(d) P-type
Ans: b
________ has the best damping properties.
(a) Diamond
(b) High speed steel
(c) Mild steel
(d) Cast iron
Ans: d
The photo-electric effect occurs only when the incident light has more than a certain critical
(a) intensity
(b) speed
(c) frequency
(d) wave length
Ans: c
If the resistance of a conductor does not vary in accordance with Ohm’s law it is known as
(a) non-linear conductor
(b) reverse conductor
(c) bad-conductor
(d) non-conductor
Ans: a
Spark plug makes use of which of the following materials for insulation ?
(a) Porcelain
(b) Slate
(c) Asbestos
(d) Glass
Ans: a
The forbidden gap in an insulator is
(a) large
(b) small
(c) nil
(d) any of the above
Ans: a
Which of the following factors affect resistivity of metals ?
(a) Age hardening
(b) Alloying
(c) Temperature
(d) Cold work
(e) All of the above
Ans: e
Effect of moisture on the insulating materials is to
(a) decrease dielectric constant
(b) decrease dielectric strength
(c) decrease insulation resistance
(d) increase dielectric loss
(e) all of the above
Ans: e
Surface resistance of an insulating material is reduced due to the
(a) smoky and dirty atmosphere
(b) humidity in the atmosphere
(c) both (a) and (b)
(d) neither (a) nor (b)
Ans: c
Superconducting metal in super conducting state has relative permeability of
(a) zero
(b) one
(c) negative
(d) more than one
Ans: a
In conductors conduction of electricity takes place due to movement of
(a) electrons only
(b) positive ions only
(c) negative ions only
(d) positive and negative ions
(e) none of the above
Ans: a
The carbon percentage is least in
(a) low carbon steel
(b) wrought iron
(c) cast iron
(d) malleable iron
Ans: b
For a particular material the Hall coefficient was found to be zero. The material is
(a) insulator
(6) metal
(c) intrinsic semiconductor
(d) none of the above
Ans: b
The conductivity of an extrinsic semiconductor with temperature
(a) decreases
(b) increases
(c) remains constant
Ans: c
The current due to electron flow in conduction band is the hole current in valence band.
(a) equal to
(b) less than
(c) greater than
(d) any of the above
Ans: c
For a hole which of the following statements is incorrect ?
(a) Holes can exist in certain semiconductors only
(b) Holes can exist in any material including conductors
(c) Holes may constitute an electric current
(d) Holes can be considered as a net positive charge
Ans: b
is an element used in semiconductors whose atoms have three valence electrons.
(a) An acceptor
(b) A donor
(c) Germanium
(d) Silicon
Ans: a
The minority carrier concentration is largely a function of
(a) forward biasing voltage
(b) reverse biasing voltage
(c) temperature
(d) the amount of doping
Ans: c
For germanium the forbidden energy gap is
(a) 0.15 eV
(b) 0.25 eV
(C) 0.5eV
(d) 0.7eV
Ans: d

CABLES

The insulating material for a cable should have
(a) low cost
(b) high dielectric strength
(c) high mechanical strength
(d) all of the above
Ans: d
Which of the following protects a cable against mechanical injury ?
(a) Bedding
(b) Sheath
(c) Armouring
(d) None of the above
Ans: c
Which of the following insulation is used in cables ?
(a) Varnished cambric
(b) Rubber
(c) Paper
(d) Any of the above
Ans: d
Empire tape is
(a) varnished cambric
(b) vulcanised rubber
(c) impregnated paper
(d) none of the above
Ans: a
The thickness of the layer of insulation on the conductor, in cables, depends upon
(a) reactive power
(b) power factor
(c) voltage
(d) current carrying capacity
Ans: c
The bedding on a cable consists of
(a) hessian cloth
(b) jute
(c) any of the above
(d) none of the above
Ans: c
The insulating material for cables should
(a) be acid proof
(b) be non-inflammable
(c) be non-hygroscopic
(d) have all above properties
Ans: d
In a cable immediately above metallic sheath _____ is provided.
(a) earthing connection
(b) bedding
(c) armouring
(d) none of the above
Ans: b
The current carrying capacity of cables in D.C. is more thanthat in A.C. mainly due to
(a) absence of harmonics
(b) non-existence of any stability limit
(c) smaller dielectric loss
(d) absence of ripples
(e) none of the above
Ans: c
In case of three core flexible cable the colour of the neutral is
(a) blue
(b) black
(c) brown
(d) none of the above
Ans: a
cables are used for 132 kV lines.
(a) High tension
(b) Super tension
(c) Extra high tension
(d) Extra super voltage
Ans: d
Conduit pipes are normally used to protect _____ cables.
(a) unsheathed cables
(b) armoured
(c) PVC sheathed cables
(d) all of the above
Ans: a
The minimum dielectric stress in a cable is at
(a) armour
(b) bedding
(c) conductor surface
(d) lead sheath
Ans: d
In single core cables armouring is not done to
(a) avoid excessive sheath losses
(b) make it flexible
(c) either of the above
(d) none of the above
Ans: a
Dielectric strength of rubber is around
(a) 5 kV/mm
(b) 15 kV/mm
(c) 30 kV/mm
(d) 200 kV/mm
Ans: c
Low tension cables are generally used up to
(a) 200 V
(b) 500 V
(c) 700 V
(d) 1000 V
Ans: d
In a cable, the maximum stress under operating conditions is at
(a) insulation layer
(b) sheath
(c) armour
(d) conductor surface
Ans: d
High tension cables are generally used up to
(a) 11kV
(b) 33kV
(c) 66 kV
(d) 132 kV
Ans: a
The surge resistance of cable is
(a) 5 ohms
(b) 20 ohms
(c) 50 ohms
(d) 100 ohms
Ans: c
PVC stands for
(a) polyvinyl chloride
(b) post varnish conductor
(c) pressed and varnished cloth
(d) positive voltage conductor
(e) none of the above
Ans: a

In the cables, the location of fault is usually found out by comparing
(a) the resistance of the conductor
(b) the inductance of conductors
(c) the capacitances of insulated conductors
(d) all above parameters
Ans: c

In capacitance grading of cables we use a ______ dielectric.
(a) composite
(b) porous
(c) homogeneous
(d) hygroscopic
Ans: a
Pressure cables are generally not used beyond
(a) 11 kV
(b) 33 kV
(c) 66 kV
(d) 132 kV
Ans: c
The material for armouring on cable is usually
(a) steel tape
(b) galvanised steel wire
(c) any of the above
(d) none of the above
Ans: c
Cables, generally used beyond 66 kV are
(a) oil filled
(b) S.L. type
(c) belted
(d) armoured
Ans: a
The relative permittivity of rubber is
(a) between 2 and 3
(b) between 5 and 6
(c) between 8 and 10
(d) between 12 and 14
Ans: a
Solid type cables are considered unreliable beyond 66 kV because
(a) insulation may melt due to higher temperature
(b) skin effect dominates on the conductor
(c) of corona loss between conductor and sheath material
(d) there is a danger of breakdown of insulation due to the presence of voids
Ans: d
If the length of a cable is doubled, its capacitance
(a) becomes one-fourth
(b) becomes one-half
(c) becomes double
(d) remains unchanged
Ans: c
In cables the charging current
(a) lags the voltage by 90°
(b) leads the voltage by 90°
(c) lags the voltage by 180°
(d) leads the voltage by 180°
Ans: b
A certain cable has an insulation of relative permittivity 4. If the insulation is replaced by one of relative permittivity 2, the capacitance of the cable will become
(a) one half
(6) double
(c) four times
(d) none of the above
Ans: a
If a cable of homogeneous insulation has a maximum stress of 10 kV/mm, then the dielectric strength of insulation should be
(a) 5 kV/mm
(b) 10 kV/mm
(a) 15 kV/mm
(d) 30 kV/mm
Ans: b
In the cables, sheaths are used to
(a) prevent the moisture from entering the cable
(b) provide enough strength
(e) provide proper insulation
(d) none of the above
Ans: a
The intersheaths in the cables are used to
(a) minimize the stress
(b) avoid the requirement of good insulation
(c) provide proper stress distribution
(d) none of the above
Ans: c
The electrostatic stress in underground cables is
(a) same at the conductor and the sheath
(b) minimum at the conductor and maximum at the sheath
(c) maximum at the conductor and minimum at the sheath
(d) zero at the conductor as well as on the sheath
(e) none of the above
Ans: c
The breakdown of insulation of the cable can be avoided economically by the use of
(a) inter-sheaths
(b) insulating materials with different dielectric constants
(c) both (a) and (b)
(d) none of the above
Ans: c
The insulation of the cable decreases with
(a) the increase in length of the insulation
(b) the decrease in the length of the insulation
(c) either (a) or (b)
(d) none of the above
Ans: a
A cable carrying alternating current has
(a) hysteresis losses only
(b) hysteresis and leakage losses only
(c) hysteresis, leakage and copper losses only
(d) hysteresis, leakage, copper and friction losses
Ans: b
In a cable the voltage stress is maximum at
(a) sheath
(6) insulator
(e) surface of the conductor
(d) core of the conductor
Ans: d
Capacitance grading of cable implies
(a) use of dielectrics of different permeabilities
(b) grading according to capacitance of cables per km length
(c) cables using single dielectric in different concentrations
(d) capacitance required to be introduced at different lengths to counter the effect of inductance
(e) none of the above
Ans: a
Underground cables are laid at sufficient depth
(a) to minimise temperature stresses
(b) to avoid being unearthed easily due to removal of soil
(c) to minimise the effect of shocks and vibrations due to gassing vehicles, etc.
(d) for all of the above reasons
Ans: c
The advantage of cables over overhead transmission lines is
(a) easy maintenance
(b) low cost
(c) can be used in congested areas
(d) can be used in high voltage circuits
Ans: c
The thickness of metallic shielding on cables is usually
(a) 0.04 mm
(b) 0.2 to 0.4 mm
(e) 3 to 5 mm
(d) 40 to 60 mm
Ans: a
Cables for 220 kV lines are invariably
(a) mica insulated
(b) paper insulated
(c) compressed oil or compressed gas insulated
(d) rubber insulated
(e) none of the above
Ans: c
Is a cable is to be designed for use on 1000 kV, which insulation would you prefer ?
(a) Polyvinyle chloride
(b) Vulcanised rubber
(c) Impregnated paper
(d) Compressed SFe gas
(e) none of the above
Ans: d
If a power cable and a communication cable are to run parallel the minimum distance between the two, to avoid interference, should be
(a) 2 cm
(b) 10 cm
(c) 50 cm
(d) 400 cm
Ans: c
Copper as conductor for cables is used as
(a) annealed
(b) hardened and tempered
(c) hard drawn
(d) alloy with chromium
Ans: a
The insulating material should have
(a) low permittivity
(b) high resistivity
(c) high dielectric strength
(d) all of the above
Ans: d
The advantage of oil filled cables is
(a) more perfect impregnation
(b) smaller overall size
(c) no ionisation, oxidation and formation of voids
(d) all of the above
Ans: d
The disadvantage with paper as insulating material is
(a) it is hygroscopic
(6) it has high capacitance
(c) it is an organic material
(d) none of the above
Ans: a
The breakdown voltage of a cable depends on
(a) presence of moisture
(b) working temperature
(c) time of application of the voltage
(d) all of the above
Ans: d
It is difficult to maintain oil filled cables.
(a) Yes
(b) No
Ans: a
In capacitance grading a homogeneous dielectric is used.
(a) Yes
(b) No
Ans: b
In congested areas where excavation is expensive and inconvenient ‘draw in system’ of laying of underground cables is often adopted.
(a) Yes
(b) No
Ans: a
Natural rubber is obtained from milky sap of tropical trees.
(a) Yes
(b) No
Ans: a
Rubber is most commonly used insulation in cables.
(a) Yes
(b) No
Ans: a
Polyethylene has very poor dielectric and ageing properties.
(a) Yes
(b) No
Ans: b
The metallic sheath may be made of lead or lead alloy or of aluminium.
(a) Yes
(b) No
Ans: b

Electrical Machine Design

Which of the following is the major consideration to evolve a good design ?
(a) Cost
(b) Durability
(c) Compliance with performance criteria as laid down in specifications
(d) All of the above
Ans: d

2 impose limitation on design.
(a) Saturation
(b) Temperature rise
(c) Efficiency
(d) Power factor
(e) All above
Ans: e

The efficiency of a machine should be as ______ as possible to reduce the operating cost.
(a) high
(b) low
(c) either of the above
(d) none of the above
Ans: a
If an insulating material is operated beyond the maximum allowable temperature, its life is
(a) drastically increased
(b) drastically reduced
(c) unaffected
(d) none of the above
Ans: b
The design of mechanical parts is particularly important in case of _____ speed machines.
(a) low
(b) medium
(c) high
(d) any of the above
Ans: c
In induction motors, the length of air gap in kept as small as mechanically possible is order to have
(a) low power factor
(b) high power factor
(c) high over load capacity
(d) any of the above
Ans: b
In ______ machines, the size of the shaft is decided by the critical speed which depends on the deflection of the shaft.
(a) small
(b) medium
(c) large
(d) any of the above.
Ans: c
The length cf air gap to be provided in ______ is primarily determined by power factor consideration.
(a) d.c. series motor .
(b) d.c. shunt motor
(c) induction motor
(d) synchronous motor
Ans: c
Electrical machines having a power output up to about 750 W may be called_______machines.
(a) small size
(b) medium size
(c) large size
(d) any of the above
Ans: a
Electrical machines having power outputs ranging from a few kW up to approximately 250 kW may be classified as
(a) small size machines
(b) medium size machines
(c) large size machines
(d) any of the above
Ans: b
Commercial available medium size machines have a speed range of ______ .
(a) 200 to 400 r.p.m.
(b) 600 to 1000 r.p.m.
(c) 1000 to 1500 r.p.m.
(d) 2000 to 2500 r.p.m.
Ans: d
The action of electromagnetic machines can be related to which of the following basic principles ?
(a) Induction
(b) Interaction
(c) Alignment
(d) All of the above
Ans: d
The change in flux linkages can be caused in which of the following ways ?
(a) The flux is constant with respect to time and is stationary and the coil moves through it
(b) The coil is stationary with respect to flux and the flux varies in magnitude with respect to time
(c) Both the changes mentioned above occur together, i.e., the coil moves through a time varying field
(d) All of the above
Ans: d

14 is universally used for windings of electrical machines because it is easily workable without any possibility of
fracture.
(a) Silver
(b) Steel
(c) Aluminium
(d) Copper
Ans: d

Aluminium when adopted as a conductor material in ______ transformers, decreases the overall cost of the transformer
(a) small size
(b) medium size
(c) large size
(d) any of the above size
Ans: a
Which of the following materials is used in the manufacture of resistance grids to be used in the starters of large motors ?
(a) Copper
(b) Aluminium
(c) Steel
(d) Cast-iron
Ans: d
Materials exhibiting zero value of resistivity are known as ______ .
(a) conductors
(b) semiconductors
(c) insulators
(d) superconductors
Ans: d
________ has a lowrelative permeability and is used principally in field frames when cost is of primary importance and extra weight is not objectionable.
(a) Cast steel
(b) Aluminium
(c) Soft steel
(d) Cast iron
Ans: d

19 ______is extensively used for those portions of magnetic circuit which carry steady flux and need superior mechanical properties ?
(a) Grey cast-iron
(b) Cast steel
(c) High carbon steel
(d) Stainless steel
Ans: b

Hot rolled sheets have ______ value of permeability
(a) zero
(b) low
(c) high
(d) none of the above
Ans: b
The heated parts of an electrical machine dissipate heat into their surroundings by which of the following modes of heat dissipation ?
(a) Conduction
(b) Convection
(c) Radiation
(d) All of the above
Ans: d
The heat dissipated by from a surface depends upon its temperature and its characteristics like colour, roughness etc.
(a) conduction
(b) convection
(c) radiation
(d) any of the above
Ans: c
The mcrease in heat dissipation by air blasts is due to increase in
(a) conduction
(b) convection
(e) radiation
(d) any ofthe above
Ans: b
On which of the following variables heat convected depends ?
(a) Power density
(b) Temperature difference between heated surface and coolant
(c) Thermal resistivity, density, specific heat
(d) Gravitational constant
(e) All of the above
Ans: e
Which of the following methods is used for air cooling of turbo-alternators ?
(a) One sided axial ventilation
(b) Two sided axial ventilation
(c) Multiple inlet system
(d) All of the above
Ans: d
Multiple inlet system of air cooling of turbo-alternators can be used for machines of rating upto
(a) 10 MW
(b) 30 MW
(c) 60 MW
(d) 150 MW
Ans: c
Which of the following is an advantage of hydrogen cooling ?
(a) Increase in efficiency
(b) Increase in ratings
(c) Increase in life
(d) Smaller size of coolers
(e) All of the above
Ans: e
The density of hydrogen is _____ times the density of air.
(a) 0.07
(b) 1.5
(c) 2.5
(d) 3.5
Ans: a
Hydrogen has a heat transfer co-efficient _____ times that of air
(a) 1.5
(b) 2.5
(c) 3.5
(d) 4.5
Ans: a
The thermal conductivity of hydrogen is ______ times that of air
(a) 2
(b) 3
(c) 5
(d) 7
Ans: d
With conventional hydrogen cooling it is possible to increase the rating of a single unit to
(a) 50 MW
(b) 100 MW
(c) 200 MW
(d) none of the above
Ans: c
The noise produced by a ______ cooled machine is less as the rotor moves in a medium of smaller density.
(a) air
(b) hydrogen
(c) either (a) or (b)
(d) none of the above
Ans: b
cooling is the process of dissipating the armature and field winding losses to a cooling medium circulating within the winding insulation wall
(a) Direct
(b) Indirect
(c) Conventional
(d) Any of the above
Ans: a
Machines cooled by direct cooling method may be called
(a) “supercharged”
(b) “inner cooled”
(c) “conductor cooled”
(d) any of the above
Ans: d
In direct cooled system using hydrogen both stator and rotor conductors are made
(a) solid
(b) hollow
(c) perforated
(d) any ofthe above
Ans: b
With direct water cooling it is possible to have ratings of about
(a) 200 MW
(b) 300 MW
(c) 400 MW
(d) 600 MW
Ans: d
The resistivity of water should not be less than
(a) 10 Q m
(b) 100 Q m
(c) 1000 Q m
(d) 2000 Q m
Ans: d
Direct water cooling of rotor winding presents
(a) no mechanical difficulties
(b) lesser mechanical difficulties
(c) greater mechanical difficulties
(d) none of the above
Ans: c
The time taken by the machine to attain 0.632 of its final steady temperature rise is called
(a) heating time constant
(b) cooling time constant
(c) either (a) or (b)
(d) none of the above
Ans: a
In self cooled motors the cooling time constant is about ______ than the heating time constant because cooling conditions are worse at standstill.
(a) 2 to 3 times greater
(b) 3 to 4 times greater
(c) 4 to 5 times greater
(d) none of the above
Ans: a
By which of the following methods motor rating for variable load drives can be determined ?
(a) Method of average losses
(b) Equivalent current method
(c) Equivalent torque method
(d) Equivalent power method
(e) All of the above.
Ans: e
Which of the following methods does not take into account the maximum temperature rise under variable load conditions ?
(a) Equivalent power method
(b) Equivalent current method
(c) Method of average losses
(d) Equivalent torque method
Ans: c
Which of the following methods is most accurate ?
(a) Equivalent current method
(b) Equivalent power method
(c) Equivalent torque method
(d) Method of average losses
Ans: a
By which of the following methods the temperature rise of windings and other parts may be determined ?
(a) Thermometer method
(6) Resistance method
(c) Embedded temperature detector method
(d) Any of the above
Ans: d
The slot leakage can be calculated by making which of the following assumptions ?
(a) The current in the slot conductors is uniformly distributed over their cross-section
(b) The leakage path is straight across the slot and around the iron at the bottom
(c) The permanence of air paths is only considered. The reluctance of iron paths is assumed as zero
(d) All of the above
Ans: d
The value of exciting or magnetizing current depends upon which of the following factors ?
(a) Total m.m.f. required
(b) The number of turns in the exciting winding
(c) The way in which the winding is distributed
(d) All of the above
Ans: d
Tractive magnets are operated from
(a) a.c. supply
(b) d.c. supply
(c) either a.c. or d.c. supply
(d) none of the above
Ans: c
electromagnets generally function as holding magnets.
(a) Tractive
(b) Portative
(c) Either of the above
(d) None of the above
Ans: b
Which of the following is the commonly used type of electromagnets ?
(a) Flat-faced armature type
(b) Horse shoe type
(c) Flat-faced plunger type
(d) All of the above
Ans: d
are used for construction of core of electromagnets.
(a) Soft magnetic materials
(b) Hard magnetic materials
(c) Either (a) or (b)
(d) None of the above
Ans: a
The design of electromagnets is based upon which of the following fundamental equations ?
(a) Force equation
(b) Magnetic circuit equation
(c) Heating equation
(d) Voltage equation
(e) All of the above
Ans: e
When the two coil sides forming a coil are spaced exactly one pole pitch apart they are said to be of
(a) short pitch
(b) full pitch
(c) either of the above
(d) none of the above
Ans: b
are always double layer type.
(a) Closed windings
(b) Open windings
(c) Either of the above
(d) None of the above
Ans: a
The distance between the starts of two consecutive coils measured in terms of coil sides is called
(a) front pitch
(b) winding pitch
(c) commutator pitch
(d) back pitch
Ans: b
The winding where dummy coils are used is sometimes called
(a) duplex winding
(b) triplex winding
(c) forced winding
(d) none of the above
Ans: c
Dummy coil should not be used in
(a) small machines
(b) large machines
(c) either (a) or (b)
(d) none of the above
Ans: b
Power transformers have rating
(a) equal to 50 kVA
(6) equal to 100 kVA
(c) above 200 kVA
(d) none of the above
Ans: c
Power transformers should be designed to have maximum efficiency
(a) at one-fourth load
(b) at one-half load
(c) at or near full load
(d) any of the above
Ans: c
In transformers using hot rolled steel, the cross-section of the yoke is made about _____ greater than that of the core
(a) 5 percent
(b) 10 percent
(c) 15 percent
(d) 30 percent
(e) none of the above
Ans: c
Yokes with rectangular cross-section are used for
(a) small capacity transformers
(b) medium capacity transformers
(c) large capacity transformers
(d) any of the above
Ans: a
The cold rolled grain oriented steel has ______ permeability in the direction of the grain orientation.
(a) minimum
(b) maximum
(c) nil
(d) none of the above
Ans: b
Cylindrical windings using circular conductors, employed in transformers, are
(a) single layered
(b) double layered
(c) multi-layered
(d) none of the above
Ans: c
Helical windings are used in
(a) distribution transformers
(b) power transformers
(c) shell type transformers
(d) none of the above
Ans: b
Multi-layer helical windings are commonly used in the transformers as high voltage windings
(a) upto 20 kV
(b) upto 50 kV
(c) upto 80 kV
(d) for 110 kV and above
Ans: d
Disc windings are primarily used in
(a) short capacity transformers
(b) medium capacity transformers
(c) high capacity transformers
(d) any of the above
Ans: c
The heat dissipating capability of transformers of ratings higher than 30 kVA in increased by providing which of
the following ?
(a) Corrugations
(b) Fins
(c) Tubes
(d) Radiator tanks
(e) All of the above
Ans: e
Transformers with a capacity of up to _____ have a cooling radiator system with natural cooling
(a) 2 MVA
(b) 5 MVA
(c) 7.5 MVA
(d) 10 MVA
Ans: d
The forced oil and air circulation method is usual one for transformers of capacities
(a) upto 5 MVA
(b) upto 10 MVA
(c) upto 20 MVA
(d) 30 MVA upwards
Ans: d
The flash point of transformer oil should be higher than
(a) 40°C
(b) 60°C
(c) 80°C
(d) 104°C
Ans: d
The voltage control in electric supply networks in required on account of which of the following reasons ?
(a) Adjustment of voltage at consumers premises within statutory limits
(b) Control of active and reactive power
(c) Adjustment of short period daily and seasonal voltage variations in accordance with variations of load
(d) All of the above
Ans: d
D.C. windings are
(a) sometimes 2-layer type
(b) never 2-layer type
(c) always 2-layer type
(d) none of the above
Ans: c
The usual values of maximum flux densities for distribution transformers using hot rolled silicon steel are
(a) 0.5 to 0.8 Wb/m2
(b) 0.8 to 1.0 Wb/m2
(c) 1.1 to 1.35 Wb/m2
(d) 1.4 to 1.8 Wb/m2
Ans: c
For 275 kV transformers, using cold rolled grain oriented steel, which of the following values of flux density may be used?
(a) 1.0 Wb/m2
(b) 1.1 Wb/m2
(c) 1.3 Wb/m2
(d) 1.6 Wb/m2
(e) None of the above
Ans: d
For large power transformers, self oil cooled type or air blast type which of the following values of current density may be used ?
(a) 1.0 to 1.2 A/mm2
(b) 1.5 to 2.0 A/mm2
(c) 2.2 to 3.2 A/mm2
(d) 3.2 to 4.2 A/mm2
Ans: c
A current density of _____ is ilsed for large power transformers with forced circulation of oil or with water cooling coils
(a) 1.5 to 2.5 A/mm2
(b) 3.5 to 4.5 A/mm2
(c) 4.0 to 5.0 A/mm2
(d) 5.4 to 6.2 A/mm2
Ans: d
The high voltage winding is usually which of the following type ?
(a) Cylindrical winding with circular conductors
(b) Cross-over winding with either circular or small rectangular conductors
(c) Continuous disc type winding with rectangular conductors
(d) All of the above types
Ans: d
Which of the following is the basic consideration in the design of insulation ?
(a) Electrical considerations
(b) Mechanical considerations
(c) Thermal considerations
(d) All of the above
Ans: d
A practical formula for determining the thickness of insulation between low voltage and high voltage windings is
(a) 1 + 0.2 kVmm
(6) 2 + 0.5 kVmm
(c) 4 + 0.7 kV mm
(d) 5 + 0.9 kV mm
Ans: d
The insulation between windings and grounded core and the insulation between the windings of the same phase is
called
(a) minor insulation
(b) major insulation
(c) either of the above
(d) none of the above
Ans: b
The cylindrical windings using circular conductors are used for current rating of
(a) upto 20 A
(b) upto 40 A
(c) upto 60 A
(d) upto 80 A
Ans: d
The surge phenomenon is particularly important in case of
(a) low voltage transformers
(b) medium voltage transformers
(c) high voltage transformers
(d) any of the above
Ans: c
Which of the following in an application of D.C. motors?
(a) Traction
(b) Drives for process industry
(c) Battery driven vehicles
(d) Automatic control
(e) All of the above
Ans: e
D.C. servomotors are used in
(a) purely D.C. control systems
(6) purely AC. control systems
(c) both D.C. and AC. control systems
(d) none of the above
Ans: a
The stator of a D.C. machine comprises of
(a) main poles
(6) interpoles
(c) frame
(d) all of the above
Ans: d
The laminations of the armature of a D.C. machine are usually _____ thick.
(a) 0.1 to 0.2 mm
(b) 0.2 to 0.3 mm
(c) 0.3 to 0.4 mm
(d) 0.4 to 0.5 mm
Ans: d
is usually used for brush rockers
(a) Mild steel
(b) Copper
(c) Aluminium
(d) Cast-iron
Ans: d
______ brushes are fragile and cause excessive wear of commutator,
(a) Natural graphite
(b) Hard carbon
(c) Electro graphitic
(d) Metal graphite
Ans: a
Which of the following brushes can be used for high values of current density ?
(a) Metal graphite brushes
(b) Hard carbon brushes
(c) Electro-graphitic brushes
(d) Natural graphite brushes
Ans: a
________ is the common method of applying brushes to the commntator.
(a) Radial
(b) Trailing
(c) Reaction
(d) All of the above
Ans: d
Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ?
(a) Increased I R losses
(b) Increased core losses
(c) Poor commutation
(d) Change in motor parameters
(e) All of the above
Ans: e
The weight of copper of both armature and field windings decreases with _____ in number of poles.
(a) increase
(b) decrease
(c) either of the above
(d) none of the above
Ans: a
In a D.C. machine the number of brush arms is _____ the number of poles.
(a) less than
(b) equal to
(c) greater than
(d) none of the above
Ans: b
In a D.C. machine the current per brush arm should not be more than
(a) 100 A
(6) 200 A
(e) 300 A
(d) 400 A
Ans: d
In a D.C. machine, the value of peripheral speed should not, normally, exceed
(a) 10 m/s
(b) 20 m/s
(c) 30 m/s
(d) 40 m/s
Ans: c
In D.C. machines the width of the duct is usually
(a) 4 mm
(b) 6 mm
(c) 8 mm
(d) 10 mm
Ans: d
D.C. machines designed with a large value of air gap length have
(a) worst, ventilation
(b) poor ventilation
(c) better ventilation
(d) none of the above
Ans: c
In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made
(a) equal to that of armature mmf
(b) less in comparison with the armature mmf
(c) large in comparison with the armature mmf
(d) none of the above
Ans: c
In D.C. machines, the ____ in field mmf results in increase in size and cost of machines.
(a) increase
(b) decrease
(c) either of the above
(d) none of the above
Ans: a
The operation of a D.C. machine with large air gap lengths is comparatively
(a) quiet
(b) noisy
(c) either of the above
(d) none of the above
Ans: a
Which of the following methods may be adopted to reduce the effects of armature reaction ?
(a) Increase in length of air gap at pole tips
(b) Increasing reluctance of pole tips
(c) Compensating windings
(d) Interpoles
(e) All of the above
Ans: e
In D.C. machines the usual limit of slot pitch is
(a) between 5 to 10 mm
(b) between 10 to 15 mm
(c) between 15 to 20 mm
(d) between 25 to 35 mm
Ans: d
In D.C. machines the number of slots per pole usually lies
(a) between 2 to 4
(b) between 6 to 8
(c) between 9 to 16
(d) between 20 to 30
Ans: c

Measurement and Instrumentation

The use of _____ instruments is merely confined within laboratories as standardizing instruments.
(a) absolute
(b) indicating
(c) recording
(d) integrating
(e) none of the above
Ans: a
Which of the following instruments indicate the instantaneous value of the electrical quantity being measured at the time at which it is being measured ?
(a) Absolute instruments
(b) Indicating instruments
(c) Recording instruments
(d) Integrating instruments
Ans: b
_____ instruments are those which measure the total quantity of electricity delivered in a particular time.
(a) Absolute
(b) Indicating
(c) Recording
(d) Integrating
Ans: d
Which of the following are integrating instruments ?
(a) Ammeters
(b) Voltmeters
(c) Wattmeters
(d) Ampere-hour and watt-hour meters
Ans: d
Resistances can be measured with the help of
(a) wattmeters
(b) voltmeters
(c) ammeters
(d) ohmmeters and resistance bridges
(e) all of the above
Ans: d

6 According to application, instruments are classified as
(a) switch board
(b) portable
(c) both (a) and (b)
(d) moving coil
(e) moving iron
(f) both (d) and (e)
Ans: c

Which of the following essential features is possessed by an indicating instrument ?
(a) Deflecting device
(b) Controlling device
(c) Damping device
(d) All of the above
Ans: d
A _____ device prevents the oscillation of the moving system and enables the latter to reach its final position quickly
(a) deflecting
(b) controlling
(c) damping
(d) any of the above
Ans: c
The spring material used in a spring control device should have the following property.
(a) Should be non-magnetic
(b) Most be of low temperature co-efficient
(c) Should have low specific resistance
(d) Should not be subjected to fatigue
(e) All of the above
Ans: e
Which of the following properties a damping oil must possess ?
(a) Must be a good insulator
(b) Should be non-evaporating
(c) Should not have corrosive action upon the metal of the vane
(d) The viscosity of the oil should not change with the temperature
(e) All of the above
Ans: e
A moving-coil permanent-magnet instrument can be used as _____ by using a low resistance shunt.
(a) ammeter
(b) voltmeter
(c) flux-meter
(d) ballistic galvanometer
Ans: a
A moving-coil permanent-magnet instrument can be used as flux-meter
(a) by using a low resistance shunt
(b) by using a high series resistance
(c) by eliminating the control springs
(d) by making control springs of large moment of inertia
Ans: c
Which of the following devices may be used for extending the range of instruments ?
(a) Shunts
(b) Multipliers
(c) Current transformers
(d) Potential transformers
(e) All of the above
Ans: e
An induction meter can handle current up to
(a) 10 A
(b) 30 A
(c) 60 A
(d) 100 A
Ans: d
For handling greater currents induction wattmeters are used in conjunction with
(a) potential transformers
(b) current transformers
(c) power transformers
(d) either of the above
(e) none of the above
Ans: b
Induction type single phase energy meters measure electric energy in
(a) kW
(b) Wh
(c) kWh
(d) VAR
(e) None of the above
Ans: c
Most common form of A.C. meters met with in every day domestic and industrial installations are
(a) mercury motor meters
(b) commutator motor meters
(c) induction type single phase energy meters
(d) all of the above
Ans: c
Which of the following meters are not used on D.C. circuits
(a) Mercury motor meters
(b) Commutator motor meters
(c) Induction meters
(d) None of the above
Ans: c
Which of the following is an essential part of a motor meter ?
(a) An operating torque system
(b) A braking device
(c) Revolution registering device
(d) All of the above
Ans: d
A potentiometer may be used for
(a) measurement of resistance
(b) measurement of current
(c) calibration of ammeter
(d) calibration of voltmeter
(e) all of the above
Ans: e

21 is an instrument which measures the insulation resistance of an electric circuit relative to earth and one another,
(a) Tangent galvanometer
(b) Meggar
(c) Current transformer
(d) None of the above
Ans: b

The household energy meter is
(a) an indicating instrument
(b) a recording instrument
(c) an integrating instrument
(d) none of the above
Ans: c
The pointer of an indicating instrument should be
(a) very light
(b) very heavy
(c) either (a) or (b)
(d) neither (a) nor (b)
Ans: a
The chemical effect of current is used in
(a) D.C. ammeter hour meter
(b) D.C. ammeter
(c) D.C. energy meter
(d) none of the above
Ans: a
In majority of instruments damping is provided by
(a) fluid friction
(b) spring
(c) eddy currents
(d) all of the above
Ans: c
An ammeter is a
(a) secondary instrument
(b) absolute instrument
(c) recording instrument
(d) integrating instrument
Ans: a
In a portable instrument, the controlling torque is provided by
(a) spring
(b) gravity
(c) eddy currents
(d) all of the above
Ans: a
The disc of an instrument using eddy current damping should be of
(a) conducting and magnetic material
(b) non-conducting and magnetic material
(c) conducting and non-magnetic material
(d) none of the above
Ans: c
The switch board instruments
(a) should be mounted in vertical position
(6) should be mounted in horizontal position
(c) either (a) or (b)
(d) neither (a) nor (b)
Ans: a
The function of shunt in an ammeter is to
(a) by pass the current
(b) increase the sensitivity of the ammeter
(c) increase the resistance of ammeter
(d) none of the above
Ans: a
The multiplier and the meter coil in a voltmeter are in
(a) series
(b) parallel
(c) series-parallel
(d) none of the above
Ans: a
A moving iron instrument can be used for
(a) D.C. only
(b) A.C. only
(c) both D.C. and A.C.
Ans: c
The scale of a rectifier instrument is
(a) linear
(b) non-linear
(c) either (a) or (b)
(d) neither (a) nor (b)
Ans: a
For measuring current at high frequency we should use
(a) moving iron instrument
(b) electrostatic instrument
(c) thermocouple instrument
(d) none of the above
Ans: c
The resistance in the circuit of the moving coil of a dynamometer wattmeter should be
(a) almost zero
(b) low
(c) high
(d) none of the above
Ans: c
A dynamometer wattmeter can be used for
(a) both D.C. and A.C.
(b) D.C. only
(c) A.C. only
(d) any of the above
Ans: a
An induction wattmeter can be used for
(a) both D.C. and A.C.
(6) D.C. only
(c) A.C. only
(d) any of the above
Ans: b
The pressure coil of a wattmeter should be connected on the supply side of the current coil when
(a) load impedance is high
(b) load impedance is low
(c) supply voltage is low
(d) none of the above
Ans: a
In a low power factor wattmeter the pressure coil is connected
(a) to the supply side of the current coil
(b) to the load side of the current coil
(c) in any of the two meters at connection
(d) none of the above
Ans: b
In a low power factor wattmeter the compensating coil is connected
(a) in series with current coil
(b) in parallel with current coil
(c) in series with pressure coil
(d) in parallel with pressure coil
Ans: c
In a 3-phase power measurement by two wattmeter method, both the watt meters had identical readings. The
power factor of the load was
(a) unity
(6) 0.8 lagging
(c) 0.8 leading
(d) zero
Ans: a
In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The
power factor of the load must be
(a) unity
(b) 0.5
(c) 0.3
(d) zero
Ans: b
The adjustment of position of shading bands, in an energy meter is done to provide
(a) friction compensation
(b) creep compensation
(c) braking torque
(d) none of the above
Ans: a
An ohmmeter is a
(a) moving iron instrument
(b) moving coil instrument
(c) dynamometer instrument
(d) none of the above
Ans: b
When a capacitor was connected to the terminal of ohmmeter, the pointer indicated a low resistance initially and then slowly came to infinity position. This shows that capacitor is
(a) short-circuited
(b) all right
(c) faulty
Ans: b
For measuring a very high resistance we should use
(a) Kelvin’s double bridge
(b) Wheat stone bridge
(c) Meggar
(d) None of the above
Ans: c
The electrical power to a meggar is provided by
(a) battery
(b) permanent magnet D.C. generator
(c) AC. generator
(d) any of the above
Ans: b
In a meggar controlling torque is provided by
(a) spring
(b) gravity
(c) coil
(d) eddy current
Ans: c
The operating voltage of a meggar is about
(a) 6 V
(b) 12 V
(c) 40 V
(d) 100 V
Ans: d
Murray loop test can be used for location of
(a) ground fault on a cable
(b) short circuit fault on a cable
(c) both the ground fault and the short-circuit fault
(d) none of the above
Ans: c
Which of the following devices should be used for accurate measurement of low D.C. voltage ?
(a) Small range moving coil voltmeter
(b) D.C. potentiometer
(c) Small range thermocouple voltmeter
(d) None of the above
Ans: b
It is required to measure the true open circuit e.m.f. of a battery. The best device is
(a) D.C. voltmeter
(b) Ammeter and a known resistance
(c) D.C. potentiometer
(d) None of the above
Ans: c
A voltage of about 200 V can be measured
(a) directly by a D.C. potentiometer
(b) a D.C. potentiometer in conjunction with a volt ratio box
(c) a D.C. potentiometer in conjunction with a known resistance
(d) none of the above
Ans: b
A direct current can be measured by
(a) a D.C. potentiometer directly
(b) a D.C. potentiometer in conjunction with a standard resistance
(c) a D.C. potentiometer in conjunction with a volt ratio box
(d) none of the above
Ans: b
To measure a resistance with the help of a potentiometer it is
(a) necessary to standardise the potentiometer
(b) not necessary to standardise the potentiometer
(c) necessary to use a volt ratio box in conjunction with the potentiometer
(d) none of the above
Ans: b
A phase shifting transformer is used in conjunction with
(a) D.C. potentiometer
(b) Drysdale potentiometer
(c) A.C. co-ordinate potentiometer
(d) Crompton potentiometer
Ans: b
Basically a potentiometer is a device for
(a) comparing two voltages
(b) measuring a current
(c) comparing two currents
(d) measuring a voltage
(e) none of the above
Ans: a
In order to achieve high accuracy, the slide wire of a potentiometer should be
(a) as long as possible
(b) as short as possible
(c) neither too small not too large
(d) very thick
Ans: a
To measure an A. C. voltage by using an A.C. potentiometer, it is desirable that the supply for the potentiometer in taken
(a) from a source which is not the same as the unknown voltage
(b) from a battery
(c) from the same source as the unknown voltage
(d) any of the above
Ans: c
The stator of phase shifting transformer for use in conjunction with an A.C. potentiometer usually has a
(a) single-phase winding
(b) two-phase winding
(c) three-phase winding
(d) any of the above
Ans: b
In an AC. co-ordinate potentiometer, the currents in the phase and quadrature potentiometer are adjusted to be
(a) out of phase by 90°
(6) out of phase by 60°
(c) out of phase by 30°
(d) out of phase by 0°
(e) out of phase by 180°
Ans: a
A universal RLC bridge uses
(a) Maxwell bridge configuration for measurement of inductance and De Santas bridge for measurement of capacitance
(b) Maxwell Wein bridge for measurement of inductance and modified De Santy’s bridge for measurement of capacitance
(c) Maxwell Wein bridge for measurement of inductance and Wein bridge for measurement of capacitance
(d) Any of the above.
Ans: b
For measurements on high voltage capacitors, the suitable bridge is
(a) Wein bridge
(b) Modified De Santy’s bridge
(c) Schering bridge
(d) Any of the above
(e) None of the above
Ans: c
In an Anderson bridge, the unknown inductance is measured in terms of
(a) known inductance and resistance
(b) known capacitance and resistance
(c) known resistance
(d) known inductance
Ans: b
Wagner earthing device is used to eliminate errors due to
(a) electrostatic coupling
(b) electromagnetic coupling
(c) both (a) and (b)
(d) none of the above
Ans: a
For measurement of mutual inductance we can use
(a) Anderson bridge
(b) Maxwell’s bridge
(c) Heaviside bridge
(d) Any of the above
Ans: c
For measurement of inductance having high value, we should use
(a) Maxwell’s bridge
(b) Maxwell Wein bridge
(c) Hay’s bridge
(d) Any of the above
Ans: c
If the current in a capacitor leads the voltage by 80°, the loss angle of the capacitor is
(a) 10°
(b) 80°
(c) 120°
(d) 170°
Ans: a
In a Schering bridge the potential of the detector above earth potential is
(a) a few volts only
(6) 1 kV
(c) 5 kV
(d) 10 kV
Ans: a
To avoid the effect of stray magnetic field in A.C. bridges we can use
(a) magnetic screening
(b) Wagner earthing device
(c) wave filters
(d) any of the above
Ans: a
If an inductance is connected in one arm of bridge and resistances in the remaining three arms
(a) the bridge can always be balanced
(b) the bridge cannot be balanced
(c) the bridge can be balanced if the resistances have some specific values
Ans: b
A power factor meter has
(a) one current circuit and two pressure circuits
(b) one current circuit and one pressure circuit
(c) two current circuits and one pres¬sure circuit
(d) none of the above
Ans: a
The two pressure coils of a single phase power factor meter have
(a) the same dimensions and the same number of turns
(b) the same dimension but different number of turns
(c) the same number of turns but different dimensions
(d) none of the above
Ans: a
In a single phase power factor meter the phase difference between the currents in the two pressure coils is
(a) exactly 0°
(b) approximately 0°
(c) exactly 90°
(d) approximately 90°
Ans: c
In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at
(a) 0°
(b) 60°
(c) 90°
(d) 120°
Ans: d
In a vibrating reed frequency meter the natural frequencies of two adjacent reeds have a difference of
(a) 0.1 Hz
(b) 0.25 Hz
(c) 0.5 Hz
(d) 1.5 Hz
Ans: c
In a Weston frequency meter, the magnetic axes of the two fixed coils are
(a) parallel
(b) perpendicular
(c) inclined at 60°
(d) inclined at 120°
Ans: b
A Weston frequency meter is
(a) moving coil instrument
(b) moving iron instrument
(c) dynamometer instrument
(d) none of the above
Ans: b
A Weston synchronoscope is a
(a) moving coil instrument
(b) moving iron instrument
(c) dynamometer instrument
(d) none of the above
Ans: c
In a Weston synchronoscope, the fixed coils are connected across
(a) bus-bars
(b) incoming alternator
(c) a lamp
(d) none of the above
Ans: b
In Weston synchronoscope the moving coil is connected across
(a) bus-bars
(b) incoming alternator
(c) fixed coils
(d) any of the above
Ans: a
The power factor of a single phase load can be calculated if the instruments available are
(a) one voltmeter and one ammeter
(b) one voltmeter, one ammeter and one wattmeter
(c) one voltmeter, one ammeter and one energy meter
(d) any of the above
Ans: b
The desirable static characteristics of a measuring system are
(a) accuracy and reproducibility
(b) accuracy, sensitivity and reproducibility
(c) drift and dead zone
(d) static error
Ans: b
The ratio of maximum displacement deviation to full scale deviation of the instrument is called
(a) static sensitivity
(b) dynamic deviation
(c) linearity
(d) precision or accuracy
Ans: c
Systematic errors are
(a) instrumental errors
(b) environmental errors
(c) observational errors
(d) all of the above
Ans: d
Standard resistor is made from
(a) platinum
(b) maganin
(c) silver
(d) nichrome
Ans: b
Commonly used standard capacitor is
(a) spherical type
(b) concentric cylindrical type
(c) electrostatic type
(d) multilayer parallel plate type
Ans: b
Operating torques in analogue instruments are
(a) deflecting and control
(b) deflecting and damping
(c) deflecting, control and damping
(d) vibration and balancing
Ans: c
Commonly used instruments in power system measurement are
(a) induction
(b) moving coil or iron
(c) rectifier
(d) electrostatic
Ans: a
Damping of the Ballistic galvanometer is made small to
(a) get first deflection large
(b) make the system oscillatory
(c) make the system critically damped
(d) get minimum overshoot
Ans: a
If an instrument has cramped scale for larger values, then it follows
(a) square law
(b) logarithmic law
(c) uniform law
(d) none of the above
Ans: b
Volt box is a component to
(a) extend voltage range
(6) measure voltage
(c) compare voltage in a box
(d) none of the above
Ans: a
E.m.f. of a Weston cell is accurately measured by
(a) electrostatic voltmeter
(b) hot wire voltmeter
(c) isothermal voltmeter
(d) electrodynamic voltmeter
Ans: a
The gravity controlled instrument has crowded scale because current is proportional to
(a) balancing weight
(b) deflection angle
(c) sine of deflection angle
Ans: c
A sensitive galvanometer produces large deflection for a
(a) small value of current
(b) large value of current
(c) large value of power
(d) large value of voltage
(e) none of the above
Ans: a
A multirangq instrument has
(a) multiple shunt or series resistances inside the meter
(b) multicoii arrangement
(c) variable turns of coil
(d) multi range meters inside the measurement system
(e) any of the above
Ans: a
The rectifier instrument is not free from
(a) temperature error
(b) wave shape error
(c) frequency error
(d) all of the above
Ans: c
Alternating current is measured by
(a) induction ammeter
(b) permanent magnet type ammeter
(c) electrostatic ammeter
(d) moving iron repulsion type voltmeter
Ans: a
Most sensitive galvanometer is
(a) elastic galvanometer
(b) vibration galvanometer
(c) Duddlb galvanometer
(d) spot ballistic galvanometer
Ans: d
Instrument transformers are
(a) potential transformers
(b) current transformers
(c) both (a) and (b)
(d) power transformers
Ans: c
An instrument transformer is used to extend the range of
(a) induction instrument
(b) electrostatic instrument
(c) moving coil instrument
(d) any of the above
Ans: a
Wattmeter cannot be designed on the principle of
(a) electrostatic instrument
(b) thermocouple instrument
(c) moving iron instrument
(d) electrodynamic instrument
Ans: c
In an energy meter braking torque is produced to
(a) safe guard it against creep
(b) brake the instrument
(c) bring energy meter to stand still
(d) maintain steady speed and equal to driving torque
Ans: d
Various adjustments in an energy meter include
(a) light load or friction
(b) lag and creep
(c) overload and voltage compensation
(d) temperature compensation
(e) all of the above
Ans: e
The power of a n-phase circuit can be measured by using a minimum of
(a) (n – 1) wattmeter elements
(b) n wattmeter elements
(c) (n + 1) wattmeter elements
(d) 2n wattmeter elements
Ans: a
Two holes in the disc of energy meter are drilled at the opposite sides of the spindle to
(a) improve its ventilation
(b) eliminate creeping at no load
(c) increase its deflecting torque
(d) increase its braking torque
Ans: b
Which of the following is measured by using a vector voltmeter ?
(a) Amplifier gain and phase shift
(b) Filler transfer functions
(c) Complex insersion loss
(d) All of the above
Ans: d
The principle on which vector voltmeter is based is
(a) that it works on the principle of complex variation
(b) that it measures the response of linear ramp voltage
(c) same as digital meter
(d) that it measures the amplitude of a single at two points and at the same time measures their phase difference
Ans: d
To measure radio frequency, the suitable frequency meter is
(a) Weston frequency meter
(b) reed vibrator frequency meter
(c) heterodoxy frequency meter
(d) electrical resonance frequency meter
Ans: c

Control Systems

In an open loop control system
(a) Output is independent of control input
(b) Output is dependent on control input
(c) Only system parameters have effect on the control output
(d) None of the above
Ans: a
For open control system which of the following statements is incorrect ?
(a) Less expensive
(b) Recalibration is not required for maintaining the required quality of the output
(c) Construction is simple and maintenance easy
(d) Errors are caused by disturbances
Ans: b
A control system in which the control action is somehow dependent on the output is known as
(a) Closed loop system
(b) Semiclosed loop system
(c) Open system
(d) None of the above
Ans: a
In closed loop control system, with positive value of feedback gain the overall gain of the system will
(a) decrease
(b) increase
(c) be unaffected
(d) any of the above
Ans: a
Which of the following is an open loop control system ?
(a) Field controlled D.C. motor
(b) Ward leonard control
(c) Metadyne
(d) Stroboscope
Ans: a
Which of the following statements is not necessarily correct for open control system ?
(a) Input command is the sole factor responsible for providing the control action
(b) Presence of non-linearities causes malfunctioning
(c) Less expensive
(d) Generally free from problems of non-linearities
Ans: b
In open loop system
(a) the control action depends on the size of the system
(b) the control action depends on system variables
(c) the control action depends on the input signal
(d) the control action is independent of the output
Ans: d
has tendency to oscillate.
(a) Open loop system
(b) Closed loop system
(c) Both (a) and (b)
(d) Neither (a) nor (b)
Ans: b
A good control system has all the following features except
(a) good stability
(b) slow response
(c) good accuracy
(d) sufficient power handling capacity
Ans: b
A car is raining at a constant speed of 50 km/h, which of the following is the feedback element for the driver ?
(a) Clutch
(b) Eyes
(c) Needle of the speedometer
(d) Steering wheel
(e) None of the above
Ans: c
The initial response when tne output is not equal to input is called
(a) Transient response
(b) Error response
(c) Dynamic response
(d) Either of the above
Ans: a
A control system working under unknown random actions is called
(a) computer control system
(b) digital data system
(c) stochastic control system
(d) adaptive control system
Ans: c
An automatic toaster is a ______ loop control system.
(a) open
(b) closed
(c) partially closed
(d) any of the above
Ans: a
Any externally introduced signal affecting the controlled output is called a
(a) feedback
(b) stimulus
(c) signal
(d) gain control
Ans: b
A closed loop system is distinguished from open loop system by which of the following ?
(a) Servomechanism
(b) Feedback
(c) Output pattern
(d) Input pattern
Ans: b

16 is a part of the human temperature control system.
(a) Digestive system
(b) Perspiration system
(c) Ear
(d) Leg movement
Ans: b

By which of the following the control action is determined when a man walks along a path ?
(a) Brain
(b) Hands
(c) Legs
(d) Eyes
Ans: d

18 is a closed loop system.
(a) Auto-pilot for an aircraft
(6) Direct current generator
(c) Car starter
(d) Electric switch
Ans: a

Which of the following devices are commonly used as error detectors in instruments ?
(a) Vernistats
(b) Microsyns
(c) Resolvers
(d) Any of the above
Ans: d
Which of the following should be done to make an unstable system stable ?
(a) The gain of the system should be decreased
(b) The gain of the system should be increased
(c) The number of poles to the loop transfer function should be increased
(d) The number of zeros to the loop transfer function should be increased
Ans: b

21 increases the steady state accuracy.
(a) Integrator
(b) Differentiator
(c) Phase lead compensator
(d) Phase lag compensator
Ans: a

A.C. servomotor resembles
(a) two phase induction motor
(b) Three phase induction motor
(c) direct current series motor
(d) universal motor
Ans: a
As a result of introduction of negative feedback which of the following will not decrease ?
(a) Band width
(b) Overall gain
(c) Distortion
(d) Instability
Ans: a
Regenerative feedback implies feedback with
(a) oscillations
(b) step input
(c) negative sign
(d) positive sign
Ans: d
The output of a feedback control system must be a function of
(a) reference and output
(b) reference and input
(e) input and feedback signal
(d) output and feedback signal
Ans: a

26 is an open loop control system.
(a) Ward Leonard control
(b) Field controlled D.C. motor
(c) Stroboscope
(d) Metadyne
Ans: b

A control system with excessive noise, is likely to suffer from
(a) saturation in amplifying stages
(b) loss of gain
(c) vibrations
(d) oscillations
Ans: a
Zero initial condition for a system means
(a) input reference signal is zero
(b) zero stored energy
(c) ne initial movement of moving parts
(d) system is at rest and no energy is stored in any of its components
Ans: d
Transfer function of a system is used to calculate which of the following ?
(a) The order of the system
(b) The time constant
(c) The output for any given input
(d) The steady state gain
Ans: c
The band width, in a feedback amplifier.
(a) remains unaffected
(b) decreases by the same amount as the gain increase
(c) increases by the sane saaaajajt as the gain decrease
(d) decreases by the same amount as the gain decrease
Ans: c
On which of the following factors does the sensitivity of a closed loop system to gain changes and
load disturbances depend ?
(a) Frequency
(b) Loop gain
(c) Forward gain
(d) All of the above
Ans: d
The transient response, with feedback system,
(a) rises slowly
(b) rises quickly
(c) decays slowly
(d) decays quickly
Ans: d
The second derivative input signals modify which of the following ?
(a) The time constant of the system
(b) Damping of the system
(c) The gain of the system
(d) The time constant and suppress the oscillations
(e) None of the above
Ans: d
Which of the following statements is correct for any closed loop system ?
(a) All the co-efficients can have zero value
(6) All the co-efficients are always non-zero
(c) Only one of the static error co-efficients has a finite non-zero value
(d) None of the above
Ans: c
Which of the following statements is correct for a system with gain margin close to unity or a phase margin close to zero ?
(a) The system is relatively stable
(b) The system is highly stable
(c) The system is highly oscillatory
(d) None of the above
Ans: c
Due to which of the following reasons excessive bond width in control systems should be avoided ?
(a) It leads to slow speed of response
(b) It leads to low relative stability
(c) Noise is proportional to band width
(d) None of the above
Ans: c
In a stable control system backlash can cause which of the following ?
(a) Underdamping
(b) Overdamping
(c) Poor stability at reduced values of open loop gain
(d) Low-level oscillations
Ans: d
In an automatic control system which of the following elements is not used ?
(a) Error detector
(b) Final control element
(c) Sensor
(d) Oscillator
Ans: d
In a control system the output of the controller is given to
(a) final control element
(b) amplifier
(c) comparator
(d) sensor
(e) none of the above
Ans: a
A controller, essentially, is a
(a) sensor
(b) clipper
(c) comparator
(d) amplifier
Ans: c
Which of the following is the input to a controller ?
(a) Servo signal
(b) Desired variable value
(c) Error signal
(d) Sensed signal
Ans:
The on-off controller is a _____ system.
(a) digital
(b) linear
(c) non-linear
(d) discontinuous
Ans:
The capacitance, in force-current analogy, is analogous to
(a) momentum
(b) velocity
(c) displacement
(d) mass
Ans: d
The temperature, under thermal and electrical system analogy, is considered analogous to
(a) voltage
(b) current
(c) capacitance
(d) charge
(e) none of the above
Ans: a
In electrical-pneumatic system analogy the current is considered analogous to
(a) velocity
(b) pressure
(c) air flow
(d) air flow rate
Ans: d
In liquid level and electrical system analogy, voltage is considered analogous to
(a) head
(b) liquid flow
(c) liquid flow rate
(d) none of the above
Ans: a
The viscous friction co-efficient, in force-voltage analogy, is analogous to
(a) charge
(b) resistance
(c) reciprocal of inductance
(d) reciprocal of conductance
(e) none of the above
Ans: b
In force-voltage analogy, velocity is analogous to
(a) current
(b) charge
(c) inductance
(d) capacitance
Ans: a
In thermal-electrical analogy charge is considered analogous to
(a) heat flow
(b) reciprocal of heat flow
(c) reciprocal of temperature
(d) temperature
(e) none of the above
Ans: d
Mass, in force-voltage analogy, is analogous to
(a) charge
(b) current
(c) inductance
(d) resistance
Ans: c
The transient response of a system is mainly due to
(a) inertia forces
(b) internal forces
(c) stored energy
(d) friction
Ans: c

52 signal will become zero when the feedback signal and reference signs are equal.
(a) Input
(b) Actuating
(c) Feedback
(d) Reference
Ans: b

A signal other than the reference input that tends to affect the value of controlled variable is known
as
(a) disturbance
(b) command
(c) control element
(d) reference input
Ans: a
The transfer function is applicable to which of the following ?
(a) Linear and time-in variant systems
(b) Linear and time-variant systems
(c) Linear systems
(d) Non-linear systems
(e) None of the above
Ans: a
From which of the following transfer function can be obtained ?
(a) Signal flow graph
(b) Analogous table
(c) Output-input ratio
(d) Standard block system
(e) None of the above
Ans: a

56 is the reference input minus the primary feedback.
(a) Manipulated variable
(b) Zero sequence
(c) Actuating signal
(d) Primary feedback
Ans: c

The term backlash is associated with
(a) servomotors
(b) induction relays
(c) gear trains
(d) any of the above
Ans:
With feedback _____ increases.
(a) system stability
(b) sensitivity
(c) gain
(d) effects of disturbing signals
Ans: a
By which of the following the system response can be tested better ?
(a) Ramp input signal
(b) Sinusoidal input signal
(c) Unit impulse input signal
(d) Exponentially decaying signal
Ans: c
In a system zero initial condition means that
(a) The system is at rest and no energy is stored in any of its components
(b) The system is working with zero stored energy
(c) The system is working with zero reference signal
Ans: a
In a system low friction co-efficient facilitates
(a) reduced velocity lag error
(b) increased velocity lag error
(c) increased speed of response
(d) reduced time constant of the system
Ans: a
Hydraulic torque transmission system is analog of
(a) amplidyneset
(b) resistance-capacitance parallel circuit
(c) motor-generator set
(d) any of the above
Ans:
Spring constant in force-voltage analogy is analogous to
(a) capacitance
(b) reciprocal of capacitance
(c) current
(d) resistance
Ans: b
The frequency and time domain are related through which of the following?
(a) Laplace Transform and Fourier Integral
(b) Laplace Transform
(c) Fourier Integral
(d) Either (b) or (c)
Ans: a
An increase in gain, in most systems, leads to
(a) smaller damping ratio
(b) larger damping ratio
(c) constant damping ratio
(d) none of the above
Ans: a
Static error coefficients are used as a measure of the effectiveness of closed loop systems for
specified ________ input signal.
(a) acceleration
(b) velocity
(c) position
(d) all of the above
Ans: d
A conditionally stable system exhibits poor stability at
(a) low frequencies
(b) reduced values of open loop gain
(c) increased values of open loop gain
(d) none of the above
Ans: b
The type 0 system has ______ at the origin.
(a) no pole
(b) net pole
(c) simple pole
(d) two poles
(e) none of the above
Ans: a
The type 1 system has ______ at the origin.
(a) no pole
(b) net pole
(c) simple pole
(d) two poles
Ans: c
The type 2 system has ______ at the origin.
(a) no net pole
(b) net pole
(c) simple pole
(d) two poles
Ans: d
The position and velocity errors of a type-2 system are
(a) constant, constant
(b) constant, infinity
(c) zero, constant
(d) zero, zero
Ans: c
Velocity error constant of a system is measured when the input to the system is unit _______ function.
(a) parabolic
(b) ramp
(c) impulse
(d) step
Ans: b
In case of type-1 system steady state acceleration is
(a) unity
(b) infinity
(c) zero
(d) 10
Ans: b
If a step function is applied to the input of a system and the output remains below a certain level for all the time, the system is
(a) not necessarily stable
(b) stable
(c) unstable
(d) always unstable
(e) any of the above
Ans: a
Which of the following is the best method for determining the stability and transient response ?
(a) Root locus
(b) Bode plot
(c) Nyquist plot
(d) None of the above
Ans: a
Phase margin of a system is used to specify which of the following ?
(a) Frequency response
(b) Absolute stability
(c) Relative stability
(d) Time response
Ans: c
Addition of zeros in transfer function causes which of the following ?
(a) Lead-compensation
(b) Lag-compensation
(c) Lead-lag compensation
(d) None of the above
Ans: b
technique is not applicable to nonlinear system ?
(a) Nyquist Criterion
(b) Quasi linearization
(c) Functional analysis
(d) Phase-plane representation
Ans: a
In order to increase the damping of a badly underdamped system which of following compensators may be used ?
(a) Phase-lead
(b) Phase-lag
(c) Both (a) and (b)
(d) Either (a) and (b)
(e) None of the above
Ans: a
The phase lag produced by transportation relays
(a) is independent of frequency
(b) is inverseh’proportional to frequency
(c) increases linearly with frequency
(d) decreases linearly with frequency
Ans: c
In a stable control system saturation can cause which of the following ?
(a) Low-level oscillations
(b) High-level oscillations
(c) Conditional stability
(d) Overdamping
Ans:
Which of the following can be measured by the use of a tachogenerator ?
(a) Acceleration
(b) Speed
(c) Speed and acceleration
(d) Displacement
(e) None of the above
Ans: b

83 is not a final control element.
(a) Control valve
(b) Potentiometer
(c) Electropneumatic converter
(d) Servomotor
Ans: b

Which of the following is the definition of proportional band of a controller ?
(a) The range of air output as measured variable varies from maximum to minimum
(b) The range of measured variables from set value
(c) The range of measured variables through which the air output changes from maximum to minimum
(d) Any of the above
(e) None of the above
Ans: c
In pneumatic control systems the control valve used as final control element converts
(a) pressure signal to electric signal
(b) pressure signal to position change
(c) electric signal to pressure signal
(d) position change to pressure signal
(e) none of the above
Ans: b
Pressure error can be measured by which of the following ?
(a) Differential bellows and straingauge
(b) Selsyn
(c) Strain gauge
(d) Strain gauge and potentiometer
Ans: a
Which of the following devices is used for conversion of co-ordinates ?
(a) Microsyn
(b) Selsyn
(c) Synchro-resolver
(d) Synchro-transformer
Ans: c
The effect of error damping is to
(a) provide larger settling lime
(b) delay the response
(c) reduce steady state error
(d) any of the above
(e) none of the above
Ans: c

89 technique gives quick transient and stability response
(a) Root locus
(b) Bode
(c) Nyquist
(d) Nichols
Ans: a

A phase lag lead network introduces in the output
(a) lag at all frequencies
(b) lag at high frequencies and lead at low frequencies
(c) lag at low frequencies and lead at high frequencies
(d) none of the above
Ans: c
Which of the following is the non-linearity caused by servomotor ?
(a) Static friction
(b) Backlash
(c) Saturation
(d) None of the above
Ans: c

92 can be extended to systems which are time-varying ?
(a) Bode-Nyquist stability methods
(b) Transfer functions
(c) Root locus design
(d) State model representatives
Ans: d

When the initial conditions of a system are specified to be zero it implies that the system is
(a) at rest without any energy stored in it
(b) working normally with reference input
(c) working normally with zero reference input
(d) at rest but stores energy
Ans: d
Which of the following is an electromagnetically device ?
(a) Induction relay
(b) Thermocouple
(c) LVDT
(d) Any of the above
(e) None of the above
Ans: c
A differentiator is usually not a part of a control system because it
(a) reduces damping
(b) reduces the gain margin
(c) increases input noise
(d) increases error
Ans: c
If the gain of the critical damped system is increased it will behave as
(a) oscillatory
(b) critically damped
(c) overdamped
(d) underdamped
(e) none of the above
Ans: d
In a control system integral error compensation _______ steady state error
(a) increases
(b) minimizes
(c) does not have any effect on
(d) any of the above
Ans: b
With feed back _____ reduces.
(a) system stability
(6) system gain
(c) system stability and gain
(d) none of the above
Ans: b
An amplidyne can give which of the following characteristics ?
(a) Constant current
(b) Constant voltage
(c) Constant current as well as constant voltage
(d) Constant current, constant voltage and constant power
(e) None of the above
Ans: d
Which of the following can be measured by LVDT?
(a) Displacement
(b) Velocity
(c) Acceleration
(d) Any of the above
Ans: d

101 directly converts temperature into voltage.
(a) Thermocouple
(b) Potentiometer
(c) Gear train
(d) LVDT
(e) None of the above
Ans: a

The transfer function technique is considered as inadequate under which of the following
conditions ?
(a) Systems having complexities and non-linearities
(b) Systems having stability problems
(c) Systems having multiple input disturbances
(d) All of the above
Ans: d
Which of the following is the output of a thermocouple ?
(a) Alternating current
(b) Direct current
(c) A.C. voltage
(d) D.C. voltage
(e) None of the above
Ans: d
A.C. servomotor is basically a
(a) universal motor
(b) single phase induction motor
(c) two phase induction motor
(d) three phase induction motor
Ans: c
The first order control system, which is well designed, has a
(a) small bandwidth
(b) negative time constant
(c) large negative transfer function pole
(d) none of the above
Ans: c
Which of the following is exhibited by Root locus diagrams ?
(a) The poles of the transfer function for a set of parameter values
(b) The bandwidth of the system
(c) The response of a system to a step input
(d) The frequency response of a system
(e) None of the above
Ans: a

Electric Traction

Which of the following is an advantage of electric traction over other methods of traction ?
(a) Faster acceleration
(b) No pollution problems
(c) Better braking action
(d) All of the above
Ans: a
Which of the following is the voltage for single phase A.C. system ?
(a) 22 V
(b) 440 V
(c) 5 kV
(d) 15 kV
(e) None of the above
Ans: a
Long distance railways use which of the following ?
(a) 200 V D.C.
(b) 25 kV single phase A.C.
(c) 25 kV two phase A.C.
(d) 25 kV three phase A.C.
Ans: b
The speed of a locomotive is controlled by
(a) flywheel
(b) gear box
(c) applying brakes 11.
(d) regulating steam flow to engine
Ans:
Main traction systems used in India are, those using
(a) electric locomotives
(b) diesel engine locomotives
(c) steam engine locomotives
(d) diesel electric locomotives
(e) all of the above
Ans: e

6, in India diesel locomotives are manufactured at
(a) Ajmer
(b) Varanasi
(c) Bangalore
(d) Jamalpur
Ans: b

For diesel locomotives the range of horsepower is
(a) 50 to 200
(b) 500 to 1000
(c) 1500 to 2500
(d) 3000 to 5000
Ans: c
_______ locomotive has the highest operational availability.
(a) Electric
(b) Diesel
(c) Steam
Ans: a
The horsepower of steam locomotives is
(a) up to 1500
(b) 1500 to 2000
(c) 2000 to 3000
(d) 3000 to 4000
Ans: a
The overall efficiency of steam locomotive is around
(a) 5 to 10 percent
(b) 15 to 20 percent
(c) 25 to 35 percent
(d) 35 to 45 percent
Ans: a
In tramways which of the following motors is used ?
(a) D.C. shunt motor
(b) D.C. series motor
(c) A.C. three phase motor
(d) AC. single phase capacitor start motor
Ans: b
In a steam locomotive electric power is provided through
(a) overhead wire
(b) battery system
(c) small turbo-generator
(d) diesel engine generator
Ans: c
Which of the following drives is suitable for mines where explosive gas exists ?
(a) Steam engine
(b) Diesel engine
(c) Battery locomotive
(d) Any of the above
Ans: c
In case of locomotives the tractive power is provided by
(a) single cylinder double acting steam engine
(b) double cylinder, single acting steam engine
(c) double cylinder, double acting steam engine
(d) single stage steam turbine
Ans: c
Overload capacity of diesel engines is usually restricted to
(a) 2 percent
(b) 10 percent
(c) 20 percent
(d) 40 percent
Ans: a
In case of steam engines the steam pressure is
(a) 1 to 4 kgf/cm2
(b) 5 to 8 kgf/cm2
(c) 10 to 15 kgf/cm2
(d) 25 to 35 kgf/cm2
Ans: c

17.. The steam engine provided on steam locomotives is
(a) single acting condensing type
(b) single acting non-condensing type
(e) double acting condensing type
(d) double acting non-condensing type
Ans: b

Electric locomotives in India are manufactured at
(a) Jamalpur
(b) Bangalore
(c) Chittranjan
(d) Gorakhpur
Ans: c
The wheels of a train, engine as well as bogies, are slightly tapered to
(a) reduce friction
(b) increase friction
(c) facilitate braking
(d) facilitate in taking turns
Ans: d
Automatic signalling is used for which of the following trains ?
(a) Mail and express trains
(b) Superfast trains
(c) Suburban and Urban electric trains
(d) All trains
Ans: b
The efficiency of diesel locomotives is nearly
(a) 20 to 25 percent
(b) 30 to 40 percent
(c) 45 to 55 percent
(d) 60 to 70 percent
Ans: a
The speed of a superfast train is
(a) 60 kmph
(b) 75 kmph
(c) 100 kmph
(d) more than 100 kmph
Ans: d
The number of passenger coaches that can be attached to a diesel engine locomotive on broad gauge is usually restricted to
(a) 5
(b) 10
(c) 14
(d) 17
Ans: b
Which of the following state capitals is not on broad gauge track ?
(a) Lucknow
(b) Bhopal
(c) Jaipur
(d) Chandigarh
Ans: c
Which of the following is the advantage of electric braking ?
(a) It avoids wear of track
(b) Motor continues to remain loaded during braking
(c) It is instantaneous
(d) More heat is generated during braking
Ans: a

Which of the following braking systems on the locomotives is costly ?
(a) Regenerative braking on electric locomotives
(b) Vacuum braking on diesel locomotives
(c) Vacuum braking on steam locomotives
(d) All braking systems are equally costly
Ans: a

Tractive effort is required to
(a) overcome the gravity component of train mass
(b) overcome friction, windage and curve resistance
(c) accelerate the train mass
(d) do all of the above
Ans: d
For given maximum axle load tractive efforts of AC. locomotive will be
(a) less than that of D.C. locomotive
(b) more than that of D.C. locomotive
(c) equal to that of D.C. locomotive
(d) none of the above
Ans: b
Co-efficient of adhesion reduces due to the presence of which of the following ?
(a) Sand on rails
(b) Dew on rails
(c) Oil on the rails
(d) both (b) and (c)
Ans: d
Due to which of the following co-efficient of adhesion improves ?
(a) Rust on the rails
(b) Dust on the rails
(c) Sand on the rails
(d) All of the above
Ans: d
Quadrilateral speed-time curve pertains to which of the following services ?
(a) Main line service
(b) Urban service
(c) Sub-urban service
(d) Urban and sub-urban service
Ans: d
Which of the following is the disadvantage of electric traction over other systems of traction ?
(a) Corrosion problems in the under-ground pipe work
(b) Short time power failure interrupts traffic for hours
(c) High capital outlay in fixed installations beside route limitation
(d) Interference with communication lines
(c) All of the above
Ans: c
Co-efficient of adhesion is
(a) high in case of D.C. traction than in the case of AC. traction
(b) low in case of D.C. traction than in the case of AC. traction
(c) equal in both AC. and D.C. traction
(d) any of the above
Ans: b
Speed-time curve of main line service differs from those of urban and suburban services on following account
(a) it has longer free running period
(b) it has longer coasting period
(c) accelerating and braking periods are comparatively smaller
(d) all of the above
Ans: d
The rate of acceleration on suburban orurban services is restricted by the consideration of
(a) Engine power
(b) Track curves
(c) Passenger Discomfort
(d) Track size
Ans: c
The specific energy consumption of a train depends on which of the following ?
(a) Acceleration and retardation
(b) Gradient
(c) Distance covered
(d) All of the above
Ans: d
The friction at the track is proportional to
(a) 1/speed
(b) l/(speed)2
(c) speed
(d) none of the above
Ans: c
The air resistance to the movement of the train is proportional to
(a) speed
(b) (speed)
(c) (speed)
(d) 1/speed
Ans: b
The normal value of adhesion friction is
(a) 0.12
(b) 0.25
(c) 0.40
(d) 0.75
Ans: b
The pulsating torque exerted by steam locomotives causes which of the following?
(a) Jolting and skidding
(b) Hammer blow
(c) Pitching
(d) All of the above
Ans: a
Which of the following braking systems is used on steam locomotives ?
(a) Hydraulic system
(b) Pneumatic system
(c) Vacuum system
(d) None of the above
Ans: c
Vacuum is created by which of the following?
(a) Vacuum pump
(b) Ejector
(c) Any of the above
(d) None of the above
Ans: c
The resistance encountered by a train in motion is on account of
(a) resistance offered by air
(b) friction at the track
(c) friction at various parts of the rolling stock
(d) all of the above
Ans: d
Battery operated trucks are used in
(a) steel mills
(b) power stations
(c) narrow gauge traction
(d) factories for material transportation
Ans: d

45 method can bring the locomotive to dead stop.
(a) Plugging braking
(b) Rheostatic braking
(c) Regenerative braking
(d) None of the above
Ans: a

The value of co-efficient of adhesion will be high when rails are
(a) greased
(b) wet
(c) sprayed with oil
(d) cleaned with sand
Ans: d
The voltage used for suburban trains in D.C. system is usually
(a) 12 V
(b) 24 V
(c) 220 V
(d) 600 to 750 V
Ans: d
For three-phase induction motors which of the following is the least efficient method of speed control ?
(a) Cascade control
(b) Pole changing
(c) Rheostat control
(d) Combination of cascade and pole changing
Ans: c
Specific energy consumption becomes
(a) more on steeper gradient
(b) more with high train resistance
(c) less if distance between stops is more
(d) all of the above
Ans: d
In main line service as compared to urban and suburban service
(a) distance between the stops is more
(b) maximum speed reached is high
(c) acceleration and retardation rates are low
(d) all of the above
Ans: d
Locomotive having monomotor bogies
(a) has better coefficient of adhesion
(b) are suited both for passanger as well as freight service
(c) has better riding qualities due to the reduction of lateral forces
(d) has all above qualities
Ans: d
Series motor is not suited for traction duty due to which of the following account ?
(a) Less current drain on the heavy load torque
(b) Current surges after temporary switching off supply
(c) Self relieving property
(d) Commutating property at heavy load
Ans: b
When a bogie negotiates a curve, reduction in adhesion occurs resulting in sliding. Thus sliding is acute when
(a) wheel base of axles is more
(b) degree of curvature is more
(c) both (a) and (b)
(d) none of the above
Ans: c
Energy consumption in propelling the train is required for which of the following?
(a) Work against the resistance to motion
(b) Work against gravity while moving up the gradient
(c) Acceleration
(d) All of the above
Ans: d
An ideal traction system should have
(a) easy speed control
(b) high starting tractive effort
(c) equipment capable of with standing large temporary loads
(d) all of the above
Ans: d

56 have maximum unbalanced forces
(a) Diesel shunters
(b) Steam locomotives
(c) Electric locomotives
(d) Diesel locomotives
Ans: b

Specific energy consumption is affected by which of the following factors ?
(a) Retardation and acceleration values
(b) Gradient
(c) Distance between stops
(d) All of the above
Ans: d
In case of ________ free running and coasting periods are generally long.
(a) main-line service
(b) urban service
(c) sub-urban service
(d) all of the above
Ans: a
Overhead lines for power supply to tramcars are at a minimum height of
(a) 3 m
(b) 6 m
(c) 10 m
(d) 15 m
Ans: c
The return circuit for tramcars is through
(a) neutral wire
(b) rails
(c) cables
(d) common earthing
Ans: b
Specific energy consumption is least in _______ service.
(a) main line
(b) urban
(c) suburban
Ans: a
Locomotives with monometer bogies have
(a) uneven distribution of tractive effect
(b) suitability for passanger as well as freight service
(c) lot of skidding
(d) low co-efficient of adhesion
Ans: b

63 _______ was the first city in India to adopt electric traction.
(a) Delhi
(b) Madras
(c) Calcutta
(d) Bombay
Ans: d

64 _______ frequency is not common in low frequency traction system
(a) 40 Hz
(b) 25 Hz
(c) 16 Hz
Ans: a

For 25 kV single phase system power supply frequency is
(a) 60 Hz
(b) 50 Hz
(c) 25 Hz
(d) 16 Hz
Ans: b
Power for lighting in passanger coach, in a long distance electric train, is provided
(a) directly through overhead electric line
(b) through individual generator of bogie and batteries
(c) through rails
(d) through locomotive
Ans: b
In India, electrification of railway track was done for the first time in which of the following years ?
(a) 1820—1825
(b) 1880—1885
(c) 1925—1932
(d) 1947—1954
Ans: c
Suri transmission is
(a) electrical-pneumatic
(b) mechanical-electrical
(c) hydro-mechanical
(d) hydro-pneumatic
Ans: c
In case of a steam engine an average coal consumption per km is nearly
(a) 150 to 175 kg
(b) 100 to 120 kg
(c) 60 to 80 kg
(d) 28 to 30 kg
Ans: d
Which of the following happens in Kando system ?
(a) Three phase A.C. is converted into D.C.
(b) Single phase A.C. is converted into D.C.
(c) Single phase supply is converted into three phase system
(d) None of the above
Ans: c
For which of the following locomotives the maintenance requirements are the least?
(a) Steam locomotives
(b) Diesel locomotives
(c) Electric locomotives
(d) Equal in all of the above
Ans: b
Which of the following methods is used to control speed of 25 kV, 50 Hz single phase traction ?
(a) Reduced current method
(b) Tap changing control of transformer
(c) Series parallel operation of motors
(d) All of the above
Ans: b
If the co-efficient of adhesion on dry rails is 0.26, which of the following could be the value for wet rails ?
(a) 0.3
(b) 0.26
(c) 0.225
(d) 0.16
Ans: d

74 watt-hours per tonne km is usually the specific energy consumption for suburban services.
(a) 15—20
(b) 50—75
(c) 120—150
(d) 160—200
Ans: b

The braking retardation is usually in the range
(a) 0.15 to 0.30 km phps
(b) 0.30 to 0.6 km phps
(c) 0.6 to 2.4 km phps
(d) 3 to 5 km phps
(e) 10 to 15 km phps
Ans: d
The rate of acceleration on suburban orurban service is in the range
(a) 0.2 to 0.5 km phps
(b) 1.6 to 4.0 km phps
(c) 5 to 10 km phps
(d) 15 to 25 km phps
Ans: b
The coasting retardation is around
(a) 0.16 km phps
(b) 1.6 km phps
(c) 16 km phps
(d) 40 km phps
Ans: a

Industrial Drives

The selection of an electric motor for any application depends on which of the following factors ?
(a)    Electrical characteristics
(b)    Mechanical characteristics
(c)    Size and rating of motors
(d)    Cost
(e)    All of the above
Answer: e
For a particular application the type of electric-and control gear are determined by which of the following considerations ?
(a)    Starting torque
(b)    Conditions of environment
(c)    Limitation on starting current
(d)    Speed control range and its nature
(e)    All of the above
Answer: e
Which of the following motors is preferred for traction work ?
(a)     Universal motor
(b)     D.C. series motor
(c)    Synchronous motor
(d)    Three-phase induction motor
Answer: c

4   Which of the following motors always starts on load ?
(a)     Conveyor motor
(b)     Floor mill motor
(c)    Fan motor
(d)    All of the above
Answer: d

is preferred for automatic drives.
(a)     Squirrel cage induction motor
(b)     Synchronous motors
(c)    Ward-Leonard controlled D.C. motors
(d)    Any of the above
Answer: c
When the load is above _____ a synchronous motor is found to be more economical.
(a)     2 kW
(b)     20 kW
(c)     50 kW
(d)     100 kW
Answer: d
The load cycle for a motor driving a power press will be
(a)     variable load
(b)     continuous
(c)    continuous but periodical
(d)    intermittent and variable load
Answer: d
Light duty cranes are used in which of the following ?
(a)     Power houses
(b)     Pumping stations
(c)    Automobile workshops
(d)    All of the above
Answer: d
While selecting an electric motor for a floor mill, which electrical characteristics will be of least significance ?
(a)    Running characteristics
(b)    Starting characteristics
(c)    Efficiency
(d)    Braking
Answer: d
Which of the following motors are pre-ferred for overhead travelling cranes ?
(a)    Slow speed motors
(b)    Continuous duty motors
(c)    Short time rated motors
(d)    None of the above
Answer: c
is preferred for synthetic fibre mills.
(a)     Synchronous motor
(b)     Reluctance motor
(c)    Series motor
(d)    Shunt motor
Answer: b
Ward-Leonard controlled D.C. drives are generally used for ______ excavators.
(a)     Light duty
(b)     Medium duty
(c)    Heavy duty
(d)    All of the above
Answer: c
Which of the following motors is used for elevators ?
(a)    Induction motor
(b)    Synchronous motor
(c)    Capacitor start single phase motor
(d)    Any of the above
Answer: a
Which part of a motor needs maximum attention for maintenance ?
(a)     Frame
(b)     Rearing
(c)    Stator winding
(d)    Rotor winding
Answer: b
need frequent starting and stopping of electric motors,
(a)     Paper mills
(b)     Grinding mills
(c)    Air-conditioners
(d)    Lifts and hoists
Answer: d
Which feature, while selecting a.motor for centrifugal pump, will be of least significance ?
(a)    Starting characteristics
(b)    Operating speed
(c)    Horse power
(d)    Speed control
Answer: d
_______ motor is a constant speed motor.
(a)    Synchronous motor
(b)    Schrage motor
(c)    Induction motor
(d)    Universal motor
Answer: a
The starting torque in case of centrifugal pumps is generally
(a)    less than running torque
(b)    same as running torque
(c)    slightly more than running torque
(d)    double the running torque
Answer: a
Which of the following motors are best for the rolling mills ?
(a)     Single phase motors
(b)     Squirrel cage induction motors
(c)    Slip ring induction motors
(d)    D.C. motors
Answer: d
is not a part of ball bearing ?
(a)    Inner race
(b)    Outer race
(c)    Cage
(d)    Bush
Answer: d
The starting torque of a D.C. motor is independent of which of the following?
(a)     Flux
(b)     Armature current
(c)     Flux and armature current
(d)    Speed
Answer: d
Rotor of a motor is usually supported on _______ bearings.
(a)     ball or roller
(b)     needle
(c)     bush
(d)     thrust
Answer: a
For which of the following applications D.C. motors are still preferred ?
(a)     High efficiency operation
(b)     Reversibility
(c)    Variable speed drive
(d)    High starting torque
Answer: c
In a paper mill where constant speed is required
(a)     synchronous motors are preferred
(b)     A.C. motors are preferred
(c)    individual drive is preferred
(d)    group drive is preferred
Answer: c
A reluctance motor
(a)    is provided with slip rings
(b)    requires starting gear
(c)    has high cost
(d)    is compact
Answer: d
The size of an excavator is usually expressed in terms of
(a)     ‘crowd’ motion
(b)     angle of swing
(c)    cubic metres
(d)    travel in metres
Answer: c
For blowers which of the following motor is preferred ?
(a)     D.C. series motor
(b)     D.C. shunt motor
(c)    Squirrel cage induction motor
(d)    Wound rotor induction motor
Answer: b
Belted slip ring induction motor is almost invariably used for
(a)     water pumps
(b)     jaw crushers
(c)    centrifugal blowers
(d)    none of the above
Answer: b
Which of the following is essentially needed while selecting a motor ?
(a)     Pulley
(b)     Starter
(c)    Foundation pedal
(d)    Bearings
Answer: b
Reluctance motor is a
(a)     variable torque motor
(b)     low torque variable speed motor
(c)    self starting type synchronous motor
(d)    low noise, slow speed motor
Answer: c
method of starting a three phase induction motor needs six terminals.
(a)    Star-delta
(b)    Resistance starting
(c)    Auto-transformer
(d)    None of the above
Answer: a
In ______ method of staging three phase induction motors the starting voltage is not reduced.
(a)    auto-transformer
(b)    star-delta
(c)    slip ring
(d)    any of the above
Answer: c
In jaw crushers a motor has to often start against ______ load.
(a) heavy
(b) medium
(c) normal
(d) low
Answer: a
For a motor-generator set which of the following motors will be preferred ?
(a)     Synchronous motor
(b)     Slip ring induction motor
(c)    Pole changing induction motor
(d)    Squirrel cage induction motor
Answer: a
Which of the following motors is usually preferred for kiln drives ?
(a)     Cascade controlled A.C. motor
(b)     Slip ring induction motor
(c)    Three phase shunt wound com-mutator motor
(d)    Any of the above
Answer: d
Heat control switches are used in
(a)    transformers
(b)    cooling ranges
(c)    three phase induction motors
(d)    single phase
Answer: b
has relatively wider range of speed control.
(a)     Synchronous motor
(6)     Ship ring induction motor
(c)    Squirrel cage induction motor
(d)    D.C. shunt motor
Answer: d
In squirrel cage induction motors which of the following methods of starting cannot be used ?
(a)     Resistance in rotor circuit
(b)     Resistance in stator circuit
(c)     Auto-transformer starting
(d)     Star-delta starting
Answer: a
In which of the following applications the load on motor changes in cyclic order ?
(a)     Electric shovels
(b)     Cranes
(c)     Rolling mills
(d)     All of the above
Answer: d
Flame proof motors are used in
(a)     paper mills
(b)     steel mills
(c)    moist atmospheres
(d)    explosive atmospheres
Answer: d
Which of the following machines has heavy fluctuation of load ?
(a) Printing machine
(b) Punching machine
(c) Planer
(d) Lathe
Answer: b
For derries and winches which of the following drives can be used ?
(a)    Pole changing squirrel cage motors
(b)    D.C. motors with Ward-leonard con-trol
(c)    A.C. slip ring motors with variable resistance
(d)    Any of the above
Answer: d
Battery operated scooter for braking uses
(a)     plugging
(b)     mechanical braking
(c)    regenerative braking
(d)    rheostatic braking
Answer: b
has least range of speed control.
(a)    Slip ring induction motor
(b)    Synchronous motor
(c)    D.C. shunt motor
(d)    Schrage motor
Answer: b
has the least value of starting torque to full load torque ratio.
(a)    D.C. shunt motor
(b)    D.C. series motor
(c)    Squirrel cage induction motor
(d)     Slip ring induction motor
Answer: c
In case of _______ speed control by injecting e.m.f. in the rotor circuit is possible,
(a)     d.c. shunt motor
(b)     schrage motor
(c)    synchronous motor
(d)    slip ring induction motor
Answer: d
A pony motor is used for the starting which of the following motors ?
(a)     Squirel cage induction motor
(b)     Schrage motor
(c)    Synchronous motor
(d)    None of the above
Answer: c
In ________ the speed can be varied by changing the position of brushes.
(a)     slip ring motor
(b)     schrage motor
(c)    induction motor
(d)    repulsion motor
Answer: b
In which of the following applications variable speed operation is preferred ?
(a)     Exhaust fan
(b)     Ceiling fan
(c)     Refrigerator
(d)     Water pump
Answer: b
Heavy duty cranes are used in
(a)    ore handling plants
(b)    steel plants
(c)    heavy engineering workshops
(d)    all of the above
Answer: d
The travelling speed of cranes varies from
(a)     20 to 30 m/s
(b)     10 to 15 m/s
(c)     5 to 10 m/s
(d)     1 to 2.5 m/s
Answer: d
Besides a constant speed a synchronous rotor possesses which of the following advantages ?
(a)     Lower cost
(b)     Better efficiency
(c)     High power factor
(d)     All of the above
Answer: c
By the use of which of the following m D.C. can be obtained from AC. ?
(a)    Silicon diodes
(b)    Mercury arc rectifier
(c)    Motor generator set
(d)    Any of the above
Answer: d
Which of the following motors is preferred when quick speed reversal is the main consideration ?
(a)     Squirrel cage induction motor
(b)     Wound rotor induction motor
(e)    Synchronous motor
(d)     D.C. motor
Answer: d
Which of the following motors is preferred when smooth and precise speed control over a wide range is desired ?
(a)     D.C. motor
(b)     Squirrel cage induction motor
(c)     Wound rotor induction motor
(d)     Synchronous motor
Answer: a
For crane travel which of the following motors is normally used ?
(a)     Synchronous motor
(b)     D.C. differentially compound motor
(c)    Ward-Leonard controlled D.C. shunt motor
(d)    AC. slip ring motor
Answer: d
The capacity of a crane is expressed in terms of
(a)     type of drive
(b)     span
(c)     tonnes
(d)     any of the above
Answer: c
The characteristics of drive for crane hoisting and lowering are which of the following ?
(a)     Precise control
(b)     Smooth movement
(c)    Fast speed control
(d)    All of the above
Answer: d
Which of the following motors is preferred for boom hoist of a travelling crane ?
(a)     Single phase motor
(b)     Synchronous motor
(c)    A.C. slip ring motor
(d)    Ward-Leonard controlled D.C. shunt motor
Answer: c
A wound rotor induction motor is preferred, as compared to squirrel cage induction motor, when major consideration is
(a)    slop speed operation
(b)    high starting torque
(c)    low windage losses
(d)    all of the above
Answer: b
Which of the following motors has series characteristics ?
(a)     Shaded pole motor
(b)     Repulsion motor
(c)    Capacitor start motor
(d)    None of the above
Answer: b
Which of the following happens when star-delta starter is used ?
(a)    Starting voltage is reduced
(b)    Starting current is reduced
(c)    Both (a) and (b)
(d)    None of the above
Answer: c
For a D.C. shunt motor which of the following is incorrect ?
(a)     Unsuitable for heavy duty starting
(b)     Torque varies as armature current
(c)    Torque-armature current is a straight line
(d)    Torque is zero for zero armature current
Answer: a
For which of the following applications motor has to start with high acceleration?
(a)    Oil expeller
(b)    Floor mill
(c)    Lifts and hoists
(d)    Centrifugal pump
Answer: c
Which of the following types of motor enclosure is safest ?
(a)    Totally enclosed
(b)    Totally enclosed fan cooled
(c)    Open type
(d)    Semi closed
Answer: b
While selecting motor for an air conditioner which of the following characteristics is of great importance ?
(a)     Type of bearings
(b)     Type of enclosure
(c)    Noise
(d)    Arrangement for power transmis¬sion
(e)    None of the above
Answer: c
The diameter of the rotor shaft for an electric motor depends on which of the following ?
(a)     r.p.m. only
(b)     Horse power only
(c)    Horse power and r.p.m.
(d)    Horse power, r.p.m. and power factor
Answer: c
Which of the following alternatives will be cheaper ?
(a)     A 100 H.P. AC. three phase motor
(b)     Four motors of 25 H.P. each
(c)    Five motors of 20 H.P. each
(d)    Ten motors of 10 H.P. each
Answer: a
The cost of an induction motor will increase as
(a)    horsepower rating increases but r.p.m. decreases
(b)    horsepower rating decreases but r.p.m. increases
(c)    horsepower rating and operating speed increases
(d)    horsepower rating and operating speed decreases
Answer: a
In series motor which of the following methods can be used for changing the flux per pole ?
(a)    Tapped field control
(b)    Diverter field control
(c)    Series-parallel control
(d)    Any of the above
Answer: d

Heating & Welding

Which of the following is an advantage of heating by electricity ?
(a)     Quicker operation
(b)     Higher efficiency
(c)    Absence of flue gases
(d)    All of the above
Ans: d
________ has the highest value of thermal conductivity.
(a) Copper
(b) Aluminium
(c) Brass
(d) Steel
Ans: a
Which of the following heating methods has maximum power factor ?
(a)    Arc heating
(b)    Dielectric heating
(c)    Induction heating
(d)    Resistance heating
Ans: d
method has leading power factor
(a)     Resistance heating
(b)     Dielectric heating
(c)    Arc heating
(d)    Induction heating
Ans: b
is used for heating non-conducting materials.
(a)     Eddy current heating
(b)     Arc heating
(c)    Induction heating
(d)    Dielectric heating
Ans: d
Which of the following methods of heating is not dependent on the frequency of supply ?
(a)     Induction heating
(b)     Dielectric heating
(c)    Electric resistance heating
(d)    All of the above
Ans: c
When a body reflects entire radiation incident on it, then it is known as
(a)     white body
(b)     grey body
(c)    black body
(d)    transparent body
Ans: a
For the transmission of heat from one body to another
(a)     temperature of the two bodies must be different
(b)     both bodies must be solids
(c)    both bodies must be in contact
(d)    at least one of the bodies must have some source of heating
Ans: a
Heat transfer by condition will not occur when
(a)     bodies are kept in vacuum
(b)     bodies are immersed in water
(c)    bodies are exposed to thermal radiations
(d)    temperatures of the two bodies are identical
Ans: d
A perfect black body is one that
(a)     transmits all incident radiations
(b)     absorbs all incident radiations
(c)    reflects all incident radiations
(d)    absorbs, reflects and transmits all incident radiations
Ans: b
Heat is transferred simultaneously by condition, convection and radiation
(a)     inside boiler furnaces
(b)     during melting of ice
(c)    through the surface of the insulted pipe carrying steam
(d)    from refrigerator coils to freezer of a refrigerator
Ans: a
The process of heat transfer during the reentry of satellites and missiles, at very high speeds, into earth’s atmosphere is known as
(a)     ablation
(b)     radiation
(c)    viscous dissipation
(d)    irradiation
Ans: a
Which of the following has the highest value of thermal conductivity ?
(a)     Water
(b)     Steam
(c)     Solid ice
(d)     Melting ice
Ans: c
Induction heating process is based on which of the following principles ?
(a)     Thermal ion release principle
(b)     Nucleate heating principle
(c)    Resistance heating principle
(d)    Electro-magnetic induction princi¬ple
Ans: d
Which of the following insulating materials was suitable for low temperature applications ?
(a)     Asbestos paper
(b)     Diatomaceous earth
(c)    80 percent magnesia
(d)     Cork
Ans: b
A non-dimensional number generally associated with natural convection heat transfer is
(a)     Prandtl number
(b)     Grashoff number
(c)     Pecelet number
(d)     Nusselt number
Ans: b
The temperature inside a furnace is usually measured by which of the following ?
(a)    Optical pyrometer
(b)    Mercury thermometer
(c)    Alcohol thermometer
(d)    Any of the above
Ans: a
Which of the following will happen if the thickness of refractory wall of furnace is increased ?
(a)     Heat loss through furnace wall will increase
(b)     Temperature inside the furnace will fall
(c)    Temperature on the outer surface of furnace walls will drop
(d)    Energy consumption will increase
Ans: c
The material of the heating element for a furnace should have
(a)     lower melting point
(b)     higher temperature coefficient
(c)     high specific resistance
(d)     all of the above
Ans: c
In a resistance furnace the atmosphere is
(a)     oxidizing
(b)     deoxidising
(c)     reducing
(d)     neutral
Ans: a
By which of the following methods the temperature inside arc nace can be varied ?
(a)    By disconnecting some of the heating elements
(b)    By varying the operating voltage
(c)    By varying the current through heating elements
(d)    By any of the above method
Ans: d
In induction heating ______ is abnormally high.
(a)     phase angle
(b)     frequency
(c)    current
(d)     voltage
Ans: b
By the use of which of the following, high frequency power supply for induction furnaces can be obtained ?
(a)     Coreless transformers
(b)     Current transformers
(c)    Motor-generator set
(d)    Multi-phase transformer
Ans: c
Induction furnaces are employed for which of the following ?
(a)     Heat treatment of castings
(b)     Heating of insulators
(c)    Melting aluminium
(d)    None of the above
Ans: a
In an electric room heat convector the method of heating used is
(a)     arc heating
(b)     resistance heating
(c)    induction heating
(d)    dielectric heating
Ans: b
In a domestic cake baking oven the temperature is controlled by
(a)     voltage variation
(b)     thermostat
(c)    auto-transformer
(d)    series-parallel operation
Ans: d
In an electric press mica is used
(a)     as an insulator
(b)     as a device for power factor improvement
(c)    for dielectric heating
(d)    for induction heating
Ans: a
Induction heating takes place it which of the following ?
(a)     Insulating materials
(b)     Conducting materials which are magnetic
(c)    Conducting materials which are non-magnetic
(d)    Conducting materials which may or may not be magnetic
Ans: d
For heating element high resistivity material is chosen to
(a)    reduce the length of heating element
(b)    increase the life of the heating element
(c)    reduce the effect of oxidation
(d)     produce large amount of heat
Ans: a
In resistance heating highest working temperature is obtained from heating elements made of
(a)     nickel copper
(b)     nichrome
(c)    silicon carbide
(d)     silver
Ans: c
For intermittent work which of the following furnaces is suitable ?
(a)    Indirect arc furnace
(b)    Core less furnace
(c)    Either of the above
(d)     None of the above
Ans: a
Due to which of the following reasons it is desirable to have short arc length ?
(a)     To achieve better heating
(b)     To increase the life of roof refractory
(c)    To have better stirring action
(d)    To reduce problem of oxidation
(e)    All of the above
Ans: e
In the indirect resistance heating method, maximum heat-transfer takes place by
(a) radiation
(b) convection
(c) conduction
(d) any of the above
Ans: a
Properly of low temperature co-eflficient of heating element is desired due to which of the following reasons ?
(a)     To avoid initial rush of current
(b)     To avoid change in kW rating with temperature
(c)    Both (a) and (b)
(d)    Either (a) or (b)
Ans: c
Which of the following methods is used to control temperature in resistance furnaces ?
(a)    Variation of resistance
(b)    Variation of voltage
(c)    Periodical switching on and off of the supply
(d)    All of the above methods
Ans: d
It is desirable to operate the arc furnaces at power factor of
(a)     zero
(b)     0.707 lagging
(c)     unity
(d)     0.707 leading
Ans: b
Radiations from a black body are proportional to
(a)    T1
(b)    T2
(c)    T3
(d)    T*
Ans: d
In arc furnace the function of choke is
(a)    to stabilize the arc
(b)    to imprpve, power factor
(c)    to reduce severity of the surge
(d)    none of the above
Ans: a
Ajax Wyatt furnace is started when
(a)     it is filled below core level
(b)     it is filled above core level
(c)    it is fully empty
(d)    none of the above
Ans: b
In electric press, mica is used because it is _______ conductor of heat but/and    ________ conductor of electricity.
(a)     bad, good
(b)     bad, bad
(c)     good, bad
(d)     good, good
Ans:
Resistance variation method of temperature control is done by connecting resistance elements in
(a)     series
(b)     parallel
(c)    series-parallel connections
(d)    star-delta connections
(e)    all of the above ways
Ans: e
Hysteresis loss and eddy current loss are used in
(a)    induction heating of steel
(b)    dielectric heating
(c)    induction heating of brass
(d)    resistance heating
Ans: a
In heating the ferromagnetic material by induction heating, heat is produced due to
(a)     induced current flow through the charge
(b)     hysteresis loss taking place below curie temperature
(c)    due to hysteresis loss as well as eddy current loss takingplace in the charge
(d)    none of the above factors
Ans: c
Radiant heating is used for which of the following ?
(a)     Annealing of metals
(b)     Melting of ferrous metals
(c)    Heating of liquids in electric kettle
(d)    Drying of paints and varnishes
Ans: d
Which of the following devices is necessarily required for automatic temperature control in a furnace ?
(a)     Thermostat
(b)     Thermocouple
(c)    Auto-transformer
(d)    Heating elements of variable resis-tance material
Ans: b
For radiant heating around 2250°C, the heating elements are made of
(a)     copper alloy
(b)     carbon
(c)    tungsten alloy
(d)    stainless steel alloy
Ans: c
Which of the following is an advantage of eddy current heating ?
(a)    The amount of heat generated can be controlled accurately
(b)    Heat at very high rate can be gene-rated
(c)    The area of the surface over which heat is produced can be accurately controlled
(d)    All of the above
Ans: d
The electrode of a direct arc furnace is made of
(a)     tungsten
(b)     graphite
(c)     silver
(d)     copper
Ans: b
Direct arc furnaces have which of the following power factors ?
(a)     Unity
(b)     Low, lagging
(c)     Low, leading
(d)     Any of the above
Ans: b
In direct arc furnace, which of the following has high value ?
(a)    Current
(b)    Voltage
(c)    Power factor
(d)    All of the above
Ans: a

Digital Electronics

1.In which of the following base systems is 123 not a valid number?
(a) Base 10
(b) Base 16
(c)Base8
(d) Base 3
Ans:d

Storage of 1 KB means the following number of bytes
(a) 1000
(b)964
(c)1024
(d) 1064
Ans:c
What is the octal equivalent of the binary number:
10111101
(a)675
(b)275
(c) 572
(d) 573.
Ans:b
Pick out the CORRECT statement:
(a) In a positional number system, each symbol represents the same value irrespective of its position
(b) The highest symbol in a position number system as a value equal to the number of symbols in the system
(c) It is not always possible to find the exact binary
(d) Each hexadecimal digit can be represented as a sequence of three binary symbols.
Ans:c

5.The binary code of (21.125)10 is
(a) 10101.001
(b) 10100.001
(c) 10101.010
(d) 10100.111.
Ans:a

6.A NAND gate is called a universal logic element because
(a) it is used by everybody
(b) any logic function can be realized by NAND gates alone
(c) all the minization techniques are applicable for optimum NAND gate realization
(d) many digital computers use NAND gates.
Ans:b

Digital computers are more widely used as compared to analog computers, because they are
(a) less expensive
(b) always more accurate and faster
(c) useful over wider ranges of problem types
(d) easier to maintain.
Ans:c
Most of the digital computers do not have floating point hardware because
(a) floating point hardware is costly
(b) it is slower than software
(c) it is not possible to perform floating point addition by hardware
(d) of no specific reason.
Ans:a
The number 1000 would appear just immediately after
(a) FFFF (hex)
(b) 1111 (binary)
(c) 7777 (octal)
(d) All of the above.
Ans:d
(1(10101)2 is
(a) (37)10
(b) ( 69)10
(c) (41 )10
(d) — (5)10
Ans:a
The number of Boolean functions that can be generated by n variables is equal to
(a) 2n
(b) 22 n
(c) 2n-1
(d) — 2n
Ans:b
Consider the representation of six-bit numbers by two’s complement, one’s complement, or by sign and magnitude: In which representation is there overflow from the addition of the integers 011000 and 011000?
(a) Two’s complement only
(b) Sign and magnitude and one’s complement only
(c) Two’s complement and one’s complement only
(d) All three representations.
Ans:d
A hexadecimal odometer displays F 52 F. The next reading will be
(a)F52E
(b)G52F
(c)F53F
(d)F53O.
Ans:d
Positive logic in a logic circuit is one in which
(a) logic 0 and 1 are represented by 0 and positive voltage respectively
(b) logic 0 and, -1 are represented by negative and positive voltages respectively
(c) logic 0 voltage level is higher than logic 1 voltage level
(d) logic 0 voltage level is lower than logic 1 voltage level.
Ans:d
Which of the following gate is a two-level logic gate
(a) OR gate
(b) NAND gate
(c) EXCLUSIVE OR gate
(d) NOT gate.
Ans:c
Among the logic families, the family which can be used at very high frequency greater than 100 MHz in a 4 bit synchronous counter is
(a) TTLAS
(b) CMOS
(c)ECL
(d)TTLLS
Ans:c
An AND gate will function as OR if
(a) all the inputs to the gates are “1”
(b) all the inputs are ‘0’
(c) either of the inputs is “1”
(d) all the inputs and outputs are complemented.
Ans:d
An OR gate has 6 inputs. The number of input words in its truth table are
(a)6
(b)32
(c) 64
(d) 128
Ans:c
A debouncing circuit is
(a) an astable MV
(b) a bistable MV
(c) a latch
(d) a monostable MV.
Ans:c
NAND. gates are preferred over others because these
(a) have lower fabrication area
(b) can be used to make any gate
(c) consume least electronic power
(d) provide maximum density in a chip.
Ans:b
In case of OR gate, no matter what the number of inputs, a
(a) 1 at any input causes the output to be at logic 1
(b) 1 at any input causes the output to be at logic 0
(c) 0 any input causes the output to be at logic 0
(d) 0 at any input causes the output to be at logic 1.
Ans:a
The fan put of a 7400 NAND gate is
(a)2TTL
(b)5TTL
(c)8TTL
(d)10TTL
Ans:d
Excess-3 code is known as
(a) Weighted code
(b) Cyclic redundancy code
(c) Self-complementing code
(d) Algebraic code.

Ans:c

Assuming 8 bits for data, 1 bit for parity, I start bit and 2 stop bits, the number of characters that 1200 BPS communication line can transmit is
(a)10 CPS
(b)120 CPS
(c) 12CPS
(d) None of the above.
Ans:c
Indicate which of the following three binary additions are correct?
1.1011 + 1010 = 10101
II. 1010 + 1101 = 10111
III. 1010 + 1101 = 11111
(a) I and II
(b) II and III
(c) III only
(d) II and III
Ans:d
Which is the correct order of sequence for representing the input values in K-map?
a. (00, 01, 10, 11)
b. (00, 10, 01, 11)
c. (00, 01, 11, 10)
d. (00, 10, 11, 01)

ANSWER:a

The binary number 10101 is equivalent to decimal number …………..

a.19
b.12
c.27
d.21
Answer : d

The universal gate is ………………

a.NAND gate
b.OR gate
c.AND gate
d.None of the above
Answer : a

The inverter is ……………

a.NOT gate
b.OR gate
c.AND gate
d.None of the above
Answer : a

The inputs of a NAND gate are connected together. The resulting circuit is ………….

a.OR gate
b.AND gate
c.NOT gate
d.None of the above
Answer : c

The NOR gate is OR gate followed by ………………

a.AND gate
b.NAND gate
c.NOT gate
d.None of the above
Answer : c

The NAND gate is AND gate followed by …………………

a.NOT gate
b.OR gate
c.AND gate
d.None of the above
Answer : a

Digital circuit can be made by the repeated use of ………………

a.OR gates
b.NOT gates
c.NAND gates
d.None of the above
Answer : c

The only function of NOT gate is to ……………..

a.Stop signal
b.Invert input signal
c.Act as a universal gate
d.None of the above
Answer : b

When an input signal 1 is applied to a NOT gate, the output is ………………

a.0
b.1
c.Either 0 & 1
d.None of the above
Answer : a

In Boolean algebra, the bar sign (-) indicates ………………..

a.OR operation
b.AND operation
c.NOT operation
d.None of the above
Answer : c

What would happen, if smaller logic modules are utilized for performing logical functions associated with FPGA?
Propagation delay will increase
B. FPGA area will increase
C. Wastage of logic modules will not be prevented
D. Number of interconnected paths in device will decrease
a. A & B
b. C & D
c. A & D
d. B & C

ANSWER:a

What is/are the configurable functions of each and every IOBs connected around the FPGA device from the operational point of view?
a. Input operation
b. Tristate output operation
c. Bi-directional I/O pin access
d. All of the above
ANSWER:d
Which type of CPLD packaging can provide maximum number of pins on the package due to small size of the pins?
a. PLCC
b. QFP
c. PGA
d. BGA
ANSWER:d
Which mechanism allocates the binary value to the states in order to reduce the cost of the combinational circuits?
a. State Reduction
b. State Minimization
c. State Assignment
d. State Evaluation
ANSWER:c

Circuit Theorems and Conversions

Some circuits require more than one voltage or current source.
True
B. False

Answer :- A

An ideal voltage source has zero internal resistance.
True
B. False

Answer :- A

A practical current source has a finite internal resistance.
True
B. False

Answer :- A

Norton’s equivalent current (IN) is an open-circuit current between two points in a circuit.
True
B. False

Answer :- B

A practical voltage source has a nonzero internal resistance.
True
B. False

Answer :- A

You cannot convert a voltage source to an equivalent current source, or vice versa.
True
B. False

Answer :- B

An ideal current source has zero internal resistance.
True
B. False

Answer :- B

The Thevenin equivalent voltage (VTH) is the short-circuit voltage between two terminals in a circuit.
True
B. False

Answer :- B

Transistors act basically as voltage sources.
True
B. False

Answer :- B

Conversions between delta-type and wye-type circuit arrangements are useful in certain specialized applications.
True
B. False

Answer :- A

OPAMP Circuits:

A non inverting closed loop op amp circuit generally has a gain factor
A. Less than one
B. Greater than one
C. Of zero
D. Equal to one

Answer :- B. For non inverting amplifier the gain is A = 1 + (Rf/Rin)). So it will be always more than one

If ground is applied to the (+) terminal of an inverting op-amp, the (–) terminal will
A. Not need an input resistor
B. Be virtual ground
C. Have high reverse current
D. Not invert the signal

Answer :- B. Other options are not suitable.

The closed-loop voltage gain of an inverting amplifier equal to
A. The ratio of the input resistance to feedback resistance
B. The open-loop voltage gain
C. The feedback resistance divided by the input resistance
D. The input resistance

Answer :- C

When a number of stages are connected in parallel, the overall gain is the product of the individual stage gains
A. True
B. False

Answer :- B

An ideal OP-AMP is an ideal
a) Current controlled Current source
b) Current controlled voltage source
c) Voltage controlled voltage source
d) voltage controlled current source

Answer :- C. The ideal Opamp output voltage is maintained constant. It is controlled by input voltage.

The ideal OP-AMP has the following characteristics.
a) Ri=∞ ,A=∞ ,R0=0
b) Ri=0 ,A=∞ ,R0=0
c) Ri=∞ ,A=∞ ,R0=∞
d) Ri=0 ,A=∞ ,R0=∞

Answer :- A.

Calculate the cutoff frequency of a first-order low-pass filter for R1 = 2.5kΩ and C1 = 0.05μF
A. 1.273kHz
B. 12.73kHz
C. 127.3 kHz
D. 127.3 Hz

Answer :- A.
Hint: low pass filter cut off frequency f = 1/(2πRC)

How many op-amps are required to implement this equation
2
B. 3
C. 4
D. 1

Answer :-D. The output voltage of inverting amplifier is Vout = (-Rf/Rin)Vin. By keeping 1 inverting amplifier and three no of sources (V1, V2, V3) in series corresponding input resistors(R1, R2, R3), we can get this equation.

How many op-amps are required to implement this equation Vo = V1
A. 4
B. 3
C. 2
D. 1

Answer :- D. The voltage follower which has one opamp has the output of Vo = Vin

An OPAMP has a slew rate of 5 V/μ S .The largest sine wave O/P voltage possible at a frequency of 1 MHZ is
A. 10 volts
B. 5 volts
C. 5/ volts
D. 5/2 volts

Answer :- D
Hint: Slew rate is defined as the max. rate of change of output voltage. Its unit is V/μS.
Time period = 1/f = 1/1MHz = 1μS
V= Vm. sin(ωt) = Vm. sin(2πf.t)
slew rate = dV/dt = d(Vm. sin(2πf.t)/ dt=Vm. 2πf. cost…

11) An ideal OP-AMP is an ideal
A. Current controlled Current source
B. Current controlled Voltage source
C. Voltage controlled Voltage source
D. Voltage controlled Current source

Answer :- C

12) A 741-Type OP-AMP has a gain-bandwith product of 1MHz. A non-inverting amplifier using this opamp & having a voltage gain of 20db will exhibit -3db bandwidth of
A. 50KHz
B. 100KHz
C. 1000/17KHz
D. 1000/7.07KHz

Answer :- A

13) An amplifier using an opamp with slew rate SR=1v/sec has a gain of 40db.If this amplifier has to faithfully amplify sinusoidal signals from dc to 20KHz without introducing any slew-rate induced distortion, then the input signal level exceed
A. 795mV
B. 395mV
C. 795mV
D. 39.5mV

Answer :- C

14) The ideal OP-AMP has the following characteristics
A. Ri=∞,A=∞,R0=0
B. Ri=0,A=∞,R0=0
C. Ri=∞,A=∞,R0=∞
D. Ri=0,A=∞,R0=∞

Answer :- A

15) The approximate input impedance of the opamp circuit which has Ri=10k, Rf=100k, RL=10k
A. ∞
B. 120k
C. 110k
D. 10k

Answer :- C

16) An opamp has a slew rate of 5V/ S. the largest sine wave o/p voltage possible at a frequency of 1MHz is
A. 10 V
B. 5 V
C. 5V
D. 5/2 V

Answer :- A

17) Assume that the op-amp of the fig. is ideal. If Vi is a triangular wave, then V0 will be
A. Square wave
B. Triangular wave
C. Parabolic wave
D. Sine wave

Answer :- D

18) A differential amplifier is invariably used in the i/p stage of all op-amps. This is done basically to provide the op-amps with a very high
A. CMMR
B. Bandwidth
C. Slew rate
D. Open-loop gain

Answer :- C

19) A differential amplifier has a differential gain of 20,000. CMMR=80dB. The common mode gain is given by
A. 2
B. 1
C. 1/2
D. 0

Answer :- A

20) In the differential voltage gain & the common mode voltage gain of a differential amplifier are 48db & 2db respectively, then its common mode rejection ratio is
A. 23dB
B. 25dB
C. 46dB
D. 50dB

Answer :- C

21) Which of the following amplifier is used in a digital to analog converter?
(a) Non inverter
(b) Voltage follower
(c) Summer
(d) Difference amplifier

Answer :- C

22) Differential amplifiers are used in
(a) Instrumentation amplifiers
(b) Voltage followers
(c) Voltage regulators
(d) Buffers

Answer :-A

23) For an ideal op-amp, which of the following is true?
(a) The differential voltage across the input terminals is zero
(b) The current into the input terminals is zero
(c) The current from output terminal is zero
(d) The output resistance is zero

Answer :- C

24) The two input terminals of an opamp are labeled as
a) High and low
b) Positive and negative
c) Inverting and non inverting
d) Differential ans non differential

Answer :-C

25) When a step-input is given to an op-amp integrator, the output will be
(a) A ramp.
(b) A sinusoidal wave.
(c) A rectangular wave.
(d) A triangular wave with dc bias

Answer :- A

26) For an op-amp having differential gain Av and common-mode gain Ac the CMRR is given by
A. Av + Ac
B. Av / Ac
C. 1 + Av / Ac)
D. Ac / Av

Answer :-B

27) Hysteresis is desirable in Schmitt-trigger, because
A. Energy is to be stored/discharged in parasitic capacitances.
B. Effects of temperature would be compensated.
C. Devices in the circuit should be allowed time for saturation and desaturation.
D. It would prevent noise from causing false triggering.

Answer :- C

28) The output voltage Vo of the above circuit is
(a) -6V
(b) -5V
(c) -1.2V
(d) -0.2V
Answer :- B

29) In the above circuit the current ix is
(a) 0.6A
(b) 0.5A
(c) 0.2A
(d) 1/12A
Answer :- B

30) Op-amp circuits may be cascaded without changing their input output relationships
(a) True
(b) False
Answer :- A

ANALOG ELECTRONICS

The early effect in a bipolar junction transistor is caused by
A. fast turn-on
B.fast turn-off
C. large collector-base reverse bias
D. large emitter-base forward bias
MOSFET can be used as a
A. current controlled capacitor
B. voltage controlled capacitor
C. current controlled inductor
D. voltage controlled inductors
Thermal runaway is not possible in FET because as the temperature of FET increases
A. the mobility decreases
B. the transconductance increases
C. the drain current increases
D. none of the above
A source follower using an FET usually has a voltage gain which is
A. greater than +100
B. slightly less than unity but positive
C. exactly unity but negative
D. about -10
A differential amplifier has a differential gain of 20,000 . CMRR=80 dB. The common mode
gain is given by
A. 2
B. 1
C. 1/2
D. 0
The approximate input impedance of the OPAMP circuit which has
Ri=10k,Rf=100k,RL=10k
A. ∞
B.120k
C.110k
D.10k
An OPAMP has a slew rate of 5 V/µ S .The largest sine wave O/P voltage possible at a
frequency of 1MHZ is
voltsA. 10
voltsB. 5 volts C. 5/
voltsD.5/2
A change in the value of the emitter resistance Re in a differential amplifier
A. affects the difference mode gain Ad
B. affects the common mode gain Ac
C.affects both Ad and Ac
D. does not effect either Ad and Ac
OBJECTIVE QUESTIONS IN ANALOG ELECTRONICS
A differential amplifier is invariably used in the i/p stage of all OP-AMPs.This is dome
basically to provide the OP-AMPs with a very high
A.CMRR
B.bandwidth
C. slew rate
D.open-loop gain
The effective channel length of a MOSFET in a saturation decreases with increase in
A. gate voltage
B.drain voltage
C.source voltage
D.body voltage
Which of the following is not associated with a p-n junction
A. junction capacitance
B.charge storage capacitance
C.depletion capacitance
D.channel length modulation
In a p-n junction diode under reverse bias , the magnitude of electric field is maximum at
A. the edge of the depletion region on the p-side
B. the edge of the depletion region on the n-side
C. the p-n junction
D. the center of the depletion region on the n-side
An n- channel JFET has IDSS=2mA,and Vp=-4v.Its transconductance gm=in mA/V)for an
applied gate to source voltage VGS=-2v is
A.0.25
B.0.5
C.0.75
D.1
In a common emitter, unbypassed resister provides
A.voltage shunt feedback
B.current series feedback
C.negative voltage feedback
D.positive current feedback
A constant current signal across a parallel RLC circuits gives an o/p of 1.4v at the signal
frequency of 3.89KHZ and 4.1KHZ .At the frequency of 4KHZ,the o/p voltage will be
A.1 v
B. 2v
C.1.4v
D.2.8v
Class AB operation is often used in power large signal) amplifiers in order to
A. get maximum efficiency
B.remove even harmonics
C. overcome a crossover distortion
D.reducing collector dissipation
The bandwidth of an RF tuned amplifier is dependent on
A. Q –factor of the tuned o/p circuit
B. Q –factor of the tuned i/p circuit
C. Quiescent operating point
D. Q-factor of the o/p and i/p circuits as well as quiescent operating point
If =0.98 ,Ico=6µA and Iβ=100µA for a transistor,then the value of Ic will be
A.2.3mA
B.3.2mA
C.4.6 mA
D.5.2mA

19.The MOSFET switch in its on-state may be considered equivalent to
A.resistor
B.inductor
C.capacitor
D.battery

Most of the linear ICs are based on the two-transistor differential amplifier because of its
A. input voltage dependent linear transfer characteristic
B. high voltage gain
C. high input resistance
D. high CMRR
Negative feedback in an amplifier
A. Reduces gain
B. Increase frequency &phase distortion
C. Reduces bandwidth
D. Increases noise
A dc power supply has no-load voltage of 30v,and a full-load voltage of 25v at full-load
current of 1A.Its output resistance & load regulation ,respectively are
A. 5 Ω & 20 %
B. 25 Ω & 20 %
C. 5 Ω & 16.7 %
D. 25 Ω & 16.7 %
The current gain of a bipolar transistor drops at high frequencies because of
A. Transistor capacitances
B. High current effects in the base
C. Parasitic inductive elements
D. The early effect
The ideal OP-AMP has the following characteristics.
A. Ri=∞ ,A=∞ ,R0=0
B. Ri=0 ,A=∞ ,R0=0
C. Ri=∞ ,A=∞ ,R0=∞
D. Ri=0 ,A=∞ ,R0=∞
An npn BJT has gm=38mA/v, cµ =10¯14 F, cπ =10¯13F and DC current gain β0=90.For this
transistor fT & fβ are
A. fT =1.64 x 108 Hz & fβ = 1.47 x 1010 Hz.
B. fT =1.47 x 1010 Hz & fβ = 1.64 x 108 Hz
C. fT =1.33 x 1012 Hz & fβ = 1.47 x 1010 Hz
D. fT =1.47 x 1010 Hz & fβ = 1.33 x 1012 Hz
A 741-type OP-AMP has a gain-bandwidth product of 1MHz.A non-inverting amplifier
using this opamp & having a voltage gain of 20db will exhibit -3db bandwidth of
A. 50 KHz
B. 100KHz
C. 1000/17 KHz
D. 1000/7.07 KHz

27.An amplifier using an opamp with slew rate SR=1v/µsec has a gain of 40db.if this amplifier
has to faithfully amplify sinusoidal signals from dc to 20 KHz without introducing any slew-rate
induced distortion, then the input signal level must not exceed
A. 795mV
B. 395mV
C. 795 mV
D. 39.5mV

In the differential voltage gain & the common mode voltage gain of a differential amplifier
are 48db &2db respectively, then its common mode rejection ratio is
A.23dB
B.25dB
C. 46dB
D. 50dB
Generally, the gain of a transistor amplifier falls at high frequencies due to the
A. Internal Capacitance of the device
B. Coupling capacitor at the input
C. Skin effect
D. Coupling capacitor at the output
An amplifier without feedback has a voltage gain of 50,input resistance os 1 KΩ & Output
resistance of 2.5KΩ.The input resistance of the current-shunt negative feedback amplifier using
the above amplifier with a feedbacik factor of 0.2 is
A. 1/11KΩ
B. 1/5KΩ
C. 5KΩ
D. 11KΩ
The action of JFET in its equivalent circuit can best be represented as a
A. Current controlled Current source
B. Current controlled voltage source
C. Voltage controlled voltage source
D. voltage controlled current source
Three identical amplifiers with each one having a voltage gain of 50,input resistance of 1KΩ
& output resistance of 250 ,are cascaded.The open circuit voltage gain of combined amplifier is
A. 49dB
B. 51dB
C. 98dB
D. 102dB
An ideal OP-AMP is an ideal
A. Current controlled Current source
B. Current controlled voltage source
C. Voltage controlled voltage source
D. voltage controlled current source
In a full-wave rectifier using two ideal diodes,Vdc & Vm are the dc & peak values of the
voltage respectively across a resistive load. If PIV is the peak inverse voltage of the diode, then
the appropriate relationships for this rectifier is.
A. Vdc = Vm/π, PIV=2Vm
B. Vdc = 2Vm/π, PIV=2vm
C. Vdc = 2Vm/π, PIV=Vm
D. Vdc = Vm/π, PIV=Vm
The cascade amplifier is a multistage configuration of
A. CC-CB .
B. CE-CB
C. CB-CC
D. CE-CC
The current gain of a BJT is
A. gm r0
B. gm / r0
C. gm rπ
D. gm /rπ
The most commonly used amplifier in sample & hold circuits is
A. A unity gain non-inverting amplifier
B. A unity gain inverting amplifier
C. An inverting amplifier with a gain of 10
D. An inverting amplifiers with a gain of 100
To prevent a DC return between source and load, it is necessary to use
resistor between source and load
B. inductor between source and load
C. capacitor between source and load
D. either A. or B.
Introducing a resistor in the emitter of a common amplifier stabilizes the dc operating point
against variations in
A. Only the temperature
B. only the β of the transistor
C. Both Temperature & β
D. None of the above
Voltage Series feedback also called series-shunt feedback) results in
A. Increase in both input & output impedances
B. Decreases in both input & output impedances
C. Increase in input impedance & decreases in output impedance
D. Decrease in input impedance & increase in output impedance
The encapsulation of transistor is necessary for
preventing radio interference
B. preventing photo-emission effects
C. avoiding loss of free electrons
D. mechanical ruggedness

Answer: D

In a transistor leakage current mainly depends on
doping of base
B. size of emitter
C. rating of transistor
D. temperature

Answer: D

In a CB amplifier the maximum efficiency could be
99%
B. 85%
C. 50%
D. 25%

Answer: D

When a transistor is connected in common emitter mode, it with have
negligible input resistance and high output resistance
B. high input resistance and low output resistance
C. medium input resistance and high output resistance
D. low input resistance as well as output resistance

Answer: C

In all base driver amplifiers
ac collector voltage is 180° out of phase with ac base voltage
B. ac emitter voltage is 180° out of phase with ac base voltage
C. ac collector voltage is in phase with ac base voltage
D. none of the above

Answer: A

The horizontal intercept of dc load line is the same as ideal
cut off point
B. saturation point
C. operating point
D. quasi saturation point

Answer: A

In deriving ac equivalent circuit for an amplifier circuit we short circuit
all resistors
B. all transistors
C. all inductors
D. all capacitors

Answer: D

Which of the following statements is false?
Push pull signals are equal and opposite in phase
B. Class AB operation cannot be used for a push pull audio power output phase
C. A push pull output transformer has a centre-tapped primary
D. All of the above

Answer: B

Which of the following amplifier circuit using junction transistor has the best gain?
Common base
B. Common emitter
C. Common collector
D. All have the same gain

Answer: B

In an op-amp differentiator
the amplitude of output is proportional to rate of change of input
B. the amplitude of output is proportional to input
C. output occurs when input is finite and constant
D. polarity of input and output is the same

Answer: A

Answers:- 1. C 2. B 3. A 4. A 5. A 6. D 7. D 8. B 9. A 10. B 11. D 12. C
13. B 14. C 15. B 16. C 17. A 18. D 19. C 20. D 21. A 22. B 23. A
24. A 25. B 26. B 27. C 28. C 29. A 30. A 31. D 32. C 33. B
34. B 35. B 36. C 37. B 38. C 39. C 40. C.

SEMICONDUCTOR THEORY

A semiconductor is formed by ……… bonds.
Covalent
B. Electrovalent
C. Co-ordinate
D. None of the above
ANS:- A
A semiconductor has ………… temperature coefficient of resistance.

Positive
Zero
Negative
None of the above
ANS:- C

The most commonly used semiconductor is ………..

Germanium
Silicon
Carbon
Sulphur
ANS:- B

SEMICONDUCTOR THEORY Questions and Answers pdf

A semiconductor has generally ……………… valence electrons.

2
3
6
4
ANS:- D

The resistivity of pure germanium under standard conditions is about ……….

6 x 104
O cm
60
O cm
3 x 106
O cm
6 x 10-4
O cm
ANS:- B

The resistivity of a pure silicon is about ……………

100 O cm
6000 O cm
3 x 105 O m
6 x 10-8 O cm
ANS:- B

When a pure semiconductor is heated, its resistance …………..

Goes up
Goes down
Remains the same
Can’t say
ANS:- B

The strength of a semiconductor crystal comes from ……..

Forces between nuclei
Forces between protons
Electron-pair bonds
None of the above
ANS:- C

When a pentavalent impurity is added to a pure semiconductor, it becomes ………

An insulator
An intrinsic semiconductor
p-type semiconductor
n-type semiconductor
ANS:- D

Addition of pentavalent impurity to a semiconductor creates many ……..

Free electrons
Holes
Valence electrons
Bound electrons
ANS:- A

A pentavalent impurity has ………. Valence electrons

3
5
4
6
ANS:- B

An n-type semiconductor is ………

Positively charged
Negatively charged
Electrically neutral
None of the above
ANS:- C

A trivalent impurity has ….. valence electrons

4
5
6
3
ANS:- D

Addition of trivalent impurity to a semiconductor creates many ……..

Holes
Free electrons
Valence electrons
Bound electrons
ANS:- A

A hole in a semiconductor is defined as …………….

A free electron
The incomplete part of an electron pair bond
A free proton
A free neutron
ANS:- B

The impurity level in an extrinsic semiconductor is about ….. of pure semiconductor.

10 atoms for 108 atoms
1 atom for 108 atoms
1 atom for 104 atoms
1 atom for 100 atoms
ANS:- B

As the doping to a pure semiconductor increases, the bulk resistance of the semiconductor ………..

Remains the same
Increases
Decreases
None of the above
ANS:- C

A hole and electron in close proximity would tend to ……….

Repel each other
Attract each other
Have no effect on each other
None of the above
ANS:- B

In a semiconductor, current conduction is due to ……..

Only holes
Only free electrons
Holes and free electrons
None of the above
ANS:- C

The random motion of holes and free electrons due to thermal agitation is called ……….

Diffusion
Pressure
Ionisation
None of the above
ANS:- A

A forward biased pn junction diode has a resistance of the order of

O
kO
MO
None of the above
ANS:- A

The battery connections required to forward bias a pn junction are ……

+ve terminal to p and –ve terminal to n
-ve terminal to p and +ve terminal to n
-ve terminal to p and –ve terminal to n
None of the above
ANS:- A

The barrier voltage at a pn junction for germanium is about ………

5 V
3 V
Zero
3 V
ANS:- D

In the depletion region of a pn junction, there is a shortage of ……..

Acceptor ions
Holes and electrons
Donor ions
None of the above
ANS:- B

A reverse bias pn junction has …………

Very narrow depletion layer
Almost no current
Very low resistance
Large current flow
ANS:- B

A pn junction acts as a ……….

Controlled switch
Bidirectional switch
Unidirectional switch
None of the above
ANS:- C

A reverse biased pn junction has resistance of the order of

O
kO
MO
None of the above
ANS:- C

The leakage current across a pn junction is due to …………..

Minority carriers
Majority carriers
Junction capacitance
None of the above
ANS:- A

When the temperature of an extrinsic semiconductor is increased, the pronounced effect is on……

Junction capacitance
Minority carriers
Majority carriers
None of the above
ANS:- B

With forward bias to a pn junction , the width of depletion layer ………

Decreases
Increases
Remains the same
None of the above
ANS:- A

The leakage current in a pn junction is of the order of

Aa
mA
kA
µA
ANS:- D

In an intrinsic semiconductor, the number of free electrons ………

Equals the number of holes
Is greater than the number of holes
Is less than the number of holes
None of the above
ANS:- A

At room temperature, an intrinsic semiconductor has ……….

Many holes only
A few free electrons and holes
Many free electrons only
No holes or free electrons
ANS:- B

At absolute temperature, an intrinsic semiconductor has ……….

A few free electrons
Many holes
Many free electrons
No holes or free electrons
ANS:- D

At room temperature, an intrinsic silicon crystal acts approximately as ……

A battery
A conductor
An insulator
A piece of copper wire
ANS:- C

SEMICONDUCTOR DIODE

A crystal diode has ………

one pn junction
two pn junctions
three pn junctions
none of the above
ANS: 1

A crystal diode has forward resistance of the order of ……………

kΩ
Ω
MΩ
none of the above
ANS: 2

If the arrow of crystal diode symbol is positive w.r.t. bar, then diode is ………….. biased.

forward
reverse
either forward or reverse
none of the above
ANS: 1

SEMICONDUCTOR DIODE Questions and Answers pdf

The reverse current in a diode is of the order of ……………….

kA
mA
μA
A
ANS: 3

The forward voltage drop across a silicon diode is about …………………

2.5 V
3 V
10 V
0.7 V
ANS: 4

A crystal diode is used as ……………

an amplifier
a rectifier
an oscillator
a voltage regulator
ANS: 2

The d.c. resistance of a crystal diode is ………….. its a.c. resistance

the same as
more than
less than
none of the above
ANS: 3

An ideal crystal diode is one which behaves as a perfect ……….. when forward biased.

conductor
insulator
resistance material
none of the above
ANS: 1

The ratio of reverse resistance and forward resistance of a germanium crystal diode is about ………….

1 : 1
100 : 1
1000 : 1
40,000 : 1
ANS: 4

The leakage current in a crystal diode is due to …………….

minority carriers
majority carriers
junction capacitance
none of the above
ANS: 1

If the temperature of a crystal diode increases, then leakage current ………..

remains the same
decreases
increases
becomes zero
ANS: 3

The PIV rating of a crystal diode is ………….. that of equivalent vacuum diode

the same as
lower than
more than
none of the above
ANS: 2

If the doping level of a crystal diode is increased, the breakdown voltage………….

remains the same
is increased
is decreased
none of the above
ANS: 3

The knee voltage of a crystal diode is approximately equal to ………….

applied voltage
breakdown voltage
forward voltage
barrier potential
ANS: 4

When the graph between current through and voltage across a device is a straight line, the device is referred to as ……………….

linear
active
nonlinear
passive
ANS: 1

When the crystal current diode current is large, the bias is …………

forward
inverse
poor
reverse
ANS: 1

A crystal diode is a …………… device

non-linear
bilateral
linear
none of the above
ANS: 1

A crystal diode utilises …………….. characteristic for rectification

reverse
forward
forward or reverse
none of the above
ANS: 2

When a crystal diode is used as a rectifier, the most important consideration is ………..

forward characteristic
doping level
reverse characteristic
PIC rating
ANS: 4

If the doping level in a crystal diode is increased, the width of depletion layer………..

remains the same
is decreased
in increased
none of the above
ANS: 3

A zener diode has ………..

one pn junction
two pn junctions
three pn junctions
none of the above
ANS: 1

A zener diode is used as …………….

an amplifier
a voltage regulator
a rectifier
a multivibrator
ANS: 2

The doping level in a zener diode is …………… that of a crystal diode

the same as
less than
more than
none of the above
ANS: 3

A zener diode is always ………… connected.

reverse
forward
either reverse or forward
none of the above
ANS: 1

A zener diode utilizes ……….. characteristics for its operation.

forward
reverse
both forward and reverse
none of the above
ANS: 2

In the breakdown region, a zener didoe behaves like a …………… source.

constant voltage
constant current
constant resistance
none of the above
ANS: 1

A zener diode is destroyed if it…………..

is forward biased
is reverse biased
carrier more than rated current
none of the above
ANS: 3

A series resistance is connected in the zener circuit to………..

properly reverse bias the zener
protect the zener
properly forward bias the zener
none of the above
ANS: 2

A zener diode is …………………. device

a non-linear
a linear
an amplifying
none of the above
ANS: 1

A zener diode has ………….. breakdown voltage

undefined
sharp
zero
none of the above
ANS: 2

……………. rectifier has the lowest forward resistance

solid state
vacuum tube
gas tube
none of the above
ANS: 1

Mains a.c. power is converrted into d.c. power for ……………..

lighting purposes
heaters
using in electronic equipment
none of the above
ANS: 3

The disadvantage of a half-wave rectifier is that the……………….

components are expensive
diodes must have a higher power rating
output is difficult to filter
none of the above
ANS: 3

If the a.c. input to a half-wave rectifier is an r.m.s value of 400/√2 volts, then diode PIV rating is ………………….

400/√2 V
400 V
400 x √2 V
none of the above
ANS: 2

The ripple factor of a half-wave rectifier is …………………

2
1.21
2.5
0.48
ANS: 4

There is a need of transformer for ………………..

half-wave rectifier
centre-tap full-wave rectifier
bridge full-wave rectifier
none of the above
ANS: 2

The PIV rating of each diode in a bridge rectifier is ……………… that of the equivalent centre-tap rectifier

one-half
the same as
twice
four times
ANS: 1

For the same secondary voltage, the output voltage from a centre-tap rectifier is ………… than that of bridge rectifier

twice
thrice
four time
one-half
ANS: 4

If the PIV rating of a diode is exceeded, ………………

the diode conducts poorly
the diode is destroyed
the diode behaves like a zener diode
none of the above
ANS: 2

A 10 V power supply would use …………………. as filter capacitor.

paper capacitor
mica capacitor
electrolytic capacitor
air capacitor
ANS: 3

A 1,000 V power supply would use ……….. as a filter capacitor

paper capacitor
air capacitor
mica capacitor
electrolytic capacitor
ANS: 1

The ……………….. filter circuit results in the best voltage regulation

choke input
capacitor input
resistance input
none of the above
ANS: 1

A half-wave rectifier has an input voltage of 240 V r.m.s. If the step-down transformer has a turns ratio of 8:1, what is the peak load voltage? Ignore diode drop.

27.5 V
86.5 V
30 V
42.5 V
ANS: 4

The maximum efficiency of a half-wave rectifier is ………………..

40.6 %
81.2 %
50 %
25 %
ANS: 1

The most widely used rectifier is ……………….

half-wave rectifier
centre-tap full-wave rectifier
bridge full-wave rectifier
none of the above
ANS: 3

TRANSISTORS

A transistor has …………………
one pn junction
2. two pn junctions
3. three pn junctions
4. four pn junctions
ANS : 2
The number of depletion layers in a transistor is …………

four
three
one
two
ANS : 4

The base of a transistor is ………….. doped

heavily
moderately
lightly
none of the above
ANS : 3

TRANSISTORS Questions and Answers pdf

The element that has the biggest size in a transistor is ………………..

collector
base
emitter
collector-base-junction
ANS : 1

In a pnp transistor, the current carriers are ………….

acceptor ions
donor ions
free electrons
holes
ANS : 4

The collector of a transistor is …………. doped

heavily
moderately
lightly
none of the above
ANS : 2

A transistor is a …………… operated device

current
voltage
both voltage and current
none of the above
ANS : 1

In a npn transistor, ……………. are the minority carriers

free electrons
holes
donor ions
acceptor ions
ANS : 2

The emitter of a transistor is ………………… doped

lightly
heavily
moderately
none of the above
ANS : 2

In a transistor, the base current is about ………….. of emitter current

25%
20%
35 %
5%
ANS : 4

At the base-emitter junctions of a transistor, one finds ……………

a reverse bias
a wide depletion layer
low resistance
none of the above
ANS : 3

The input impedance of a transistor is ………….

high
low
very high
almost zero
ANS : 2

Most of the majority carriers from the emitter ………………..

recombine in the base
recombine in the emitter
pass through the base region to the collector
none of the above
ANS :3

The current IB is …………

electron current
hole current
donor ion current
acceptor ion current
ANS : 1

In a transistor ………………..

IC = IE + IB

IB = IC + IE

IE = IC – IB

IE = IC + IB

ANS : 4

The value of a of a transistor is ……….

more than 1
less than 1
1
none of the above
ANS : 2

IC = aIE + ………….

IB
ICEO
ICBO
ßIB
ANS : 3

The output impedance of a transistor is ……………..

high
zero
low
very low
ANS : 1

In a tansistor, IC = 100 mA and IE = 100.2 mA. The value of ß is …………

100
50
about 1
200
ANS : 4

In a transistor if ß = 100 and collector current is 10 mA, then IE is …………

100 mA
100.1 mA
110 mA
none of the above
ANS : 2

The relation between ß and a is …………..

ß = 1 / (1 – a )
ß = (1 – a ) / a
ß = a / (1 – a )
ß = a / (1 + a )
ANS : 3

The value of ß for a transistor is generally ………………..

1
less than 1
between 20 and 500
above 500
ANS : 3

The most commonly used transistor arrangement is …………… arrangement

common emitter
common base
common collector
none of the above
ANS : 1

The input impedance of a transistor connected in …………….. arrangement is the highest

common emitter
common collector
common base
none of the above
ANS : 2

The output impedance of a transistor connected in ……………. arrangement is the highest

common emitter
common collector
common base
none of the above
ANS : 3

The phase difference between the input and output voltages in a common base arrangement is …………….

180o
90o
270o
0o
ANS : 4

The power gain in a transistor connected in ……………. arrangement is the highest

common emitter
common base
common collector
none of the above
ANS : 1

The phase difference between the input and output voltages of a transistor connected in common emitter arrangement is ………………

0o
180o
90o
270o
ANS : 2

The voltage gain in a transistor connected in ………………. arrangement is the highest

common base
common collector
common emitter
none of the above
ANS : 3

As the temperature of a transistor goes up, the base-emitter resistance ……………

decreases
increases
remains the same
none of the above
ANS : 1

The voltage gain of a transistor connected in common collector arrangement is ………..

equal to 1
more than 10
more than 100
less than 1
ANS : 4

The phase difference between the input and output voltages of a transistor connected in common collector arrangement is ………………

180o
0o
90o
270o
ANS : 2

IC = ß IB + ………..

ICBO
IC
ICEO
aIE
ANS : 3

IC = [a / (1 – a )] IB + ………….

ICEO
ICBO
IC
(1 – a ) IB
ANS : 1

IC = [a / (1 – a )] IB + […….. / (1 – a )]

ICBO
ICEO
IC
IE
ANS : 1

BC 147 transistor indicates that it is made of …………..

germanium
silicon
carbon
none of the above
ANS : 2

ICEO = (………) ICBO

ß
1 + a
1 + ß
none of the above
ANS : 3

A transistor is connected in CB mode. If it is not connected in CE mode with same bias voltages, the values of IE, IB and IC will …………..

remain the same
increase
decrease
none of the above
ANS : 1

If the value of a is 0.9, then value of ß is ………..

9
0.9
900
90
ANS : 4

In a transistor, signal is transferred from a …………… circuit

high resistance to low resistance
low resistance to high resistance
high resistance to high resistance
low resistance to low resistance
ANS : 2

The arrow in the symbol of a transistor indicates the direction of ………….

electron current in the emitter
electron current in the collector
hole current in the emitter
donor ion current
ANS : 3

The leakage current in CE arrangement is ……………. that in CB arrangement

more than
less than
the same as
none of the above
ANS : 1

A heat sink is generally used with a transistor to …………

increase the forward current
decrease the forward current
compensate for excessive doping
prevent excessive temperature rise
ANS : 4

The most commonly used semiconductor in the manufacture of a transistor is ………….

germanium
silicon
carbon
none of the above
ANS : 2

The collector-base junction in a transistor has ……………..

forward bias at all times
reverse bias at all times
low resistance
none of the above
ANS : 2

TRANSISTOR BIASING

Transistor biasing represents ……………. conditions
c.
c.
both a.c. and d.c.
none of the above

Ans : 2

Transistor biasing is done to keep ………… in the circuit

Proper direct current
Proper alternating current
The base current small
Collector current small
Ans : 1

Operating point represents …………..

Values of IC and VCE when signal is applied
The magnitude of signal
Zero signal values of IC and VCE
None of the above
Ans : 3

If biasing is not done in an amplifier circuit, it results in ……………

Decrease in the base current
Unfaithful amplification
Excessive collector bias
None of the above
Ans : 2

Transistor biasing is generally provided by a …………….

Biasing circuit
Bias battery
Diode
None of the above
Ans : 1

For faithful amplification by a transistor circuit, the value of VBE should ………. for a silicon transistor

Be zero
Be 0.01 V
Not fall below 0.7 V
Be between 0 V and 0.1 V
Ans : 3

For proper operation of the transistor, its collector should have …………

Proper forward bias
Proper reverse bias
Very small size
None of the above
Ans : 2

For faithful amplification by a transistor circuit, the value of VCE should ……….. for silicon transistor

Not fall below 1 V
Be zero
Be 0.2 V
None of the above
Ans : 1

The circuit that provides the best stabilization of operating point is …………

Base resistor bias
Collector feedback bias
Potential divider bias
None of the above
Ans : 3

The point of intersection of d.c. and a.c. load lines represents …………..

Operating point
Current gain
Voltage gain
None of the above
Ans : 1

An ideal value of stability factor is …………..

100
200
More than 200
1
Ans : 4

The zero signal IC is generally ……………… mA in the initial stages of a transistor amplifier

4
1
3
More than 10
Ans : 2

If the maximum collector current due to signal alone is 3 mA, then zero signal collector current should be at least equal to ………..

6 mA
mA
3 mA
1 mA
Ans : 3

The disadvantage of base resistor method of transistor biasing is that it …………

Is complicated
Is sensitive to changes in ß
Provides high stability
None of the above
Ans : 2

The biasing circuit has a stability factor of 50. If due to temperature change, ICBO changes by 1 µA, then IC will change by …………

100 µA
25 µA
20 µA
50 µA
Ans : 4

For good stabilsation in voltage divider bias, the current I1 flowing through R1 and R2 should be equal to or greater than

10 IB
3 IB
2 IB
4 IB
Ans : 1

The leakage current in a silicon transistor is about ………… the leakage current in a germanium transistor

One hundredth
One tenth
One thousandth
One millionth
Ans : 3

The operating point is also called the ………….

Cut off point
Quiescent point
Saturation point
None of the above
Ans : 2

For proper amplification by a transistor circuit, the operating point should be located at the ………….. of the d.c. load line

The end point
Middle
The maximum current point
None of the above
Ans : 2

The operating point ………………… on the a.c. load line

Also line
Does not lie
May or may not lie
Data insufficient
Ans : 1

The disadvantage of voltage divider bias is that it has ………….

High stability factor
Low base current
Many resistors
None of the above
Ans : 3

Thermal runaway occurs when ……….

Collector is reverse biased
Transistor is not biased
Emitter is forward biased
Junction capacitance is high
Ans : 2

The purpose of resistance in the emitter circuit of a transistor amplifier is to ………….

Limit the maximum emitter current
Provide base-emitter bias
Limit the change in emitter current
None of the above
Ans : 3

In a transistor amplifier circuit VCE = VCB + ……………..

VBE
2VBE
5 VBE
None of the above
Ans : 1

The base resistor method is generally used in ………

Amplifier circuits
Switching circuits
Rectifier circuits
None of the above
Ans : 2

For germanium transistor amplifier, VCE should ………….. for faithful amplification

Be zero
Be 0.2 V
Not fall below 0.7 V
None of the above
Ans : 3

In a base resistor method, if the value of ß changes by 50, then collector current will change by a factor ………

25
50
100
200
Ans : 2

The stability factor of a collector feedback bias circuit is ……….. that of base resistor bias.

The same as
More than
Less than
None of the above
Ans : 3

In the design of a biasing circuit, the value of collector load RC is determined by …………

VCE consideration
VBE consideration
IB consideration
None of the above
Ans : 1

If the value of collector current IC increases, then the value of VCE …………

Remains the same
Decreases
Increases
None of the above
Ans : 2

If the temperature increases, the value of VCE …………

Remains the same
Is increased
Is decreased
None of the above
Ans : 3

The stabilisation of operating point in potential divider method is provided by ……….

RE consideration
RC consideration
VCC consideration
None of the above
Answer: 1

The value of VBE …………….

Depends upon IC to moderate extent
Is almost independent of IC
Is strongly dependant on IC
None of the above
Ans : 2

When the temperature changes, the operating point is shifted due to …….

Change in ICBO
Change in VCC
Change in the values of circuit resistance
None of the above
Ans : 1

The value of stability factor for a base resistor bias is …………

RB (ß+1)
(ß+1)RC
(ß+1)
1-ß
Ans : 3

In a particular biasing circuit, the value of RE is about ………

10 kO
1 MO
100 kO
800 O
Ans : 4

A silicon transistor is biased with base resistor method. If ß=100, VBE =0.7 V, zero signal collector current IC = 1 mA and VCC = 6V , what is the value of the base resistor RB?

105 kO
530 kO
315 kO
None of the above
Ans : 2

In voltage divider bias, VCC = 25 V; R1 = 10 kO; R2 = 2.2 V ; RC = 3.6 V and RE =1 kO. What is the emitter voltage?

7 V
3 V
V
8 V
Ans : 4

In the above question (Q38.) , what is the collector voltage?

3 V
8 V
6 V
7 V
Ans : 1

In voltage divider bias, operating point is 3 V, 2 mA. If VCC = 9 V, RC = 2.2 kO, what is the value of RE ?

2000 O
1400 O
800 O
1600 O
Ans : 3

SINGLE STAGE TRANSISTOR AMPLIFIERS

A single stage transistor amplifier contains ……………. and associated circuitry

Two transistors
One transistor
Three transistor
None of the above
Ans : 2

The phase difference between the output and input voltages of a CE amplifier is ………………..

180o
0o
90o
270o
Ans : 1

It is generally desired that a transistor should have …………….. input impedance

Low
Very low
High
Very high
Ans : 3

When an a.c. signal is applied to an amplifier, ,the operating point moves along …………….
load line
c. load line
both d.c. and a.c. load lines
none of the above
Ans : 2
If the collector supply is 10V, then collector cut off voltage under d.c. conditions is ………….

20 V
5 V
2 V
10 V
Ans : 4

In the zero signal conditions, a transistor sees ……………….. load

c.
c.
both d.c. and a.c.
none of the above
Ans : 1

The input capacitor in an amplifier is the ……………….. capacitor

Coupling
Bypass
Leakage
None of the above
Ans : 1

The point of intersection of d.c. and a.c. load lines is called ……………..

Saturation point
Cut off point
Operating point
None of the above
Ans : 3

The slope of a.c. load line is ……………… that of d.c. load line

The same as
More than
Less than
None of the above
Ans : 2

If a transistor amplifier draws 2mA when input voltage is 10 V, then its input impedance is ………..

20 kΩ
2 kΩ
10 kΩ
5 kΩ
Ans : 4

When a transistor amplifier is operating, the current in any branch is ……………

Sum of a.c. and d.c.
c. only
c. only
difference of a.c. and d.c.
Ans : 1

The purpose of capacitors in a transistor amplifier is to ………………

Protect the transistor
Cool the transistor
Couple or bypass a.c. component
Provide biasing
Ans : 3

In the d.c. equivalent circuit of a transistor amplifier, the capacitors are considered ……………..

Short
Open
Partially short
None of the above
Answer : 2

In a CE amplifier, voltage gain = ……………. x RAC/Rin

α
(1 + α)
(1+ β)
β
Ans : 4

Q15. In practice, the voltage gain of an amplifier is expressed ……………..

As volts
As a number
In db
None of the above
Ans : 3

If the power and current gains of a transistor amplifier are 16500 and 100 respectively, then voltage gain is ………

165
165 x 104
100
None of the above
Ans : 1

If RC and RL represent the collector resistance and load resistance respectively in a single stage transistor amplifier, then a.c. load is ……..

RL + RC
RC || RL
RL – RC
RC
Ans : 2

In a CE amplifier, the phase difference between voltage across collector load RC and signal voltage is ………..

180o
270o
90o
0o
Ans : 4

In the a.c. equivalent circuit of a transistor amplifier, the capacitors are considered ………….

Short
Open
Partially open
None of the above
Ans : 1

In a single stage transistor amplifier, RC and RL represent collector resistance and load resistance respectively. The transistor sees a d.c. load of ………..

RC + RL
RC || RL
RL
RC
Ans : 4

The purpose of d.c. conditions in a transistor is to …………..

Reverse bias the emitter
Forward bias the collector
Set up operating point
None of the above
Ans : 3

An amplifier has a power gain of 100. Its db gain is ……………

10 db
20 db
40 db
None of the above
Ans : 2

In order to get more voltage gain from a transistor amplifier, the transistor used should have …………..

Thin base
Thin collector
Wide emitter
None of the above
Ans : 1

The purpose of a coupling capacitor in a transistor amplifier is to ……….

Increase the output impedance of transistor
Protect the transistor
Pass a.c. and block d.c.
Provide biasing
Ans : 3

The purpose of emitter capacitor (i.e. capacitor across RE) is to ……….

Avoid voltage gain drop
Forward bias the emitter
Reduce noise in the amplifier
None of the above
Ans : 1

The ratio of output impedance of a CE amplifier is ……………

About 1
Low
High
Moderate
Ans : 4

If a transistor amplifier feeds a load of low resistance (e.g. speaker), then voltage gain will be ………….

High
Very high
Moderate
Low
Ans : 4

If the input capacitor of a transistor amplifier is short-circuited, then………

Transistor will be destroyed
Biasing conditions will change
Signal will not reach the base
None of the above
Ans : 2

The radio wave picked up by the receiving antenna is amplified about …….. times to have reasonable sound output

1000
A million
100
10000
Ans : 2

A CE amplifier is also called ………….. circuit

Grounded emitter
Grounded base
Grounded collector
None of the above
Ans : 1

The d.c. load of a transistor amplifier is generally ………….. that of a a.c. load

The same as
Less than
More than
None of the above
Ans : 3

The value of collector load RC in a transistor amplifier is ………… the output impedance of the transistor.

The same as
Less than
More than
None of the above
Ans : 2

A single stage transistor amplifier with collector load RC and emitter resistance RE has a d.c. load of ……….

RC
RC || RE
RC – RE
RC + RE
Ans : 4

In transistor amplifiers, we generally use ………….. capacitors.

Electrolytic
Mica
Paper
Air
Ans : 1

A single stage transistor amplifier with no load sees an a.c. load of ……..

RC + RE
RC
RC || RE
RC/RE
Ans : 2

The output power of a transistor amplifier is more than the input power because the additional power is supplied by …………

Transistor
Biasing circuit
Collector supply VCC
None of the above
Ans : 3

A transistor converts ……………
power into a.c. power
c. power into d.c. power
high resistance into low resistance
none of the above
Ans : 1
A transistor amplifier has high output impedance because ………..

Emitter is heavily doped
Collector has reverse bias
Collector is wider than emitter or base
None of the above
Ans : 2

For highest power gain, one would use …………….. configuration

CC
CB
CE
none of the above
Ans : 3

CC configuration is used for impedance matching because its ……………..

Input impedance is very high
Input impedance is low
Output impedance is very low
None of the above
Ans : 1

MULTISTAGE TRANSISTOR AMPLIFIERS

A radio receiver has …………… of amplification

One stage
Two stages
Three stages
More than one stages
Ans : 4

RC coupling is used for ………………. amplification

Voltage
Current
Power
None of the above
Ans : 1

In an RC coupled amplifier, the voltage gain over mid-frequency range …………….

Changes abruptly with frequency
Is constant
Changes uniformly with frequency
None of the above
Ans : 2

In obtaining the frequency response curve of an amplifier, the …………

Amplifier level output is kept constant
Amplifier frequency is held constant
Generator frequency is held constant
Generator output level is held constant
Ans : 4

An advantage of RC coupling scheme is the ………….

Good impedance matching
Economy
High efficiency
None of the above
Ans : 2

The best frequency response is of ………. coupling

RC
Transformer
Direct
None of the above
Ans : 3

Transformer coupling is used for ………….. amplification

Power
Voltage
Current
None of the above
Ans : 1

In an RC coupling scheme, the coupling capacitor CC must be large enough ………..

To pass d.c. between the stages
Not to attenuate the low frequencies
To dissipate high power
None of the above
Ans : 2

In RC coupling, the value of coupling capacitor is about ……….

100 pF
0.1 µF
0.01 µF
10 µF
Ans : 4

The noise factor of an ideal amplifier expressed in db is …………..

0
1
1
10
Ans : 1

When a multistage amplifier is to amplify d.c. signal, then one must use …….. coupling

RC
Transformer
Direct
None of the above
Ans : 3

………….. coupling provides the maximum voltage gain

RC
Transformer
Direct
Impedance
Ans : 2

In practice, voltage gain is expressed ……………

In db
In volts
As a number
None of the above
Ans : 1

Transformer coupling provides high efficiency because …………

Collector voltage is stepped up
c. resistance is low
collector voltage is stepped down
none of the above
Ans : 2

Transformer coupling is generally employed when load resistance is ………

Large
Very large
Small
None of the above
Ans : 3

If a three-stage amplifier has individual stage gains of 10 db, 5 db and 12 db, then total gain in db is ……….

600 db
24 db
14 db
27 db
Ans : 4

The final stage of a multistage amplifier uses ………………

RC coupling
Transformer coupling
Direct coupling
Impedance coupling
Ans : 2

The ear is not sensitive to ………….

Frequency distortion
Amplitude distortion
Frequency as well as amplitude distortion
None of the above
Ans : 1

RC coupling is not used to amplify extremely low frequencies because ………

There is considerable power loss
There is hum in the output
Electrical size of coupling capacitor becomes very large
None of the above
Ans : 3

In transistor amplifiers, we use ……………. transformer for impedance matching

Step up
Step down
Same turn ratio
None of the above
Ans : 2

The lower and upper cut off frequencies are also called ………………… frequencies

Sideband
Resonant
Half-resonant
Half-power
Ans : 4

A gain of 1,000,000 times in power is expressed by …………….

30 db
60 db
120 db
600 db
Ans : 2

A gain of 1000 times in voltage is expressed by …………..

60 db
30 db
120 db
600 db
Ans : 1

1 db corresponds to ………….. change in power level

50%
35%
26%
22%
Ans : 3

1 db corresponds to …………. change in voltage or current level

40%
80%
20%
25%
Ans : 1

The frequency response of transformer coupling is ………….

Good
Very good
Excellent
Poor
Ans : 4

In the initial stages of a multistage amplifier, we use ………..

RC coupling
Transformer coupling
Direct coupling
None of the above
Ans : 1

The total gain of a multistage amplifier is less than the product of the gains of individual stages due to …………

Power loss in the coupling device
Loading effect of the next stage
The use of many transistors
The use of many capacitors
Ans : 2

The gain of an amplifier is expressed in db because ………..

It is a simple unit
Calculations become easy
Human ear response is logarithmic
None of the above
Ans : 3

If the power level of an amplifier reduces to half, the db gain will fall by …….

5 db
2 db
10 db
3 db
Ans : 4

A current amplification of 2000 is a gain of …………….

3 db
66 db
20 db
200 db
Ans : 2

An amplifier receives 0.1 W of input signal and delivers 15 W of signal power. What is the power gain in db?

8 db
6 db
5 db
4 db
Ans : 1

The power output of an audio system is 18 W. For a person to notice an increase in the output (loudness or sound intensity) of the system, what must the output power be increased to ?

2 W
6 W
68 W
None of the above
Ans : 3

The output of a microphone is rated at -52 db. The reference level is 1V under specified conditions. What is the output voltage of this microphone under the same sound conditions?

5 mV
2 mV
8 mV
5 mV
Ans : 4

RC coupling is generally confined to low power applications because of ………

Large value of coupling capacitor
Low efficiency
Large number of components
None of the above
Ans : 2

The number of stages that can be directly coupled is limited because ……..

Changes in temperature cause thermal instability
Circuit becomes heavy and costly
It becomes difficult to bias the circuit
None of the above
Ans : 1

The purpose of RC or transformer coupling is to …………

Block a.c.
Separate bias of one stage from another
Increase thermal stability
None of the above
Ans : 2

The upper or lower cut off frequency is also called ………….. frequency

Resonant
Sideband
3 db
None of the above
Ans : 3

The bandwidth of a single stage amplifier is …………. that of a multistage amplifier

More than
The same as
Less than
Data insufficient
Ans : 1

The value of emitter capacitor CE in a multistage amplifier is about ……..

1 µF
100 pF
0.01 µF
50 µF
Ans : 4

TRANSISTOR AUDIO POWER AMPLIFIERS

The output stage of a multistage amplifier is also called ……………

Mixer stage
Power stage
Detector stage
F stage
Ans : 2

………………. coupling is generally employed in power amplifiers

Transformer
RC
direct
Impedance
Ans : 1

A class A power amplifier uses …………

Two transistors
Three transistors
One transistor
None of the above
Ans : 3

The maximum efficiency of resistance loaded class A power amplifier is ……..

5%
50%
30%
25%
Ans : 4

The maximum efficiency of transformer coupled class A power amplifier is ………………

30%
50%
80%
45%
Ans : 2

Class……. power amplifier has the highest collector efficiency

C
A
B
AB
Ans : 1

Power amplifiers handle …………. signals compare to voltage amplifiers

Small
Very small
Large
None of the above
Ans : 3

In class A operation, the operating point is generally located ………. of the d.c. load line.

At cut off point
At the middle
At saturation point
None of the above
Ans : 2

Class C amplifiers are used as …………….

AF amplifiers
Detectors
F. amplifiers
None of the above
Ans : 3

A power amplifier has comparatively …………….. ß

Small
Large
Very large
None of the above
Ans : 1

The maximum collector efficiency of class B operation is ……………..

50%
90%
5%
5%
Ans : 4

A 2-transistor class B power amplifier is commonly called ……….. amplifier

Dual
Push-pull
Symmetrical
Differential
Ans : 2

If a transistor is operated in such a way that output current flows for 60o of the input signal, then it is …………… operation

Class A
Class B
Class C
None of the above
Ans : 3

If the zero signal dissipation of a transistor is 1W, then power rating of the transistor should be at least ……………….

5 W
33 W
75 W
1 W
Ans : 4

When a transistor is cut off……………..

Maximum voltage appears across transistor
Maximum current flows
Maximum voltage appears across load
None of the above
Ans : 1

A class A power amplifier is sometimes called ………….. amplifier

Symmetrical
Single-ended
Reciprocating
Differential
Ans : 2

Class ………….. operation gives the maximum distortion

A
B
C
AB
Ans : 3

The output stage of a multistage amplifier usually employs ………..

Push-pull amplifier
Preamplifier
Class A power amplifier
None of the above
Ans : 1

The size of a power transistor is made considerably large to …………

Provide easy handling
Dissipate heat
Facilitate connections
None of the above
Ans : 2

Low efficiency of a power amplifier results in ……………….

Low forward bias
Less battery consumption
More battery consumption
None of the above
Ans : 3

The driver stage usually employs………….

Class A power amplifier
Push-pull amplifier
Class C amplifier
None of the above
Ans : 1

If the power rating of a transistor is 1W and collector current is 100mA, then maximum allowable collector voltage is ………..

1V
100V
20V
10V
Ans : 4

When no signal is applied, the approximate collector efficiency of class A power amplifier is …….

10%
0%
25%
50%
Ans : 2

What will be the collector efficiency of a power amplifier having zero signal power dissipation of 5 watts and a.c. power output of 2 watts?

20%
80%
40%
50%
Ans : 3

The output signal voltage and current of a power amplifier are 5V and 200 mA; the values being r.m.s. What is the power output?

1 W
2 W
4 W
None of the above
Ans : 1

The maximum a.c. power output from a class A power amplifier is 10 W. What should be the minimum power rating of the transistor used ?

10 W
15 W
5 W
20 W
Ans : 4

For the same a.c. power output as above, what should be the minimum power rating of transistor for class B operation?

10 W
4 W
8 W
None of the above
Ans : 2

The push-pull circuit must use …………… operation

Class A
Class C
Class B
Class AB
Ans : 3

The class B push-pull circuit can deliver 100 W of a.c. output power. What should be the minimum power rating of each transistor?

20 W
40 W
10 W
80 W
Ans : 1

What turn ratio (Np/Ns) of transformer is required to match 4 O speaker to a transistor having an output impedance of 8000 O?

2
7
3
None of the above
Ans : 2

A transformer coupled class A power amplifier has a load of 100 O on the secondary. If the turn ratio is 10:1, what is the value of load appearing on the primary?

5 kO
20 kO
100 kO
10 kO
Ans : 4

Power amplifiers generally use transformer coupling because transformer permits……..

Cooling of the circuit
Impedance matching
Distortionless output
Good frequency response
Ans : 2

Transformer coupling can be used in …………… amplifiers

Either power or voltage
Only power
Only voltage
None of the above
Ans : 1

The output transformer used in a power amplifier is a ……………. transformer

1:1 ratio
Step-up
Step-down
None of the above
Ans : 3

The most important consideration in power amplifier is ………..

Biasing the circuit
Collector efficiency
To keep the transformer cool
None of the above
Ans : 2

An AF amplifier is shielded to …………

Keep the amplifier cool
Protect from rusting
Prevent induction due to stray magnetic fields
None of the above
Ans : 3

The pulsating d.c. applied to power amplifier causes ……………..

Burning of transistor
Hum in the circuit
Excessive forward voltage
None of the above
Ans : 2

The disadvantage of impedance matching is that it ………………….

Gives distorted output
Gives low power output
Requires a transformer
None of the above
Ans : 1

If the gain versus frequency curve of a transistor amplifier is not flat, then there is distortion.

Amplitude
Intermodulation
Frequency
None of the above
Ans : 3

The most costly coupling is ……………… coupling

RC
Direct
Impedance
Transformer
Ans : 4

OP AMP

A differential amplifier ……………..
is a part of an Op-amp
has one input and one output
has two outputs
answers (1) and (2)
Ans : 4
When a differential amplifier is operated single-ended, …………
the output is grounded
one input is grounded and signal is applied to the other
both inputs are connected together
the output is not inverted

Ans : 2

In differential-mode, …………….
opposite polarity signals are applied to the inputs
the gain is one
the outputs are of different amplitudes
only one supply voltage is used

Ans : 1

In the common mode, ……………

both inputs are grounded
the outputs are connected together
an identical signal appears on both the inputs
the output signal are in-phase
Ans : 3

The common-mode gain is ………..

very high
very low
always unity
unpredictable
Ans : 2

The differential gain is ………

very high
very low
dependent on input voltage
about 100
Ans : 1

If ADM = 3500 and ACM = 0.35, the CMRR is ……….

1225
10,000
80 dB
answers (1) and (3)
Ans : 4

With zero volts on both inputs, an OP-amp ideally should have an output ………..

equal to the positive supply voltage
equal to the negative supply voltage
equal to zero
equal to CMRR
Ans : 3

Of the values listed, the most realistic value for open-loop voltage gain of an OP-amp is ……

1
2000
80 dB
100,000
Ans : 4

A certain OP-amp has bias currents of 50 µA. The input offset current is ……..

700 nA
99.3 µA
49.7 µA
none of these
Ans : 1

The output of a particular Op-amp increases 8V in 12µs. The slew rate is …….

90 V/µs
0.67 V/µs
1.5 V/µs
none of these
Ans : 2

For an Op-amp with negative feedback, the output is …….

equal to the input
increased
fed back to the inverting input
fed back to the noninverting input
Ans : 3

The use of negative feedback ………

reduces the voltage gain of an Op-amp
makes the Op-amp oscillate
makes linear operation possible
answers (1) and (2)
Ans : 4

Negative feedback ………..

increases the input and output impedances
increases the input impedance and bandwidth
decreases the output impedance and bandwidth
does not affect impedance or bandwidth
Ans : 2

A certain noninverting amplifier has Ri of 1 kO and Rf of 100 kO. The closed-loop voltage gain is ………

100,000
1000
101
100
Ans : 3

If the feedback resistor in Q15 (above question) is open, the voltage gain …….

increases
decreases
is not affected
depends on Ri
Ans : 1

A certain inverting amplifier has a closed-loop voltage gain of 25. The Op-amp has an open-loop voltage gain of 100,000. If an Op-amp with an open-loop voltage gain of 200,000 is substituted in the arrangement, the closed-loop gain ……..

doubles
drops to 12.5
remains at 25
increases slightly
Ans : 3

A voltage follower ……….

has a voltage gain of 1
is noninverting
has no feedback resistor
has all of these
Ans : 4

The Op-amp can amplify

a.c. signals only
d.c. signals only
both a.c. and d.c. signals
neither d.c. nor a.c. signals
Ans : 3

The input offset current equals the ……….

difference between two base currents
average of two base currents
collector current divided by current gain
none of these
Ans : 1

The tail current of a differential amplifier is …….

half of either collector current
equal to either collector current
two times either collector current
equal to the difference in base currents
Ans : 3

The node voltage at the top of the til resistor is closes to ……….

collector supply voltage
zero
emitter supply voltage
tail current times base resistance
Ans : 2

The tail current in a differential amplifier equals …….

difference between two emitter currents
sum of two emitter currents
collector current divided by current gain
collector voltage divided by collector resistance
Ans : 2

The differential voltage gain of a differential amplifier is equal to RC divided by …….

r’e
r’e/2
2r’e
RE
Ans : 3

The input impedance of a differential amplifier equals r’e times ……

ß
RE
RC
2ß
Ans : 4

A common-mode signal is applied to ……….

the noninverting input
the inverting input
both iputs
top of the tail resistor
Ans : 3

The common-mode voltage gain is ………

smaller than differentail voltage gain
equal to differential voltage gain
greater than differential voltage gain
none of the above
Ans : 1

The input stage of an Op-amp is usually a ……….

differential amplifier
class B push-pull amplifier
CE amplifier
swamped amplifier
Ans : 1

The common-mode voltage gain of a differential amplifier is equal to RC divided by ……..

r’e
2r’e
r’e/2
2RE
Ans : 4

Current cannot flow to ground through …….

a mechanical ground
an a.c. ground
a virtual ground
an ordinary ground
Ans : 3

HYBRID PARAMETERS

Hybrid means ………………
Mixed
Single
Unique
None of the above
Ans : 1
There are …………… h parameters of a transistor
Two
Four
Three
None of the above
Answer: 2
The h parameter approach gives correct results for …………
Large signals only
Small signals only
Both small and large signals
None of the above
Answer: 2
A transistor behaves as a linear device for ………….

Small signals only
Large signals only
Both small and large signals
None of the above
Ans : 1

The parameter hie stands for input impedance in ………..

CB arrangement with output shorted
CC arrangement with output shorted
CE arrangement with output shorted
None of the above
Ans : 3

The dimensions of hie parameter are ………..

Mho
Ohm
Farad
None of the above
Ans : 2

The hfe parameter is called ……………. in CE arrangement with output shorted

Voltage gain
Current gain
Input impedance
None of the above
Ans : 2

If the operating point changes, the h parameters of transistor ………..

Also change
Do not change
May or may not change
None of the above
Ans : 1

The values of h parameter of a transistor in CE arrangement are ……………… arrangement

The same as for CB
The same as for CC
Different from that in CB
None of the above
Ans : 3

In order to determine hfe and hie parameters of a transistor, ………… is an a.c. short-circuited

Input
Output
Input as well as output
None of the above
Ans : 2

If temperature changes, h parameters of a transistor ………….

May or may not change
Do not change
Also change
None of the above
Ans : 3

In CE arrangement, the value of input impedance is approximately equal to …………..

Hie
Hoe
Hre
None of the above
Ans : 1

ELECTRONIC INSTRUMENTS

An ammeter is connected in …………….. with the circuit element whose current we wish to measure
Series
Parallel
Series or parallel
None of the above
Ans : 1
A galvanometer in series with a high resistance is called ……………
An ammeter
A voltmeter
A wattmeter
None of the above
Ans : 2
An ammeter should have ………….. resistance
Infinite
Very large
Very low
None of the above
Ans : 3
A voltmeter is connected in a ………….. with the circuit component across which potential difference is to be measured
Parallel
Series
Series or parallel
None of the above
Ans : 1
A voltmeter should have ………. resistance
Zero
Very high
Very low
None of the above
Ans : 2
The sensitivity of a multimeter is given in ……………..

O
Amperes
kO/V
none of the above
Ans : 3

If the full-scale deflection current of a multimeter is 50 µA, its sensitivity is ……..

10 kO/V
100 kO/V
50 kO/V
20 kO/V
Ans : 4

If a multimeter has a sensitivity of 1000 O per volt and reads 50 V full scale, its internal resistance is ………..

20 kO
50 kO
10 kO
None of the above
Ans : 2

A VTVM has ………. input resistance than that of a multimeter

More
Less
Same
None of the above
Ans : 1

The input resistance of a VTVM is about ………..

1000 O
10 kO
20 kO
10 MO
Ans : 4

If the negative potential on the control grid of CRT is increased, the intensity of spot ………….

Is increased
Is decreased
Remains the same
None of the above
Ans : 2

For display of signal pattern ………… voltage is applied to the horizontal plates of a CRO

Sinusoidal
Rectangular
Sawtooth
None of the above
Ans : 3

Two multimeters A and B have sensitivities of 10 kO/V and 30 kO/V respectively. Then …………..

Multimeter A is more sensitive
Multimeter B is more sensitive
Both are equally sensitive
None of the above
Ans : 2

A galvanometer of resistance G is shunted by a very small resistance S. The resistance of the resulting ammeter is ………………

GS/(G+S)
G+S
G-S
None of the above
Ans : 1

A VTVM is never used to measure …………..

Voltage
Current
Resistance
None of the above
Ans : 2

The sensitivity of a voltmeter which uses a 100 µA meter movement is ……………..

1 kO/V
10 kO/V
5 kO/V
Data insufficient
Ans : 2

What is the total resistance of a voltmeter on the 10 V range when the meter movement is rated for 50 µA of full-scale current?

10 kO
20 kO
200 kO
None of the above
Ans : 3

The materil used to coat inside the face of CRT is …………..

Carbon
Sulphur
Silicon
Phosphorous
Ans : 4

When an ammeter is inserted in the circuit, the circuit current will ………..

Increase
Decrease
Remain the same
None of the above
Ans : 2

A series ohmmeter circuit uses a 3 V battery and a 1 mA meter movement. What is the half-scale resistance for this movement?

3 kO
kO
kO
6 kO
Ans : 1

The most accurate device for measuring voltage is ………….

Voltmeter
Multimeter
CRO
VTVM
Ans : 3

The horizontal plates of a CRO are supplied with …………. to observe the waveform of signal.

Sinusoidal wave
Cosine wave
Sawtooth wave
None of the above
Ans : 3

A CRO is used to measure ………….

Voltage
Frequency
Phase
All of above
Ans : 4

If 2% of the main current is to be passed through a galvanometer of resistance G, then resistance of the shunt required is ……….

G/50
G/49
49 G
50 G
Ans : 2

Which of the following is likely to have the largest resistance?

Voltmeter of range 10 V
Moving coil galvanometer
Ammeter of range 1 A
A copper wire of length 1 m and diameter 3 mm
Ans : 1

An ideal ammeter has ………… resistance

Low
Infinite
Zero
High
Ans : 3

The resistance of an ideal voltmeter is …………

Low
Infinite
Zero
High
Ans : 2

To send 10% of the main current through a moving coil galvanometer of resistance 99 O the shunt required is …………..

11 O
9 O
100 O
9 O
Ans : 1

A voltmeter has a resistance of G ohms and range V volts. The value of resistance required in series to convert it into voltmeter of range nV is ……………

nG
G/n
G/(n-1)
(n-1)G
Ans : 4

An ammeter has a resistance of G ohms and range of I amperes. The value of resistance required in parallel to convert it into an ammeter of range nI is ………….

nG
(n-1)G
G/(n-1)
G/n
Ans : 3

INTEGRATED CIRCUITS

An IC has …………….. size
Very large
Large
Extremely small
None of the above
Ans : 3
ICs are generally made of ………………
Silicon
Germanium
Copper
None of the above
Ans : 1
……………… ICs are the most commonly used

Thin films
Monolithic
Hybrid
None of the above
Ans : 2

The most popular form of IC package is ……………..

DIL
Flatpack
TO-5
None of the above
Ans : 2

……………. cannot be fabricated on an IC

Transistors
Diodes
Resistors
Large inductors and transformers
Ans : 4

An audio amplifier is an example of ………………

Digital IC
Linear IC
Both digital and linear IC
None of the above
Ans : 2

The active components in an IC are ………….

Resistors
Capacitors
Transistors and diodes
None of the above
Ans : 3

We use ……………….. ICs in computers

Digital
Linear
Both digital and linear
None of the above
Ans : 1

The SiO2 layer in an IC acts as ………….

A resistor
An insulating layer
Mechanical output
None of the above
Ans : 2

ICs are used in ……………

Linear devices only
Digital devices only
Both linear and digital devices
None of the above
Ans : 3

A transistor takes …………… inductor on a silicon IC chip

Less space than
More space than
Same space as
None of the above
Ans : 1

The most popular types of ICs are …………..

Thin-film
Hybrid
Thick-film
Monolithic
Ans : 4

Digital ICs process …………….

Linear signals only
Digital signals only
Both digital and linear signals
None of the above
Ans : 3

Operational amplifiers use …………..

Linear ICs
Digital ICs
Both linear and digital ICs
None of the above
Ans : 2

Which of the following is most difficult to fabricate in an IC?

Diode
Transistor
FET
Capacitor
Ans : 4

POWER ELECTRONICS

A Triac has three terminals viz ………………
Drain, source, gate
Two main terminal and a gate terminal
Cathode, anode, gate
None of the above
Ans : 2
A triac is equivalent to two SCRs …………..
In parallel
In series
In inverse-parallel
None of the above
Ans : 3
A triac is a …………. switch
Bidirectional
Unidirectional
Mechanical
None of the above
Ans : 1
The V-I characteristics for a triac in the first and third quadrants are essentially identical to those of ………………. in its first quadrant
Transistor
SCR
UJT
none of the above
Ans : 2
A triac can pass a portion of …………… half-cycle through the load
Only positive
Only negative
Both positive and negative
None of the above
Ans : 3
A diac has ………….. terminals
Two
Three
Four
None of the above
Ans : 1
A triac has …………….. semiconductor layers
Two
Three
Four
Five
Ans : 3
A diac has …………… pn junctions
Four
Two
Three
None of the above
Ans : 2
The device that does not have the gate terminal is ……………….
Triac
FET
SCR
Diac
Ans : 4
A diac has ……………… semiconductor layers
Three
Two
Four
None of the above
Ans : 1
A UJT has ……………….
Two pn junctions
One pn junction
Three pn junctions
None of the above
Ans : 2
The normal way to turn on a diac is by ………………..
Gate current
Gate voltage
Breakover voltage
None of the above
Ans : 3
A diac is …………………. switch
An c.
A d.c.
A mechanical
None of the above
Ans : 1
In a UJT, the p-type emitter is ……………. doped
Lightly
Heavily
Moderately
None of the above
Ans : 2
Power electronics essentially deals with control of a.c. power at …………
Frequencies above 20 kHz
Frequencies above 1000 kHz
Frequencies less than 10 Hz
50 Hz frequency
Ans : 4
When the emitter terminal of a UJT is open, the resistance between the base terminal is generally ………………..
High
Low
Extremely low
None of the above
Ans : 1
When a UJT is turned ON, the resistance between emitter terminal and lower base terminal …………….
Remains the same
Is decreased
Is increased
None of the above
Ans : 2
To turn on UJT, the forward bias on the emitter diode should be …………… the peak point voltage
Less than
Equal to
More than
None of the above
Ans : 3
A UJT is sometimes called …………. diode
Low resistance
High resistance
Single-base
Double-base
Ans : 4
When the temperature increases, the inter-base resistance (RBB) of a UJT ………….
Increases
Decreases
Remains the same
None of the above
Ans : 1
When the temperature increases, the intrinsic stand off ratio ……….
Increases
Decreases
Essentially remains the same
None of the above
Ans : 3
Between the peak point and the valley point of UJT emitter characteristics we have ………….. region
Saturation
Negative resistance
Cut-off
None of the above
Ans : 2
A diac is turned on by …………………
A breakover voltage
Gate voltage
Gate current
None of the above
Ans : 1
The device that exhibits negative resistance region is ………………..
Diac
Triac
Transistor
UJT
Ans : 4
The UJT may be used as ……………….
Am amplifier
A sawtooth generator
A rectifier
None of the above
Ans : 2
A diac is simply ………………
A single junction device
A three junction device
A triac without gate terminal
None of the above
Ans : 3
After peak point, the UJT operates in the ……………. region
Cut-off
Saturation
Negative resistance
None of the above
Ans : 3
Which of the following is not a characteristic of UJT?
Intrinsic stand off ratio
Negative resistance
Peak-point voltage
Bilateral conduction
Ans : 4
The triac is …………….
Like a bidirectional SCR
A four-terminal device
Not a thyristor
Answers (1) and (2)
Ans : 1

SILICON CONTROLLED RECTIFIERS

An SCR has …………….. pn junctions
Two
Three
Four
None of the above
ANS : 2
An SCR is a solid state equivalent of …………….
Triode
Pentode
Gas-filled triode
Tetrode
ANS : 3
An SCR has ………….. semiconductor layers
Two
Three
Four
None of the above
ANS : 3
An SCR has three terminals viz ……………
Cathode, anode, gate
Anode, cathode, grid
Anode, cathode, drain
None of the above
ANS : 1
An SCR behaves as a ……………. switch
Unidirectional
Bidirectional
Mechanical
None of the above
ANS : 1
An SCR is sometimes called …………
Triac
Diac
Unijunction transistor
Thyristor
ANS : 4
An SCR is made of ………….
Germanium
Silicon
Carbon
None of the above
ANS : 2
In the normal operation of an SCR, anode is …………… w.r.t. cathode
At zero potential
Negative
Positive
None of the above
ANS : 3
In normal operation of an SCR, gate is ………..w.r.t. cathode
Positive
Negative
At zero potential
None of the above
ANS : 1
An SCR combines the features of …………..
A rectifier and resistance
A rectifier and transistor
A rectifier and capacitor
None of the above
ANS : 2
The control element of an SCR is ………….

Cathode
Anode
Anode supply
Gate
ANS : 4

The normal way to turn on a SCR is by ……………..

Breakover voltage
Appropriate anode current
Appropriate gate current
None of the above
ANS : 3

An SCR is turned off by …………….

Reducing anode voltage to zero
Reducing gate voltage to zero
Reverse biasing the gate
None of the above
ANS : 1

An SCR is a ……………….. triggered device

Voltage
Current
Voltage as well as current
None of the above
ANS : 2

In an SCR circuit the supply voltage is generally ……….. that of breakover voltage

Equal to
Less than
Greater than
None of the above
ANS : 2

When an SCR is turned on, the voltage across it is about ……….

Zero
10 V
1 V
1 V
ANS : 4

An SCR is made of silicon and not germanium because silicon ………

Is inexpensive
Is mechanically strong
Has small leakage current
Is tetravalent
ANS : 3

An SCR is turned off when …………..

Anode current is reduced to zero
Gate voltage is reduced to zero
Gate is reverse biased
None of the above
ANS : 1

In an SCR circuit, the angle of conduction can be changed by ……….

Changing anode voltage
Changing gate voltage
Reverse biasing the gate
None of the above
ANS : 2

If firing angle in an SCR circuit is increased, the output …………

Remains the same
Is increased
Is decreased
None of the above
ANS : 3

If gate current is increased, then anode-cathode voltage at which SCR closes …………….

Is decreased
Is increased
Remains the same
None of the above
ANS : 1

When SCR is OFF, the current in the circuit is …………….

Exactly zero
Small leakage current
Large leakage current
None of the above
ANS : 2

An SCR can exercise control over ………. of a.c. supply

Positive half-cycles only
Negative half-cycles only
Both positive and negative half-cycles
Positive or negative half-cycles
ANS : 4

We can control a.c. power in a load by connecting …………

Two SCRs in series
Two SCRs in parallel
Two SCRs in parallel opposition
None of the above
ANS : 3

When SCR starts conducting, then ……………. loses all control

Gate
Cathode
Anode
None of the above
ANS : 1

FET

A JFET has three terminals, namely …………
cathode, anode, grid
emitter, base, collector
source, gate, drain
none of the above
Ans : 3
A JFET is similar in operation to …………. valve
diode
pentode
triode
tetrode
Ans : 2
A JFET is also called …………… transistor
unipolar
bipolar
unijunction
none of the above
Ans : 1
A JFET is a ………… driven device
current
voltage
both current and voltage
none of the above
Ans : 2
The gate of a JFET is ………… biased
reverse
forward
reverse as well as forward
none of the above
Ans : 1
The input impedance of a JFET is …………. that of an ordinary transistor
equal to
less than
more than
none of the above
Ans : 3
In a p-channel JFET, the charge carriers are …………..
electrons
holes
both electrons and holes
none of the above
Ans : 2
When drain voltage equals the pinch-off-voltage, then drain current …………. with the increase in drain voltage
decreases
increases
remains constant
none of the above
Ans : 3
If the reverse bias on the gate of a JFET is increased, then width of the conducting channel …………..
is decreased
is increased
remains the same
none of the above
Ans : 1
A MOSFET has …………… terminals
two
five
four
three
Ans : 4
A MOSFET can be operated with ……………..

negative gate voltage only
positive gate voltage only
positive as well as negative gate voltage
none of the above
Ans : 3

A JFET has ……….. power gain

small
very high
very small
none of the above
Ans : 2

The input control parameter of a JFET is ……………

gate voltage
source voltage
drain voltage
gate current
Ans : 1

A common base configuration of a pnp transistor is analogous to ………… of a JFET

common source configuration
common drain configuration
common gate configuration
none of the above
Ans : 3

A JFET has high input impedance because …………

it is made of semiconductor material
input is reverse biased
of impurity atoms
none of the above
Ans : 2

In a JFET, when drain voltage is equal to pinch-off voltage, the depletion layers ………

almost touch each other
have large gap
have moderate gap
none of the above
Ans : 1

In a JFET, IDSS is known as …………..

drain to source current
drain to source current with gate shorted
drain to source current with gate open
none of the above
Ans : 2

The two important advantages of a JFET are …………..

high input impedance and square-law property
inexpensive and high output impedance
low input impedance and high output impedance
none of the above
Ans : 1

…………. has the lowest noise-level

triode
ordinary trnsistor
tetrode
JFET
Ans : 4

A MOSFET is sometimes called ………. JFET

many gate
open gate
insulated gate
shorted gate
Ans : 3

Which of the following devices has the highest input impedance?

JFET
MOSFET
Crystal diode
ordinary transistor
Ans : 2

A MOSFET uses the electric field of a ………. to control the channel current

capacitor
battery
generator
none of the above
Ans : 1

The pinch-off voltage in a JFET is analogous to ………. voltage in a vacuum tube

anode
cathode
grid cut off
none of the above
Ans : 3

In class A operation, the input circuit of a JFET is ………. biased

forward
reverse
not
none of the above
Ans : 2

If the gate of a JFET is made less negative, the width of the conducting channel……….

remains the same
is decreased
is increased
none of the above
Ans : 3

The pinch-off voltage of a JFET is about ……….

5 V
0.6 V
15 V
25 V
Ans : 1

The input impedance of a MOSFET is of the order of ………..

O
a few hundred O
kO
several MO
Ans : 4

The gate voltage in a JFET at which drain current becomes zero is called ……….. voltage

saturation
pinch-off
active
cut-off
Ans : 2

In a FET, there are ……….. pn junctions at the sides

three
four
five
two
Ans : 4

The transconductance of a JFET ranges from ……………..

100 to 500 mA/V
500 to 1000 mA/V
0.5 to 30 mA/V
above 1000 mA/V
Ans : 3

The source terminal of a JEFT corresponds to ………….. of a vacuum tube

plate
cathode
grid
none of the above
Ans : 2

The output characteristics of a JFET closely resemble the output characteristics of a ………. valve

pentode
tetrode
triode
diode
Ans : 1

If the cross-sectional area of the channel in n-channel JEFT increases, the drain current ……….

is increased
is decreased
remains the same
none of the above
Ans : 1

The channel of a JFET is between the …………….

gate and drain
drain and source
gate and source
input and output
Ans : 2

For VGS = 0 V, the drain current becomes constant when VDS exceeds ………

cut off
VDD
VP
o V
Ans : 3

A certain JFET data sheet gives VGS(off) = -4 V. The pinch-off voltage Vp is ……..

+4 V
-4 V
dependent on VGS
data insufficient
Ans : 1

The constant-current region of a JFET lies between

cut off and saturation
cut off and pinch-off
o and IDSS
pinch-off and breakdown
Ans : 4

At cut-off, the JFET channel is ……….

at its widest point
completely closed by the depletion region
extremely narrow
reverse baised
Ans : 2

A MOSFET differs from a JFET mainly because ………………

of power rating
the MOSFET has two gates
the JFET has a pn junction
none of the above
Ans : 3

A certain D-MOSFET is biased at VGS = 0 V. Its data sheet specifies IDSS = 20mA and VGS(off) = -5 V. The value of the drain current is …………

20 mA
0 mA
40 mA
10 mA
Ans : 1

A n-channel D-MOSFET with a positive VGS is operating in …………

the depletion-mode
the enhancement-mode
cut off
saturation
Ans : 2

A certain p-channel E-MOSFET has VGS(th) = -2V. If VGS= 0V, the drain current is ……….

0 mA
ID(on)
maximum
IDSS
Ans : 1

In a common-source JFET amplifier, the output voltage is …………………

180o out of phase with the input
in phase with the input
90o out of phase with the input
taken at the source
Ans : 1

In a certain common-source D-MOSFET amplifier, Vds =3.2 V r.m. and Vgs = 280 mV r.m.s. The voltage gain is …………

1
11.4
8.75
3.2
Ans : 2

In a certain CS JFET amplifier, RD= 1kO , RS= 560 O , VDD=10V and gm= 4500 µS. If the source resistor is completely bypassed, the voltage gain is …………

450
45
2.52
4.5
Ans : 4

A certain common-source JFET has a voltage gain of 10. If the source bypass capacitor is removed, ……………….

the voltage gain will increase
the transconductance will increase
the voltage gain will decrease
the Q-point will shift
Ans : 3

A CS JFET amplifier has a load resistance of 10 kO , RD= 820O . If gm= 5mS and Vin= 500 mV, the output signal voltage is ………..

2.05 V
25 V
0.5 V
1.89 V
Ans : 4

If load resistance in the above question (Q.49) is removed, the output voltage will …………
increase
decrease
stay the same
be zero
Ans : 1

SOLID STATE SWITCHING CIRCUITS

A switch has ………………
One state
Two states
Three states
None of the above
Ans : 2
A relay is ……….. switch
A mechanical
An electronic
An electromechanical
None of the above
Ans : 3
The switch that has the fastest speed of operation is ………….. switch
Electronic
Mechanical
Electromechanical
None of the above
Ans : 1
The most inexpensive switch is ………….. switch
Electronic
Mechanical
Electromechanical
None of the above
Ans : 1
The main disadvantage of a mechanical switch is that it………….
Is operated mechanically
Is costly
Has high inertia
None of the above
Ans : 3
When a transistor is driven to saturation, ideally the output is ………………
VCC
0
VCC/2
2VCC
Ans : 2
The maximum speed of electronic switch can be ………….. operations per second

104
10
1000
109
Ans : 4

A relay is superior to a mechanical switch because it ……………

Is relatively inexpensive
Does not require moving contacts
Combines control with power amplification
None of the above
Ans : 3

When a transistor is driven to cut off, ideally the output is …………..

VCC
0
VCC/2
VCC/3
Ans : 1

………………. multivibrator is a square wave oscillator

Monostable
Astable
Bistable
None of the above
Ans : 2

An astable multivibrator has ………….

One stable state
Two stable states
No stable state
None of the above
Ans : 3

If d.c. supply of 10 V is fed to a differentiating circuit, then output will be …….

20 V
10 V
0 V
None of the above
Ans : 3

If the input to a differentiating circuit is a saw-tooth wave, then output will be ………….

Square
Triangular
Sine
Rectangular
Ans : 4

A bistable multivibrator has …………..

Two stable states
One stable state
No stable state
None of the above
Ans : 1

If a square wave is fed to a differentiating circuit, the output will be …………

Sine wave
Sharp narrow pulses
Rectangular wave
Triangular wave
Ans : 2

An integrating circuit is a simple RC series circuit with output taken across ………

Both R and C
R
C
None of the above
Ans : 3

For an integrating circuit to be effective , the RC product should be ………. the time period of the input wave

5 times greater than
5 times smaller than
Equal to
At least 10 times greater than
Ans : 4

A differentiating circuit is a simple RC circuit with output taken across …………..

R
C
Both R and C
None of the above
Ans : 1

A monostable vibrator has …………..

No stable state
One stable state
Two stable states
None of the above
Ans : 2

The multivibrator which generates square wave of its own is the ………… multivibrator

Monostable
Bistable
Astable
None of the above
Ans : 3

For a differentiating circuit to be effective, the RC product should be ………… the time period of the input wave

Equal to
5 times greater than
5 times smaller than
At least 10 times greater than
Ans : 4

When a rectangular voltage waveform is applied to a capacitor, then the current waveform is ……………

Rectangular
Sinusoidal
Sawtooth
Square
Ans : 1

The positive clipper is that which removes the …………………. half-cycles of the input voltage.

Negative
Positive
Both positive and negative
None of the above
Ans : 2

A clamping circuits adds ………………… component to the signal

c.
c.
both d.c. and a.c.
none of the above
Ans : 1

One would find a clamping circuit in ………………..

Receiving antenna
Radio transmitter
Radio receiver
Television receiver
Ans : 4

When a transistor is used as an amplifier, it is operated in the ……………… region

Off
Saturation
Active
None of the above
Ans : 3

When the transistor (CE arrangement) is in the cut off region, the collector current is ……………..

ICBO
ICEO
(ß + 1) ICEO
IC(sat)
Ans : 2

A negative clipper removes the ……………… half-cycles of the input voltage

Negative
Positive
Both positive and negative
None of the above
Ans : 1

If the input to an integrating circuit is a succession of alternating positive and negative pulses of very short duration, the output will be …………… wave

Rectangular
Triangular
Sine
Square
Ans : 4

In a multivibrator, we have ………. feedback.
Negative
100 % positive
Both positive and negative
None of the above
Ans : 2

REGULATED D.C. POWER SUPPLY

In an unregulated power supply, if load current increases, the output voltage ………..
Remains the same
Decreases
Increases
None of the above
Ans : 2
In an unregulated power supply, if input a.c. voltage increases, the output voltage …….
Increases
Decreases
Remains the same
None of the above
Ans : 1
A power supply which has voltage regulation of ……….. is unregulated power supply
0 %
5 %
10 %
8%
Ans : 3
Commercial power supplies have voltage regulation ………….
of 10%
of 15%
of 25%
within 1%
Ans : 4
An ideal regulated power supply is one which has voltage regulation of …………
0%
5%
10%
1%
Ans : 1
A Zener diode utilises ………… characteristic for voltage regulation

Forward
Reverse
Both forward and reverse
None of the above
Ans : 2

Zener diode can be used as …………
voltage regulator only
c. voltage regulator only
both d.c. and a.c. voltage regulator
none of the above
Ans : 3
A Zener diode is used as a …………… voltage regulating device

Shunt
Series
Series-shunt
None of the above
Ans : 1

As the junction temperature increases, the voltage breakdown point for Zener mechanism …………

Is increased
Is decreased
Remains the same
None of the above
Ans : 2

The rupture of co-valent bonds will occur when the electric field is ………….

100 V/cm
6 V/cm
1000 V/cm
More than 105 V/cm
Ans : 4

In a 15 V Zener diode , the breakdown mechanism will occur by ………….

Avalanche mechanism
Zener mechanism
Both Zener and avalanche mechanism
None of the above
Ans : 1

A Zener diode that has very narrow depletion layer will breakdown by ……… mechanism

Avalanche
Zener
Both avalanche and Zener
None of the above
Ans : 2

As the junction temperature increases, the voltage breakdown point for avalanche mechanism ………….

Remains the same
Decrease
Increases
None of the above
Ans : 3

Another name for Zener diode is ………… diode

Breakdown
Voltage
Power
Current
Ans : 1

Zener diode are generally made of ……….

Germanium
Silicon
Carbon
None of the above
Ans : 2

For increasing the voltage rating, zeners are connected in …………..

Parallel
Series-parallel
Series
None of the above
Ans : 3

In a Zener voltage regulator, the changes in load current produce changes in …………….

Zener current
Zener voltage
Zener voltage as well as Zener current
None of the above
Ans : 1

A Zener voltage regulator is used for …………… load currents

High
Very high
Moderate
Small
Ans : 4

A Zener voltage regulator will cease to act as a voltage regulator if Zener current becomes ……………

Less than load current
Zero
More than load current
None of the above
Ans : 2

If the doping level is increased, the breakdown voltage of the Zener …………..

Remains the same
Is increased
Is decreased
None of the above
Ans : 3

A 30 V Zener will have depletion layer width …………. that of 10 V Zener

More than
Less than
Equal to
None of the above
Ans : 1

The current in a Zener diode is limited by …………..

External resistance
Power dissipation
Both (1) and (2)
None of the above
Ans : 3

A 5 mA changes in Zener current produces a 50 mA change in Zener voltage. What is the Zener impedance?

1 O
1 O
100 O
10 O
Ans : 4

A certain regulator has a no-load voltage of 6 V and a full-load output of 5.82 V. What is the load regulation?

09%
87 %
72 %
None of the above
Ans : 1

What is true about the breakdown voltage in a Zener diode?

It decreases when load current increases
It destroys the diode
It equals current times the resistance
It is approximately constant
Ans : 4

Which of these is the best description for a Zener diode?

It is a diode
It is a constant current device
It is a constant-voltage device
It works in the forward region
Ans : 3

A Zener diode …………..

Is a battery
Acts like a battery in the breakdown region
Has a barrier potential of 1 V
Is forward biased
Ans : 2

The load voltage is approximately constant when a Zener diode is ……….

Forward biased
Unbiased
Reverse biased
Operating in the breakdown region
Ans : 4

In a loaded Zener regulator, which is the largest Zener current?

Series current
Zener current
Load current
None of the above
Ans : 1

If the load resistance decreases in a Zener regulator, then Zener current …………….

Decreases
Stays the same
Increases
None of the above
Ans : 1

If the input a.c. voltage to regulated or ordinary power supply increases by 5% what will be the approximate change in d.c. output voltage?

10%
20%
15%
5%
Ans : 4

If the load current drawn by unregulated power supply increases, the d.c. output voltage ………..

Increases
Decreases
Stays the same
None of the above
Ans : 2

If the load current drawn by unregulated power supply increases, the d.c. output voltage ………

Increases
Decreases
Stays the same
None of the above
Ans : 2

A power supply has a voltage regulation of 1%. If the no-load voltage is 20 V, what is the full-load voltage?

8 V
7 V
6 V
2 V
Ans : 1

Two similar 15 V Zeners are connected in series. What is the regulated output voltage?

15 V
5 V
30 V
45 V
Ans : 3

A power supply can deliver a maximum rated current of 0.5 A at full-load output voltage of 20 V. What is the minimum load resistance that you can connect across the supply?

10 O
20 O
15 O
40 O
Ans : 4

In a regulated power supply, two similar 15 V zeners are connected in series. The input voltage is 45 V d.c. If each Zener has a maximum current rating of 300 mA, what should be the value of the series resistance?

10 O
50 O
25 O
40 O
Ans : 2

A Zener regulator …………… in the power supply

Increases the ripple
Decreases the ripple
Neither increases nor decreases the ripple
Data insufficient
Ans : 2

When load current is zero, the Zener current will be ………

Zero
Minimum
Maximum
None of the above
Ans : 3

The Zener current will be minimum when …………

Load current is maximum
Load current is minimum
Load current is zero
None of the above
Ans : 1

MODULATION & DEMODULATION

Modulation is done in …………..
Transmitter
Radio receiver
Between transmitter and radio receiver
None of the above
Answer : 1
In a transmitter ……………. oscillator is used
Hartley
RC phase-shift
Wien-bridge
Crystal
Answer : 4
In India, ……………. modulation is used for radio transmission
Frequency
Amplitude
Phase
None of the above
Answer : 2
In an AM wave useful power is carrier by ………….
Carrier
Sidebands
Both sidebands and carrier
None of the above
Answer : 2
In amplitude modulation, bandwidth is ……………. the audio signal frequency
Thrice
Four times
Twice
None of the above
Answer : 3
In amplitude modulation, the ………… of carrier is varied according to the strength of the signal.

Amplitude
Frequency
Phase
None of the above
Answer : 1

Overmodulation (amplitude) occurs when signal amplitude is …………. carrier amplitude

Equal to
Greater than
Less than
None of the above
Answer : 2

In an AM wave, the majority of the power is in …………….

Lower sideband
Upper sideband
Carrier
None of the above
Answer : 3

At 100% modulation, the power in each sideband is ………………… of that of carrier

50%
40%
60%
25%
Answer : 4

Overmodulation results in …………..

Weakening of the signal
Excessive carrier power
Distortion
None of the above
Answer : 3

If modulation is 100% then signal amplitude is ………….. carrier amplitude

Equal to
Greater than
Less than
None of the above
Answer : 1

As the modulation level is increased, the carrier power …………..

Is increased
Remains the same
Is decreased
None of the above
Answer : 2

Demodulation is done in …………

Receiving antenna
Transmitter
Radio receiver
Transmitting antenna
Answer : 3

A high Q tuned circuit will permit an amplifier to have high ……………

Fidelity
Frequency range
Sensitivity
Selectivity
Answer : 4

In radio transmission, the medium of transmission is ……………..

Space
An antenna
Cable
None of the above
Answer : 1

If level of modulation is increased ……………. power is increased

Carrier
Sideband
Carrier as well as sideband
None of the above
Answer : 2

In TV transmission, picture signal is ……………… modulated

Frequency
Phase
Amplitude
None of the above
Answer : 3

In a radio receiver, noise is generally developed at ………….

IF stage
Receiving antenna
Audio stage
RF stage
Answer : 4

Man made noise are …………. variations.

Amplitude
Frequency
Phase
Both phase and frequency
Answer : 1

The signal voltage induced in the aerial of a radio receiver is of the order of …………….

mV
µV
V
None of the above
Answer : 2

Superhertodyne principle refers to

Using a large number of amplifier stages
Using a push-pull circuit
Obtaining lower fixed intermediate frequency
None of the above
Answer : 3

If a radio receiver amplifies all the signal frequencies equally well, it is said to have high …………

Sensitivity
Selectivity
Distortion
Fidelity
Answer : 4

Most of the amplification in a superhetrodyne receiver occurs at ………. stage

IF
RF amplifier
Audio amplifier
Detector
Answer : 1

The letters AVC stand for …………..

Audio voltage control
Abrupt voltage control
Automatic volume control
Automatic voltage control
Answer : 3

The superhetrodyne principle provides selectivity at ………. stage

RF
IF
audio
Before RF
Answer : 2

In superhetrodyne receiver, the input at mixer stage is ……….

IF and RF
RF and AF
IF and AF
RF and local oscillator signal
Answer : 4

The major advantage of FM over AM is …………..

Reception is less noisy
Higher carrier frequency
Smaller bandwidth
Small frequency deviation
Answer : 1

When the modulating signal controls the frequency of the carrier, we get……….

Phase modulation
Amplitude modulation
Frequency modulation
May be any one of the above
Answer : 3

Modulation refers to a low-frequency signal controlling the …………

Amplitude of the carrier
Frequency of the carrier
Phase of the carrier
May be any of the above
Answer : 4

The IF is 455 kHz. If the radio receiver is tuned to 855 kHz, the local oscillator frequency is ………….

455 kHz
1310 kHz
1500 kHz
1520 kHz
Answer : 2

If Amin = 40 and Amax = 60, what is the percentage of modulation?

20 %
40 %
50 %
10 %
Answer : 1

The function of ferrite antenna is to …………….

Reduce stray capacitance
Stabilise d.c. bias
Increase the Q of tuned circuit
Reduce noise
Answer : 3

In a radio receiver, we generally use ………….. oscillator as a local oscillator

Crystal
Wien-bridge
Phase-shift
Hartley
Answer : 4

A 100 V carrier is made to vary between 160 V and 40 V by the signal. What is the modulation factor?

3
6
5
None of the above
Answer : 2

A 50 kW carrier is to be amplitude modulated to a level of 85%. What is the carrier power after modulation?

50 kW
5 kW
8 kW
25 kW
Answer : 1

In the above question, what is the power in sidebands?

8 kW
6 kW
06 kW
9 kW
Answer : 3

In a superhetrodyne receiver, the difference frequency is chosen as the IF rather than the sum frequency because …………….

The difference frequency is closer to oscillator frequency
Lower frequencies are easier to amplify
Only the difference frequency can be modulated
None of the above
Answer : 2

The diode detector in an AM radio receiver is usually found ………….

Before the first RF stage
After the first RF stage
After several stages of amplification
None of the above
Answer : 3

In a TRF radio receiver, the RF and detection stages are tuned to …………

Radio frequency
IF
Audio frequency
None of the above
Answer : 1

In TV transmission, sound signal is ………………… modulated

Amplitude
Frequency
Phase
None of the above
Answer : 2

TRANSISTOR TUNED AMPLIFIERS

A tuned amplifier uses ……………. load
Resistive
Capacitive
LC tank
Inductive
Ans : 3
A tuned amplifier is generally operated in ……………. operation
Class A
Class C
Class B
None of the above
Ans : 2
A tuned amplifier is used in …………… applications
Radio frequency
Low frequency
Audio frequency
None of the above
Ans : 1
Frequencies above …………… kHz are called radio frequencies
2
10
50
200
Ans : 4
At series or parallel resonance, the circuit power factor is …………..
0
5
1
8
Ans : 3
The voltage gain of a tuned amplifier is ……………. at resonant frequency

Minimum
Maximum
Half-way between maximum and minimum
Zero
Ans : 2

At parallel resonance, the line current is ……………….

Minimum
Maximum
Quite large
None of the above
Ans : 1

At series resonance, the circuit offers …………….. impedance

Zero
Maximum
Minimum
None of the above
Ans : 3

A resonant circuit contains ……………… elements

R and L only
R and C only
Only R
L and C
Ans : 4

At series or parallel resonance, the circuit behaves as a …………….. load

Capacitive
Resistive
Inductive
None of the above
Ans : 2

At series resonance, voltage across L is ………………. voltage across C

Equal to but opposite in phase to
Equal to but in phase with
Greater than but in phase with
Less than but in phase with
Ans : 1

When either L or C is increased, the resonant frequency of LC circuit ……………

Remains the same
Increases
Decreases
Insufficient data
Ans : 3

At parallel resonance, the net reactive component circuit current is …………

Capacitive
Zero
Inductive
None of the above
Ans : 2

In parallel resonance, the circuit impedance is …………..

C/LR
R/LC
CR/L
L/CR
Ans : 4

In a parallel LC circuit, if the input signal frequency is increased above resonant frequency then …………………..

XL increases and XC decreases
XL decreases and XC increases
Both XL and XC increase
Both XL and XC decrease
Ans : 1

The Q of an LC circuit is given by ………………….

2pfr x R
R / 2pfrL
2pfrL / R
R2/2pfrL
Ans : 3

If Q of an LC circuit increases, then bandwidth …………………

Increases
Decreases
Remains the same
Insufficient data
Ans : 2

At series resonance, the net reactive component of circuit current is ……………….

Zero
Inductive
Capacitive
None of the above
Ans : 1

The dimensions of L/CR are that of …………….

Farad
Henry
Ohm
None of the above
Ans : 3

If L/C ratio of a parallel LC circuit is increased, the Q of the circuit ……………..

Is decreased
Is increased
Remains the same
None of the above
Ans : 2

At series resonance, the phase angle between applied voltage and circuit is ………..

90o
180o
0o
None of the above
Ans : 3

At parallel resonance, the ratio L/C is …………….

Very large
Zero
Small
None of the above
Ans : 1

If the resistance of a tuned circuit is increased, the Q of the circuit ………….

Is increased
Is decreased
Remains the same
None of the above
Ans : 2

The Q of a tuned circuit refers to the property of …………..

Sensitivity
Fidelity
Selectivity
None of the above
Ans : 3

At parallel resonance, the phase angle between the applied voltage and circuit current is …………….

90o
180o
0o
None of the above
Ans : 3

In a parallel LC circuit, if the signal frequency is decreased below the resonant frequency, then ……………

XL decreases and XC increases
XL increases and XC decreases
Line current becomes minimum
None of the above
Ans : 1

In series resonance, there is ………………

Voltage amplification
Current amplification
Both voltage and current amplification
None of the above
Ans : 1

The Q of a tuned amplifier is generally …………….

Less than 5
Less than 10
More than 10
None of the above
Ans : 3

The Q of a tuned amplifier is 50. If the resonant frequency for the amplifier is 1000kHZ, then bandwidth is …………

10kHz
40 kHz
30 kHz
20 kHz
Ans : 4

In the above question, what are the values of cut-off frequencies?

140 kHz , 60 kHz
1020 kHz , 980 kHz
1030 kHz , 970 kHz
None of the above
Ans : 2

For frequencies above the resonant frequency, a parallel LC circuit behaves as a ……………. load

Capacitive
Resistive
Inductive
None of the above
Ans : 1

In parallel resonance, there is …………

Both voltage and current amplification
Voltage amplifications
Current amplification
None of the above
Ans : 3

For frequencies below resonant frequency, a series LC circuit behaves as a ………… load

Resistive
Capacitive
Inductive
None of the above
Ans : 2

If a high degree of selectivity is desired, then double-tuned circuit should have …………. coupling

Loose
Tight
Critical
None of the above
Ans : 1

In the double tuned circuit, if the mutual inductance between the two tuned circuits is decreased, the level of resonance curve ………..

Remains the same
Is lowered
Is raised
None of the above
Ans : 3

For frequencies above the resonant frequency , a series LC circuit behaves as a ………….. load

Resistive
Inductive
Capacitive
None of the above
Ans : 2

Double tuned circuits are used in ……………. stages of a radio receiver

IF
Audio
Output
None of the above
Ans : 1

A class C amplifier always drives ………. load

A pure resistive
A pure inductive
A pure capacitive
A resonant tank
Ans : 4

Tuned class C amplifiers are used for RF signals of ………………

Low power
High power
Very high power
None of the above
Ans : 4

For frequencies below the resonant frequency , a parallel LC circuit behaves as a …………… load
Inductive
Resistive
Capacitive
None of the above
Ans : 1

OSCILLATORS

An oscillator converts ……………..
power into d.c. power
power into a.c. power
mechanical power into a.c. power
none of the above
Answer : 2
In an LC transistor oscillator, the active device is ……………
LC tank circuit
Biasing circuit
Transistor
None of the above
Answer : 3
In an LC circuit, when the capacitor is maximum, the inductor energy is ……….
Minimum
Maximum
Half-way between maximum and minimum
None of the above
Answer : 1
In an LC oscillator, the frequency of oscillator is ……………. L or C.
Proportional to square of
Directly proportional to
Independent of the values of
Inversely proportional to square root of
Answer : 4
An oscillator produces……………. oscillations
Damped
Undamped
Modulated
None of the above
Answer : 2
An oscillator employs ……………… feedback
Positive
Negative
Neither positive nor negative
Data insufficient
Answer : 1
An LC oscillator cannot be used to produce ……………….. frequencies
High
Audio
Very low
Very high
Answer : 3
Hartley oscillator is commonly used in ………………
Radio receivers
Radio transmitters
TV receivers
None of the above
Answer : 1
In a phase shift oscillator, we use …………. RC sections
Two
Three
Four
None of the above
Answer : 2
In a phase shift oscillator, the frequency determining elements are …………
L and C
R, L and C
R and C
None of the above
Answer : 3
A Wien bridge oscillator uses ……………. feedback
Only positive
Only negative
Both positive and negative
None of the above
Answer : 3
The piezoelectric effect in a crystal is ……………
A voltage developed because of mechanical stress
A change in resistance because of temperature
A change in frequency because of temperature
None of the above
Answer : 1
If the crystal frequency changes with temperature, we say that crystal has ………….. temperature coefficient
Positive
Zero
Negative
None of the above
Answer : 1
The crystal oscillator frequency is very stable due to ………………. of the crystal
Rigidity
Vibrations
Low Q
High Q
Answer : 4
The application where one would most likely find a crystal oscillator is ……………..
Radio receiver
Radio transmitter
AF sweep generator
None of the above
Answer : 2
An oscillator differs from an amplifier because it ………
Has more gain
Requires no input signal
Requires no d.c. supply
Always has the same input
Answer : 2
One condition for oscillation is ………….
A phase shift around the feedback loop of 180o
A gain around the feedback loop of one-third
A phase shift around the feedback loop of 0o
A gain around the feedback loop of less than 1
Answer : 3
A second condition for oscillations is ……………….
A gain of 1 around the feedback loop
No gain around the feedback loop
The attention of the feedback circuit must be one-third
The feedback circuit must be capacitive
Answer : 1
In a certain oscillator Av = 50. The attention of the feedback circuit must be …………
1
01
10
02
Answer : 4
For an oscillator to properly start, the gain around the feedback loop must initially be
1
Greater than 1
Less than 1
Equal to attenuation of feedback circuit
Answer : 2
In a Wien-bridge oscillator, if the resistances in the positive feedback circuit are decreased, the frequency……….
Remains the same
Decreases
Increases
Insufficient data
Answer : 3
In Colpitt’s oscillator, feedback is obtained …………….
By magnetic induction
By a tickler coil
From the centre of split capacitors
None of the above
Answer : 3
The Q of the crystal is of the order of …………
100
1000
50
More than 10,000
Answer : 4
Quartz crystal is most commonly used in crystal oscillators because ………….
It has superior electrical properties
It is easily available
It is quite inexpensive
None of the above
Answer : 1
………….. is a fixed frequency oscillator
Phase-shift oscillator
Hartely-oscillator
Colpitt’s oscillator
Crystal oscillator
Answer : 4
In an LC oscillator, if the value of L is increased four times, the frequency of oscillations is …………
Increased 2 times
Decreased 4 times
Increased 4 times
Decreased 2 times
Answer : 4
An important limitation of a crystal oscillator is ……………
Its low output
Its high Q
Less availability of quartz crystal
Its high output
Answer : 1
The signal generator generally used in the laboratories is ………….. oscillator
Wien-bridge
Hartely
Crystal
Phase shift
Answer : 1

Amplifiers with Negative Feedback Questions with Answers :-

When negative voltage feedback is applied to an amplifier, its voltage gain ……………….
Is increased
Is reduced
Remains the same
None of the above
Ansr : 2
The value of negative feedback fraction is always …………….
Less than 1
More than 1
Equal to 1
None of the above
Ansr : 1
If the output of an amplifier is 10 V and 100 mV from the output is fed back to the input, then feedback fraction is ………..
10
1
01
15
Ansr : 3
The gain of an amplifier without feedback is 100 db. If a negative feedback of 3 db is applied, the gain of the amplifier will become …………..
5 db
300 db
103 db
97 db
Ansr : 4
If the feedback fraction of an amplifier is 0.01, then voltage gain with negative feedback is approximately………..
500
100
1000
5000
Ansr : 2
A feedback circuit usually employs ……………… network

Resistive
Capacitive
Inductive
None of the above
Ansr : 1

The gain of an amplifier with feedback is known as ………….. gain

Resonant
Open loop
Closed loop
None of the above
Ansr : 3

When voltage feedback (negative) is applied to an amplifier, its input impedance ………….

Is decreased
Is increased
Remains the same
None of the above
Ansr : 2

When current feedback (negative) is applied to an amplifier, its input impedance …………..

Is decreased
Is increased
Remains the same
None of the above
Ansr : 1

Negative feedback is employed in ……………..

Oscillators
Rectifiers
Amplifiers
None of the above
Ansr : 3

Emitter follower is used for …………

Current gain
Impedance matching
Voltage gain
None of the above
Ansr : 2

The voltage gain of an emitter follower is ………..

Much less than 1
Approximately equal to 1
Greater than 1
None of the above
Ansr : 2

When current feedback (negative) is applied to an amplifier, its output impedance ……..

Is increased
Is decreased
Remains the same
None of the above
Ansr : 1

Emitter follower is a ……………….. circuit

Voltage feedback
Current feedback
Both voltage and current feedback
None of the above
Ansr : 1

If voltage feedback (negative) is applied to an amplifier, its output impedance …………..

Remains the same
Is increased
Is decreased
None of the above
Ansr : 3

When a negative voltage feedback is applied to an amplifier, its bandwidth……….
Is increased
Is decreased
Remains the same
Insufficient data
Ansr : 1
An emitter follower has ………… input impedance
Zero
Low
High
None of the above
Ansr : 3
The output impedance of an emitter follower is ……….
High
Very high
Almost zero
Low
Ansr : 4

PARALLEL CIRCUITS

An ammeter has an internal resistance of 50 Ω. The meter movement itself can handle up to 1 mA. If 10 mA is applied to the meter, the shunt resistor, RSH1, is approximately
A. 55 Ω
B. 5.5 Ω
C. 50 Ω
D. 9 Ω
ANS : B
The total resistance of a parallel circuit is 50 Ω. If the total current is 120 mA, the current through the 270 Ω that makes up part of the parallel circuit is approximately
A. 22 mA
B. 120 mA
C. 220 mA
D. 50 mA
ANS : A
The currents into a junction flow along two paths. One current is 4 A and the other is 3 A. The total current out of the junction is
A. 1 A
B. 7 A
C. unknown
D. the larger of the two
ANS : B
When an additional resistor is connected across an existing parallel circuit, the total resistance
A. remains the same
B. decreases by the value of the added resistor
C. increases by the value of the added resistor
D. decreases
ANS : D
When a 1.6 kΩ resistor and a 120Ω resistor are connected in parallel, the total resistance is
A. greater than 1.6 kΩ
B. greater than 120 but less than 1.6 kΩ
C. less than 120 but greater than 100 Ω
D. less than 100 Ω
ANS : C
If there are a total of 120 mA into a parallel circuit consisting of three branches, and two of the branch currents are 40 mA and 10 mA, the third branch current is
A. 50 mA
B. 70 mA
C. 120 mA
D. 40 mA
ANS : B
Three lights are connected in parallel across a 120 volt source. If one light burns out,
A. the remaining two will glow dimmer
B. the remaining two will glow brighter
C. the remaining two will not light
D. the remaining two will glow with the same brightness as before
ANS : D
Four equal-value resistors are connected in parallel. Ten volts are applied across the parallel circuit and 2 mA are measured from the source. The value of each resistor is
A. 12.5 Ω
B. 200 Ω
C. 20 KΩ
D. 50 Ω
ANS : C
A set of Christmas tree lights is connected in parallel across a 110 V source. The filament of each light bulb is 1.8 k. The current through each bulb is approximately
A. 610 mA
B. 18 mA
C. 110 mA
D. 61 mA
ANS : D
The power dissipation in each of four parallel branches is 1.2 W. The total power dissipation is
A. 1.2 W
B. 4.8 W
C. 0.3 W
D. 12 W
ANS : B
A 470 Ω resistor, a 220 Ω resistor, and a 100 Ω resistor are all in parallel. The total resistance is approximately
A. 790 Ω
B. 470 Ω
C. 60 Ω
D. 30 Ω
ANS : C
Five light bulbs are connected in parallel across 110 V. Each bulb is rated at 200 W. The current through each bulb is approximately
A. 2.2 A
B. 137 mA
C. 1.8 A
D. 9.09 A
ANS : C
Four resistors of equal value are connected in parallel. If the total voltage is 15 V and the total resistance is 600 Ω, the current through each parallel resistor is
A. 25 mA
B. 100 mA
C. 6.25 mA
D. 200 mA
ANS : C
Five 100 Ω resistors are connected in parallel. If one resistor is removed, the total resistance is
A. 25 Ω
B. 500 Ω
C. 100 Ω
D. 20 Ω
ANS : A
Four 8 Ω speakers are connected in parallel to the output of an audio amplifier. If the maximum voltage to the speakers is 12 V, the amplifier must be able to deliver to the speakers
A. 18 W
B. 1.5 W
C. 48 W
D. 72 W
ANS : D
In a certain three-branch parallel circuit, R1 has 12 mA through it, R2 has 15 mA through it, and R3 has 25 mA through it. After measuring a total of 27 mA, you can say that
A. R3 is open
B. R1 is open
C. R2 is open
D. the circuit is operating properly
ANS : A
A sudden increase in the total current into a parallel circuit may indicate
A. a drop in source voltage
B. an open resistor
C. an increase in source voltage
D. either a drop in source voltage or an open resistor
ANS : C
The following currents are measured in the same direction in a three-branch parallel circuit: 200 mA, 340 mA, and 700 mA. The value of the current into the junction of these branches is
A. 200 mA
B. 540 mA
C. 1.24 A
D. 900 mA
ANS : C
The following resistors are in parallel across a voltage source: 220Ω , 470Ω , and 560Ω . The resistor with the least current is
A. 220 Ω
B. 470 Ω
C. 560 Ω
D. impossible to determine without knowing the voltage
ANS : C
Three 47 Ω resistors are connected in parallel across a 110 volt source. The current drawn from the source is approximately
A. 2.3 A
B. 780 mA
C. 47 mA
D. 7.06 A
ANS : D
There is a total of 800 mA of current into four parallel resistors. The currents through three of the resistors are 40 mA, 70 mA, and 200 mA. The current through the fourth resistor is
A. 490 mA
B. 800 mA
C. 310 mA
D. 0 A
ANS : A
Four resistors are connected in parallel. Fifteen mA flows through resistor R. If the second resistor is 2R, the third resistor 3R, and the fourth resistor 4R, the total current in the circuit is
A. 60 mA
B. 15 mA
C. 135 mA
D. 31.25 mA
ANS : D
If one of the resistors in a parallel circuit is removed, the total resistance
A. decreases
B. increases
C. remains the same
D. doubles
ANS : B
Six resistors are in parallel. The two lowest-value resistors are both 1.2 kΩ. The total resistance
A. is less than 6 kΩ
B. is greater than 1.2 kΩ
C. is less than 1.2 kΩ
D. is less than 600 Ω
ANS : D
In a five-branch parallel circuit, there are 12 mA of current in each branch. If one of the branches opens, the current in each of the other four branches is
A. 48 mA
B. 12 mA
C. 0 A
D. 3 mA
ANS : B

EARTHING or GROUNDING Objective Questions :-

The size of the earth or ground wire is based on the
a) maximum fault current carrying through the ground wire
b) rated current carrying capacity of the service line
c) depends on the soil resistance
d) both (a) and (c)

Ans: d

Earth wire or ground wire is made of
a) copper
b) aluminium
c) iron
d) galvanized steel

Ans: d

Average resistance of human body is
a) 500 ohms
b) 1000 ohms
c) 1500 ohms
d) 2000 ohms

Ans: b

Generally grounding is provided for
a) only for the safety of the equipment
b) only for the safety of the operating personnel
c) both (a) and (b)
d) none of the above

Ans: c

Ground resistance should be designed such that
a) grounding resistance should be as low as possible
b) grounding resistance should be as high as possible
c) grounding resistance should be always zero
d) none of the above

Ans: a

For an EHV equipment for maintenance first it should be isolated and connected to ground because
a) to provide low impedance
b) to discharge the charging capacitance to ground
c) protection for operating personnel
d) both (b) and (c)

Ans: d

When earth fault occurs
a) voltage potential at the earth mat increases due to grounding
b) voltage potential at the earth mat decreases due to grounding
c) voltage potential at the earth mat remains zero irrespective of fault
d) none of the above

Ans: a

The objective of earthing or grounding is
a) to provide as low resistance possible to the ground
b) to provide as high resistance possible to the ground
c) to provide flow of positive, negative and zero sequence currents
d) none of the above

Ans: a

Moisture content in the soil __ the earth soil resistance
a) increase
b) decrease
c) does not affect
d) none of the above

Ans: b

Factors on which soil resistance depends
a) depth of the electrode
b) moisture
c) Nacl
d) all the above

Ans: d

When the 3-phase system is not grounded and if Single Line to Ground fault occurs, the voltage of the other two healthy phases will
a) Increases
b) Decreases
c) Remains unaffected

Ans: a

ELECTROSTATIC

The force between two charges is 120 N. If the distance between the charges is doubled, the force will be
(a) 60 N
(b) 30 N
(c) 40 N
(d) 15 N
Ans: b
The electric field intensity at a point situated 4 meters from a point charge is 200 N/C. If the distance is reduced to 2 meters, the field intensity will be
(a) 400 N/C
(b) 600 N/C
(c) 800 N/C
(d) 1200 N/C
Ans: c
The lines of force due to charged particles are
(a) always straight
(b) always curved
(c) sometimes curved
(d) none of the above
Ans: b
The electric field at a point situated at a distance d from straight charged conductor is
(a) proportional to d
(b) inversely proportional to d
(c) inversely proportional to d
(d) none of the above
Ans: b
The direction of electric field due +0 positive charge is .
(a) away from the charge
(b) towards the charge
(c) both (a) and (6)
(d) none of the above
Ans: a
A field line and an equipotential surface are
(a) always parallel
(b) always at 90°
(c) inclined at any angle 0
(d) none of the above
Ans: b
The ability of charged bodies to exert force on 6ne another is attributed to the existence of
(a) electrons
(b) protons
(c) neutrons
(d) electric field
Ans: d
If the sheet of a bakelite is inserted between the plates of an air capacitor, the capacitance will
(a) decrease
(b) increase
(c) remains unchanged
(d) become zero
Ans: b
A capacitor stores 0.24 coulombs at 10 volts. Its capacitance is
(a) 0.024 F
(b) 0.12 F
(c) 0.6 F
(d) 0.8 F
Ans: a
For making a capacitor, it is better to select a dielectric having
(a) low permittivity
(b) high permittivity
(c) permittivity same as that of air
(d) permittivity slightly more than that of air
Ans: b
The units of capacitance are
(a) volts/coulomb
(b) coulombs/volt
(c) ohms
(d) henry/Wb
Ans: b
If three 15 uF capacitors are connected in series, the net capacitance is
(a) 5 uF
(6) 30 uF
(c) 45 uF
(d) 50 uF
Ans: a
If three 10 uF capacitors are connected in parallel, the net cararitance is
(a) 20 uF
(b) 30 uE
(c) 40 uF
(d) 50 uF
Ans: b
A dielectric material must be
(a) resistor
(b) insulator
(c) good conductor
(d) semi conductor
Ans: b
An electrolytic capacitor can be used for
(a) D.C. only
(b) AC. only
(c) both D.C. as well as A.C.
Ans: a
The capacitance of a capacitor is not affected by
(a) distance between plates
(6) area of plates
(c) thickness of plates
(d) all of the above
Ans: c
Which of the following is not a vector ?
(a) Linear momentum
(b) Angular momentum
(c) Electric field
(d) Electric potential
Ans: b
Two plates of a parallel plate capacitor after being charged from a constant voltage source are separated apart by means of insulated handles, then the
(a) Voltage across the plates increases
(b) voltage across the plates decreases
(c) charge on the capacitor decreases
(d) charge on the capacitor increases
Ans: b
If A.C. voltage is applied to capacitive circuit, the alternating current can flow in the circuit because
(a) varying voltage produces the charging and dicharging currents
(b) of high peak value
(c) charging current can flow
(d) discharge current can flow
Ans: a
Voltage applied across a ceramic dielectric produces an electrolytic field 100 times greater than air. What will be the value of dielectric constant ?
(a) 50
(6) 100
(c) 150
(d) 200
Ans: b
Which of the following statements is correct ?
(a) Air capacitors have a black band to indicate the outside foil
(6) Electrolytic capacitor must be connected in the correct polarity
(c) Ceramic capacitors must be connected in the correct polarity
(d) Mica capacitors are available in capacitance value of 1 to 10 pF
Ans: b
The dissipation factor of a good dielectric is of the order of
(a) 0.0002
(b) 0.002
(c) 0.02
(d) 0.2
Ans: a
“The total electric flux through any closed surface surrounding charges is equal to the amount oflcharge enclosed”.
The above statement is associated with
(a) Coulomb’s square law
(b) Gauss’s law
(c) Maxwell’s first law
(d) Maxwell’s second law
Ans: b
Three capacitors each of the capacity C are given. The resultant capacity 2/3 C
can be obtained by using them
(a) all in series
(b) all in parallel
(c) two in parallel and third in series with this combination
(d) two in series and third in parallel across this combination
Ans: c
For which of the following parameter variation, the capacitance of the capacitor remains unaffected ?
(a) Distance between plates
(b) Area of the plates
(c) Nature of dielectric
(d) Thickness of the plates
Ans: d
Which of the following statement is true ?
(a) The current in the discharging capacitor grows linearly
(b) The current in the dicharging capacitor grows exponentially
(c) The current in the discharging capacitor decays exponentially
(d) The current in the discharging capacitor decreases constantly
Ans: b
Which of the following expression is correct for electric field strength ?
(a) E = D/E
(b) E = D2/t
(c) E = jtD
(d) E= nD2
Ans: a
In a capacitor the electric charge is stored in
(a) metal plates
(b) dielectric
(c) both (a) and (6)
(d) none of the above
Ans: b
Which of the following materials has the highest value of dielectric constant?
(a) Glass
(b) Vacuum
(c) Ceramics
(d) Oil
Ans: c
Which of the following capacitors will have the least variation ?
(a) Paper capacitor
(b) Ceramic capacitor
(c) Silver plated mica capacitor
(d) None of the above
Ans: c
Which of the following statements is incorrect ?
(a) The leakage resistance of ceramic capacitors is generally high
(b) The stored energy in a capacitor decreases with reduction in value of capacitance
(c) The stored energy in a capacitor increases with applied voltage
(d) A wire cable has distributed capacitance between the conductors
Ans: b
Which of the following capacitors has relatively shorter shelf life ?
(a) Mica capacitor
(b) Electrolytic capacitor
(c) Ceramic capacitor
(d) Paper capacitor
Ans: b
The sparking between two electrical contacts can be reduced by inserting a
(a) capacitor in parallel with contacts
(6) capacitor in series with each contact
(c) resistance in line
(d) none of the above
Ans: a
In the case of a lossy capacitor, its series equivalent resistance value will be
(a) small
(b) very small
(c) large
(d) zero
Ans: c
The power dissipated in a pure capacitor is
(a) zero
(6) proportional to applied voltage
(c) proportional to value of capacitance
(d) both (b) and (c) above
Ans: a
In a capacitive circuit
(a) a steady value of applied voltage causes discharge
(b) an increase in applied voltage makes a capacitor charge
(c) decrease in applied voltage makes a capacitor charge
(d) none of the above
Ans: b
When a dielectric slab is introduced in a parallel plate capacitor, the potential difference between plates will
(a) remain uncharged
(b) decrease
(c) increase
(d) become zero
Ans: b
Capacitance increases with
(a) increase in plate area and decrease in distance between the plates
(b) increase in plate area and distance between the plates
(c) decrease in plate area and value of applied voltage
(d) reduction in plate area and distance between the plates
Ans: a
A capacitor consists of
(a) two insulators separated by a conductor
(b) two conductors separated by an insulator
(c) two insulators only
(d) two conductors only
Ans: b
A gang condenser is a
(a) polarised capacitor
(6) variable capacitor
(c) ceramic capacitor
(d) none of the above
Ans:
A paper capacitor is usually available in the form of
(a) tubes
(b) rolled foil
(c) disc
(d) meshed plates
Ans: b
Air capacitors are generally available in the range
(a) 10 to 400 pF
(b) 1 to 20 pF
(c) 100 to 900 pF
(d) 20 to 100 pF
Ans: a
The unit of capacitance is
(a) henry
(b) ohm
(c) farad
(d) farad/m
Ans: c
A capacitor charged to 200 V has 2000 (iC of charge. The value of capacitance will be
(a) 10 F
(6) 10 uF
(c) 100 nF
(d) 1000 uF
Ans: b
A capacitor in a circuit became hot and ultimately exploded due to wrong connections, which type of capacitor it could be ?
(a) Paper capacitor
(b) Ceramic capacitor
(c) Electrolytic capacitor
(d) Any-of the above
Ans: c
Energy stored in the electric field of a capacitor C when charged from a D.C source of voltage V is equal to joules
(a) CV2
(b) C2V
(c) CV2
(d) CV
Ans: a
The absolute permittivity of free space is given by
(a) 8.854 x 1(T9 F/m)
(6) 8.854 x 1(T10 F/m)
(c) 8.854 x KT11 F/m
(d) 8.854 x 10″12 F/m
Ans: b
The relative permittivity of free space is given by
(a) 1
(b) 10
(c) 100
(d) 1000
Ans: a
Electric field intensity is a quantity
(a) scalar
(b) vector
(c) both (a) and (6)
(d) none of the above
Ans: b
When 4 volts e.m.f. is applied across a 1 farad capacitor, it will store energy of
(a) 2 joules
(b) 4 joules
(c) 6 joules
(d) 8 joules
Ans: d
The capacitor preferred for high frequency circuits is
(a) air capacitor
(b) mica capacitor
(c) electrolytic capacitor
(d) none of the above
Ans: b
The capacity of capacitor bank used in power factor correction is expressed in terms of
(a) kW
(b) kVA
(c) kVAR
(d) volts
Ans: c
While testing a capacitor with ohm meter, if the capacitor shows charging, but the final resistance reading is appreciably less than normal, it can be concluded that the capacitor is
(a) short-circuited
(b) open circuited
(c) alright
(d) leaky
Ans: d
If a 6 uF capacitor is charged to 200 V, the charge in coulombs will be
(a) 800 uC
(b) 900 uC
(c) 1200 uC
(d) 1600 uC
Ans: c
Which capacitor will be physically smaller for the same ratings ?
(a) Ceramic capacitor
(b) Paper capacitor
(c) Both will be of equal size
(d) None of the above
Ans: a
What is the value of capacitance that must be connected in parallel with 50 pF condenser to make an equivalent capacitance of 150 pF ?
(a) 50 pF
(b) 100 pF
(c) 150 pF
(d) 200 pF
Ans: b
A mica capacitor and a ceramic capacitor both have the same physical dimensions. Which will have more value of capacitance ?
(a) Ceramic capacitor
(b) Mica capacitor
(c) Both will have identical value of capacitance
(d) It depends on applied voltage
Ans: a
Which of the following material has least value of dielectric constant ?
(a) Ceramics
(b) Oil
(c) Glass
(d) Paper
Ans: b
Which of the following capacitors will have the least value of breakdown voltage ?
(a) Mica
(b) Paper
(c) Ceramic
(d) Electrolytic
Ans: d
The breakdown voltage for paper capacitors is usually
(a) 20 to 60 volts
(b) 200 to 1600 volts
(c) 2000 to 3000 volts
(d) more than 10000 volts
Ans:
Dielectric constant for mica is nearly
(a) 200
(b) 100
(c) 3 to 8
(d) 1 to 2
Ans: c
The value of dielectric constant for vacuum is taken as
(a) zero
(b) 1
(c) 4
(d) 10
Ans: b
Which of the following capacitors is marked for polarity ?
(a) Air
(b) Paper
(c) Mica
(d) Electrolytic
Ans: d
Which of the following capacitors can be used for temperature compensation ?
(a) Air capacitor
(b) Ceramic capacitor
(c) Paper capacitor
(d) None of the above
Ans: b
Which of the following statements is incorrect ?
(a) The thinner the dielectric, the more the capacitance and the lower the voltage breakdown rating for a capacitor .
(b) A six dot mica capacitor colour coded white, green, black, red and yellow has the capacitance value of 500 pF
(c) Capacitors in series provide less capacitance but a higher voltage breakdown rating for the combination
(d) A capacitor can store charge because it has a dielectric between two conductors
Ans: b
Paper capacitors usually have a tolerance of
(a) ± 5%
(b) ± 10%
(c) ± 15%
(d) ± 20%
Ans: b
For closer tolerances which of the following capacitors is usually preferred ?
(a) Paper capacitor
(b) Mica capacitor
(c) Ceramic disc capacitor
(d) None of the above
Ans: b
The electrostatic force between two charges of one coulomb each and placed at a distance of 0.5 m will be
(a) 36 x 10fa
(b) 36 x 107 N
(c) 36 x 108 N
(d) 36 x 109 N
Ans: d
The units of volume charge density are
(a) Coulomb/meter
(b) Coulomb/meter
(c) Coulomb/meter
(d) Coulomb/meter
Ans: c
“The surface integral of the normal component of the electric displacement D over any closed surface equals the charge enclosed by the surface”.
The above statement is associated with
(a) Gauss’s law
(b) Kirchhoff s law
(c) Faraday’s law
(d) Lenz’s law
Ans: a
Dielectric strength of mica is
(a) 10 to 20 kV/mm
(6) 30 to 50 kV/mm
(c) 50 to 200 kV/mm
(d) 300 to 500 kV/mm
Ans: c
The dielectric constant (relative permittivity) of glass is given by
(a) 0.1 to 0.4
(b) 0.5 to 1.0
(c) 2.0 to 4.0
(d) 5 to 100
Ans: d
capacitors are mainly used for radio frequency tuning.
(a) Paper
(b) Air
(c) Mica
(d) Electrolytic
Ans: b
capacitors can be used only for D.C.
(a) Air
(b) Paper
(e) Mica
(d) Electrolytic
Ans: d
capacitors are used in transistor circuits.
(a) Ceramic
(b) Paper
(c) Air
(d) Electrolytic
Ans: a
capacitors are used for audio frequency and radio frequency coupling and tuning.
(a) Air
(b) Mica
(c) Plastic film
(d) Ceramic
Ans: b
The inverse of capacitance is called
(a) reluctance
(b) conductance
(c) susceptance
(d) elastance
Ans: d
When the dielectric is homogeneous,the potential gradient is
(a) uniform
(b) non-uniform
(c) zero
(d) any of the above
Ans: a
The potential gradient across the material of low permittivity is than across the material of high permittivity.
(a) smaller
(b) greater
(c) both (a) and (b)
(d) none of the above
Ans: b
________field is associated with the capacitor.
(a) Electric
(b) Magnetic
(c) Both (a) and (b)
(d) None of the above
Ans: a
A capacitor having capacitance of 5 uF is charged to a potential difference of 10,000 V. The energy stored in the capacitor is
(a) 50 joules
(b) 150 joules
(c) 200 joules
(d) 250 joules
Ans: d
A single core cable used on 33000 V has conductor diameter 10 mm and the internal diameter of sheath 25 mm. The maximum electrostatic stress in the cable is
(a) 62 x 105 V/m
(b) 72 x 105 V/m
(c) 82 x 105 V/m
(d) 92 x 105 V/m
Ans: b
Two infinite parallel plates 10 mm apart have maintained between them a potential difference of 100 V. The acceleration of an electron placed between them is
(a) 0.56 x 1015 m/s2
(b) 1.5 x 1015 m/s2
(c) 1.6 x 1015 m/s2
(d) 1.76 x 1015 m/s2
Ans: d
The total deficiency or excess of electrons in a body is known as
(a) current
(b) voltage
(c) potential gradient
(d) charge
Ans: d
The relative permittivity has the following units
(a) F/m
(b) m/F
(c) Wb/m
(d) no units
Ans: c
The phenomenon of an uncharged body getting charged merely by the nearness of a charged body is known as
(a) pholoelectric effect
(b) chemical effect
(c) magnetic effect
(d) induction
Ans: d
A unit tube of flux is known as tube
(a) Newton
(b) Faraday
(c) Michale
(d) None of the above
Ans: b
The number of Faraday tubes of flux passing through a surface in an electric field is called
(a) electric flux
(6) electric flux density
(c) magnetic flux density
(d) electric charge density
Ans: a
The unit of electric instensity is
(a) N/C2
(b) Wb/m2
(c) N/C
(d) N2/C
Ans:
The value of E within the field due to a point charge can be found with the help of
(a) Faraday’s laws
(b) Kirchhoff s laws
(c) Coulomb’s laws
(d) none of the above
Ans: c
at a point may be defined as equal to the lines of force passing normally through a unit cross section at that point.
(a) Electric intensity
(6) Magnetic flux density
(c) Electric flux
(d) None of the above
Ans: a
Electric intensity at any point in an electric field is equal to the at that point.
(a) electric flux
(b) magnetic flux density
(c) potential gradient
(d) none of the above
Ans: c
Electric displacement is a______quantity.
(a) scalar
(b) vector
(c) both of the above
(d) none of the above
Ans: b
at a point is equal to the negative potential gradient at that point.
(a) Electric intensity
(6) Electric flux
(c) Magnetic flux
(d) Magnetic flux density
Ans: a
The unit of dielectric strength is given by
(a) V/m
(b) V2/m
(c) m/V
(d) m/V2
Ans: a
Dielectric strength ______ with increasing thickness
(a) increases
(b) decreases
(c) remains unaltered
(d) none of the above
Ans: b
The property of a capacitor to store electricity is called its
(a) capacitance
(b) charge
(c) energy
(d) none of the above
Ans: a
is that property of a capacitor which delays any change of voltage across it.
(a) Inductance
(b) Capacitance
(c) Potential gradient
(d) None of the above
Ans: b
A capacitance of 100 fiF is connected in series with a resistance of 8000 £2. The time constant of the circuit is
(a) 0.2 s
(b) 0.4 s
(c) 0.6 s
(d) 0.8 s
Ans: d
In a cable capacitor, voltage gradient is maximum at the surface of the
(a) earth
(b) conduction
(c) sheath
(d) insulator
Ans: b
The time constant of an R-C circuit is defined as the time during which capacitor charging voltage actually rises to ______ percent of its value.
(a) 37, initial
(b) 62, initial
(c) 62, final
(d) 37, final
Ans: c

102 The time constant and R-C circuit may also be defined as the time during which the charging current falls to ______ percent of its initial maximum value,
(a) 37
(b) 42
(c) 63
(d) 73
Ans: a

The capacitance of a capacitor is influenced by
(a) plate area
(b) plate separation
(c) nature of dielectric
(d) none of the above
(e) all of the above
Ans:
A capacitor consists of two
(a) ceramic plates and one mica disc
(b) insulators separated by a dielectric
(c) silver-coated insulators
(d) conductors separated by an insulator
Ans: d
Permittivity is expressed in
(a) Farad/sq-m
(b) Farad/meter
(c) Weber/meter
(d) Weber/sq-m
Ans: b
Dielectric strength of a material depends on
(a) moisture content
(b) temperature
(c) thickness
(d) all of the above
(e) none of the above
Ans: d
What will happen to an insulating medium if voltage more than the breakdown voltage is applied on it ?
(a) It will become magnetic
(b) It will melt
(c) It will get punctured or cracked
(d) Its molecular structure will get changed
Ans: c
Which medium has the least dielectric strength ?
(a) Paraffin wax
(b) Quartz
(c) Glass
(d) Air
Ans: d
1 volt/meter is same as
(a) 1 meter/coulomb
(6) 1 newton meter
(c) 1 newton/meter
(d) 1 joule/coulomb
Ans: c
One volt is the same as
(a) one joule/coulomb
(b) one coulomb/joule
(c) one coulomb
(d) one joule
Ans: a
The capacitance between two plates increases with
(a) shorter plate area and higher applied voltage
(6) shorter plate area and shorter distance between them
(c) larger plate area, longer distance between plates and higher,applied voltage
(d) larger plate area and shorter distance between plates
Ans: d
The capacitance C is charged through a resistance R. The time constant of the charging circuit is given by
(a) CIR
(b) 1/RC
(c) RC
(d) RIC
Ans: c
The bridge used for the measurement of the value of the capacitance is
(a) Wien’s bridge
(b) Wheatstone bridge
(c) Schering bridge
(d) Hay’s bridge
Ans: c
If an ohmmeter reading immediately goes practically to zero and stays there, capacitor is
(a) charged
(b) short-circuited
(c) lossy
(d) satisfactory
Ans: b
Out of the following capacitors of identical rating which one will have the smallest dimensions ?
(a) Aluminium foil capacitor
(b) Mica capacitor
(c) Ceramic capacitor
(d) Paper capacitor
Ans: c
An uncharged conductor is placed near a charged conductor, then
(a) the uncharged conductor gets charged by conduction
(6) the uncharged conductor gets charged by induction and then attracted towards the charging body
(c) the uncharged conductor is attracted first and then charged by induction
(d) it remains as such
Ans: b
The presence of an uncharged conductor near a charged one increases the
(a) charge of the charged conductor
(6) capacity of the charged conductor
(c) potential of the charged conductor
(d) all of the above
Ans: b
Paper condenser is
(a) always polarised
(6) usually of fixed value
(c) electrolytic condenser
(d) a variable condenser
Ans: b
Mica capacitors are characterised by all of the following except
(a) stable operation
(b) accurate value
(c) low leakage reactance
(d) low losses
Ans: c
A potential of 400 V is applied to a capacitor, the plates of which are 4 mm apart. The strength of electric field is
(a) 100 kV/m
(b) 10 kV/m
(c) 5 kV/m
(d) 2 kV/m
Ans: a
For a good 0.05 uF capacitor ohmmeter reading should
(a) show low resistance momentarily and back off to a very high resistance
(6) show high resistance momentarily and then a very low resistance
(c) go quickly to 50 ohm approximately and remain there
(d) not move at all
Ans: a
The ohmmeter reading for a short circuited capacitor is
(a) infinity
(b) few kilo ohms
(c)few megohms
(d) zero
Ans: d
Which of the following statements is correct ?
(a) Mica capacitors are available in capacitance values of 5 to 20 uF
(b) Air capapitors have a black band to indicate the outside foil
(c) Electrolytic capacitors must be connected in correct polarity
(d) Ceramic capacitors must be connected in correct polarity
Ans: c
Which of the following capacitors preferred for high frequency circuits ?
(a) Air capacitor
(6) Electrolytic capacitor
(c) Mica capacitor
(d) none of the above
Ans: c
An electrolytic capacitor is generally made to provide
(a) low capacitance
(b) fixed capacitance
(c) variable capacitance
(d) large value of capacitance
Ans: d
In order to remove static electricity from machinery
(a) construct insulated cabins
(b) insulate the machinery
(c) ground the framework
(d) humidify the surroundings
Ans: c
If a third equal and similar charge is placed between two equal and similar charges, then this third charge will
(a) move out of the field of influence of the two charges
(b) remain in stable equilibrium
(c) not be in equilibrium
(d) be in unstable equilibrium
Ans: b
A region around a stationary electric charge has
(a) an electric field
(b) a magnetic field
(c) both (a) and (6)
(d) none of the above
Ans: a
The minimum value of potential gradient in a cable occurs in
(a) insulation
(b) conductor
(c) outer sheath
(d) uniformly all over
Ans: a
Dielectric strength of medium
(a) increases with rise in temperature
(b) increases with moisture content
(c) is same for all insulating materials
(d) none of the above
Ans: d
Acharge which when placed in vacuum from an equal and similar charge repels with a force of 9 x 10 N, is known as
(a) milli-coulomb
(b) micro-coulomb
(c) pico-coulomb
(d) coulomb
Ans: b
Dielectric strength of a medium is usually expressed in
(a) J/mm
(b) C/m2
(c) kV/mm
(d) N/mm
Ans: c
A positive and a negative charge are initially 50 mm apart. When they are moved close together so that they are now only 10 mm apart, the force between them will be
(a) 5 times smaller than before
(b) 5 times greater than before
(c) 10 times greater than before
(d) 25 times larger than before
Ans: d
Which is the most superior dielectric out of the following ?
(a) Air
(b) Glass
(c) Bakelite
(d) Paper
Ans: c
When a dielectric is placed in an electric field the field strength
(a) decreases
(b) increases
(c) reduces to zero
(d) remain unchanged
Ans: a
To prevent the generation of static charges on rubber or flat leather
(a) surface is moistened
(b) conductive dressing is done
(c) oil compound dressing is done
(d) talcum powder is sprayed on the surface
Ans: b
Which of the following capacitor is preferred in case of single phase motor ?
(a) Mica capacitor
(b) Paper capacitor
(c) Electrolytic capacitor
(d) Ceramic capacitor
Ans: c
A capacitance is a circuit component that opposes the change in circuit
(a) current
(b) voltage
(c) impedance
(d) none of the above
Ans: a
A condenser suitable for D.C. only is
(a) metallic plate variable gang condenser
(b) metallic paper capacitor
(c) oil impregrated paper condenser
(d) poled aluminium electrolytic condenser
Ans: d
In a capacitor, the electric charge is stored in
(a) metal plates
(b) dielectric
(c) dielectric as well as metal plates
(d) none of the above
Ans: b

MAGNETISM and ELECTROMAGNETISM

Tesla is a unit of
(a) field strength
(b) inductance
(c) flux density
(d) flux
Ans: c
A permeable substance is one
(a) which is a good conductor
(6) which is a bad conductor
(c) which is a strong magnet
(d) through which the magnetic lines of force can pass very easily
Ans: d
The materials having low retentivity are suitable for making
(a) weak magnets
(b) temporary magnets
(c) permanent magnets
(d) none of the above
Ans: b
A magnetic field exists around
(a) iron
(b) copper
(c) aluminium
(d) moving charges
Ans: d
Ferrites are materials.
(a) paramagnetic
(b) diamagnetic
(c) ferromagnetic
(d) none of the above
Ans: c
Air gap has_______eluctance as compared to iron or steel path
(a) little
(b) lower
(c) higher
(d) zero
Ans: b
The direction of magnetic lines of force is
(a) from south pole to north pole
(b) from north pole to south pole
(c) from one end of the magnet to another
(d) none of the above
Ans: b
Which of the following is a vector quantity ?
(a) Relative permeability
(b) Magnetic field intensity
(c) Flux density
(d) Magnetic potential
Ans: b
The two conductors of a transmission line carry equal current I in opposite directions. The force on each conductor is
(a) proportional to 7
(b) proportional to X
(c) proportional to distance between the conductors
(d) inversely proportional to I
Ans: b
A material which is slightly repelled by a magnetic field is known as
(a) ferromagnetic material
(b) diamagnetic material
(c) paramagnetic material
(d) conducting material
Ans: b
When an iron piece is placed in a magnetic field
(a) the magnetic lines of force will bend away from their usual paths in order to go away from the piece
(b) the magnetic lines of force will bend away from their usual paths in order to pass through the piece
(c) the magnetic field will not be affected
(d) the iron piece will break
Ans: b
Fleming’s left hand rule is used to find
(a) direction of magnetic field due to current carrying conductor
(b) direction of flux in a solenoid
(c) direction of force on a current carrying conductor in a magnetic field
(d) polarity of a magnetic pole
Ans: c
The ratio of intensity of magnetisation to the magnetisation force is known as
(a) flux density
(b) susceptibility
(c) relative permeability
(d) none of the above
Ans: b
Magnetising steel is normals difficult because
(a) it corrodes easily
(6) it has high permeability
(c) it has high specific gravity
(d) it has low permeability
Ans: d
The left hand rule correlates to
(a) current, induced e.m.f. and direction of force on a conductor
(b) magnetic field, electric field and direction of force on a conductor
(c) self induction, mutual induction and direction of force on a conductor
(d) current, magnetic field and direction of force on a conductor
Ans: d
The unit of relative permeability is
(a) henry/metre
(b) henry
(c) henry/sq. m
(d) it is dimensionless
Ans: d
A conductor of length L has current I passing through it, when it is placed parallel to a magnetic field. The force experienced by the conductor will be
(a) zero
(b) BLI
(c) B2LI
(d) BLI2
Ans: a
The force between two long parallel conductors is inversely proportional to
(a) radius of conductors
(b) current in one conductor
(c) product of current in two conductors
(d) distance between the conductors
Ans: d
Materials subjected to rapid reversal of magnetism should have
(a) large area oiB-H loop
(b) high permeability and low hysteresis loss
(c) high co-ercivity and high retentivity
(d) high co-ercivity and low density
Ans: b
Indicate which of the following material does not retain magnetism permanently.
(a) Soft iron
(b) Stainless steel
(e) Hardened steel
(d) None of the above
Ans: a
The main constituent of permalloy is
(a) cobalt
(b) chromium
(c) nickel
(d) tungsten
Ans: c
The use of permanent magnets is. not made in
(a) magnetoes
(6) energy meters
(c) transformers
(d) loud-speakers
Ans: c
Paramagnetic materials have relative permeability
(a) slightly less than unity
(b) equal to unity
(c) slightly more than unity
(d) equal to that ferromagnetic mate rials
Ans: c
Degaussing is the process of
(a) removal of magnetic impurities
(b) removing gases from the materials
(c) remagnetising metallic parts
(d) demagnetising metallic parts
Ans:
Substances which have permeability less than the permeability of free space are known as
(a) ferromagnetic
(b) paramagnetic
(c) diamagnetic
(d) bipolar
Ans: c
Two infinitely long parallel conductors in vacuum any separated 1 metre between centers >then a current of 1 ampere flows the. uk each conductor, produce on each other a force of
(a) 2 x 1(T2 N/m)
(b) 2 x KT3 N/m
(c) 2 x 10″5 N/m
(d) 2x 1(T7 N/m)
Ans: d
In the left hand rule, forefinger always represents
(a) voltage
(b) current
(c) magnetic field
(d) direction of force on the conductor
Ans: c
Which of the following is a ferromagnetic material ?
(a) Tungsten
(b) Aluminium
(c) Copper
(d) Nickel
Ans: d
Ferrites are a sub-group of
(a) non-magnetic materials
(6) ferro-magnetic materials
(c) paramagnetic materials
(d) ferri-magnetic materials
Ans: d
Gilbert is a unit of
(a) electromotive force
(6) magnetomotive force
(c) conductance
(d) permittivity
Ans: b
The working of a meter is based on the use of a permanent magnet. In order to protect the meter functioning from stray magnetic fields
(a) meter is surrounded by strong magnetic fields
(b) a soft iron shielding is used
(c) a plastic shielding is provided
(d) a shielding of anon-magnetic material is used
Ans: b
Reciprocal of permeability is
(a) reluctivity
(b) susceptibility
(c) permittivity
(d) conductance
Ans: a
The relative permeability is less than unity is case of
(a) ferromagnetic materials
(b) ferrites
(c) non-ferrous materials
(d) diamagnetic materials
Ans: d
Which of the following is the unit of magnetic flux density ?
(a) weber
(b) lumens
(c) tesla
(d) none of the above
Ans: c
The magnetism left in the iron after exciting field has been removed is known as
(a) permeance
(b) residual magnetism
(c) susceptance
(d) reluctance
Ans: b
Which of the following is not a unit of flux?
(a) Maxwell
(b) Telsa
(c) Weber
(d) All of the above
Ans: b
Which of the following is expected to have the maximum permeability ?
(a) Brass
(b) Copper
(c) Zinc
(d) Ebonite
Ans: d
One telsa is equal to
(a) 1 Wb/mm2
(b) 1 Wb/m
(c) 1 Wb/m2
(d) 1 mWb/m2
Ans: c
Out of the following statements, concerning an electric field, which statement is not true ?
(a) The electric intensity is a vector quantity
(b) The electric field intensity at a point is numerically equal to the force exerted upon a charge placed at that point
(c) An electric field is defined as a point in space at which an electric charge would experience a force
(d) Unit field intensity in the exertion of a force of one newton on a charge of one coulomb
Ans: b
When a magnet is in motion relative to a coil the induced e.m.f. does not depend upon
(a) resistance of the coil
(b) motion of the magnet
(c) number of turns of the coil
(d) pole strength of the magnet
Ans: a
One maxwell is equal to
(a) 10 webers
(b) 10 webers
(c) 10 webers
(d) 10 webers
Ans: d
When two ends of a circular uniform wire are joined to the terminals of a battery, the field at the center of the circle
(a) will be zero
(b) will be infinite
(c) will depend on the amount of e.m.f. applied
(d) will depend on the radius of the circle
Ans: d
Susceptibility is positive for
(a) non-magnetic substances
(b) diamagnetic substances
(c) ferromagnetic substances
(d) none of the above
Ans: c
Two long parallel conductors carry 100 A. If the conductors are separated by 20 mm, the force per meter of length of each conductor will be
(a) 100 N
(b) 10 N
(c) 1 N
(d) 0.1 N
Ans: d
A 300 mm long conductor is carrying a current of 10 A and is situated at right angles to a magnetic field having a flux density of 0.8 T ; the force on the conductor will be
(a) 240 N
(6) 24 N
(c) 2.4 N
(d) 0.24 N
Ans: c
A 200 turn coil having an axial length of 30 mm and a radius of 10 mm is pivoted in a magnetic field having a flux density of 0.8 T. If the coil carries a current of 0.5 A, the torque acting on the coil will be
(a) 8 N-m
(b) 0.48 N-m
(e) 0.048 N-m
(d) 0.0048 N-m
[Hint. Torque = 2BIlNr N-m]
Ans: c
The electromagnet has 50 turns and a current of 1A flows through the coil. If the length of the magnet circuit is 200 mm, what is the magnetic field strength ?
(a) 2500 AT/m
(b) 250 AT/m
(c) 25 AT/m
(d) 2.5 AT/m
Ans: b
What is the magnitude and the direction of force per 1.1m length of a pair of conductors of a direct current linecarrying 10 amperes and spaced 100 mm apart ?
(a) 22 x 10″8 N
(b) 22 x 10″7 N
(c) 22 x 10-6 N
(d) 22 x 10″5 N
Ans: d
A square cross-sectional magnet has a pole strength of 1 x 10 Wb and cross sectional area of 20 mm x 20 mm. What is the strength at a distance of 100 mm from the unit pole in air ?
(a) 63.38 N/Wb
(b) 633.8 N/Wb
(c) 6338 N/Wb
(d) 63380 N/Wb
Ans: c
The unit of flux is the same as that of
(a) reluctance
(b) resistance
(c) permeance
(d) pole strength
Ans: d
Unit for quantity of electricity is
(a) ampere-hour
(b) watt
(c) joule
(d) coulomb
Ans: d
The Biot-savart’s law is a general modification of
(a) Kirchhoffs law
(b) Lenz’s law
(c) Ampere’s law
(d) Faraday’s laws
Ans: c
The most effective and quickest may of making a magnet from soft iron is by
(a) placing it inside a coil carrying current
(b) induction
(c) the use of permanent magnet
(d) rubbing with another magnet
Ans: a
The commonly used material for shielding or screening magnetism is
(a) copper
(b) aluminium
(c) soft iron
(d) brass
Ans: c
If a copper disc is rotated rapidly below a freely suspended magnetic needle, the magnetic needle shall start rotating with a velocity
(a) less than that of disc but in opposite direction
(b) equal to that of disc and in the same direction
(c) equal to that of disc and in the opposite direction
(d) less than that of disc and in the same direction
Ans: d
A permanent magnet
(a) attracts some substances and repels others
(b) attracts all paramagnetic substances and repels others
(c) attracts only ferromagnetic substances
(d) attracts ferromagnetic substances and repels all others
Ans: a
The retentivity (a property) of material is useful for the construction of
(a) permanent magnets
(b) transformers
(c) non-magnetic substances
(d) electromagnets
Ans: a
The relative permeability of materials is not constant.
(a) diamagnetic
(b) paramagnetic
(c) ferromagnetic
(d) insulating
Ans: c
The materials are a bit inferior conductors of magnetic flux than air.
(a) ferromagnetic
(b) paramagnetic
(c) diamagnetic
(d) dielectric
Ans: c
Hysteresis loop in case of magnetically hard materials is more in shape as compared to magnetically soft materials.
(a) circular
(b) triangular
(c) rectangular
(d) none of the above
Ans: c
A rectangular magnet of magnetic moment M is cut into two piece of same length, the magnetic moment of each piece will be
(a) M
(6) M/2
(c) 2 M
(d) M/4
Ans: b
A keeper is used to
(a) change the direction of magnetic lines
(b) amplify flux
(c) restore lost flux
(d) provide a closed path for flux
Ans: d
Magnetic moment is a
(a) pole strength
(6) universal constant
(c) scalar quantity
(d) vector quantity
Ans: d
The change of cross-sectional area of conductor in magnetic field will affect
(a) reluctance of conductor
(b) resistance of conductor
(c) (a) and (b) both in the same way
(d) none of the above
Ans: c
The uniform magnetic field is
(a) the field of a set of parallel conductors
(b) the field of a single conductor
(c) the field in which all lines of magnetic flux are parallel and equidistant
(d) none of the above
Ans: c
The magneto-motive force is
(a) the voltage across the two ends of exciting coil
(b) the flow of an electric current
(c) the sum of all currents embraced by one line of magnetic field
(d) the passage of magnetic field through an exciting coil
Ans: c
What will be the current passing through the ring shaped air cored coil when number of turns is 800 and ampere turns are 3200 ?
(a) 2
(b) 4
(c) 6
(d) 8
Ans: b
What will be the magnetic potential difference across the air gap of 2 cm length in magnetic field of 200 AT/m ?
(a) 2 AT
(b) 4 AT
(c) 6 AT
(d) 10 AT
Ans: b
Which of the following statements is correct ?
(a) The magnetic flux inside an exciting coil is lower than its outside surface
(6) The magnetic flux inside an exciting coil is zero
(e) The magnetic flux inside the exciting coil is greater than its outside surface
(d) The magnetic flux inside the exciting coil is same as on its outside surface
Ans: d
A certain amount of current flows through a ring-shaped coil with fixed number of turns. How does the magnetic induction B varies inside the coil if an iron core is threaded into coil without dimensional change of coil ?
(a) Decreases
(b) Increases
(c) Remains same
(d) First increases and then decreases depending on the depth of iron in¬sertion
Ans: b
The magnetic reluctance of a material
(a) decreases with increasing cross sectional area of material
(6) increases with increasing cross-sec-tional area of material
(c) does not vary with increasing cross-sectional area of material
(d) any of the above
Ans: a
The initial permeability of an iron rod is
(a) the highest permeability of the iron rod
(b) the lowest permeability of the iron rod
(c) the permeability at the end of the iron rod
(d) the permeability almost in non-magnetised state
Ans: d
How does the magnetic compass needle behave in a magnetic field ?
(a) It assures a position right angle to magnetic field
(b) It starts rotating
(c) It assures a position which follows a line of magnetic flux
(d) None of the above
Ans: c
In a simple magnetic field the strength of magnet flux
(a) is constant and has same value in energy part of the magnetic field
(6) increases continuously from initial value to final value
(c) decreases continuously from initial value to final value
(d) first increases and then decreases till it becomes zero
Ans: d
The stray line of magnetic flux is defined as
(a) a line vertical to the flux lines
(b) the mean length of a ring shaped coil
(c) a line of magnetic flux in a non-uniform field
(d) a line of magnetic flux which does not follow the designed path
Ans: d
The bar magnet has
(a) the dipole moment
(b) monopole moment
(c) (a) and (b) both
(d) none of the above
Ans: a
Which of the following materials are diamagnetic ?
(a) Silver
(b) Copper
(c) Silver and copper
(d) Iron
Ans: c
Which of the following type of materials are not very important for engineering applications ?
(a) Ferromagnetic
(b) Paramagnetic
(c) Diamagnetic
(d) None of the above
Ans: c
The susceptibility of paramagnetic materials generally lies between
(a) KT3 and 1CT6
(b) 1CT3 and 1CT7
(c) KT4 and KT8
(d) 10″2 and KT5
Ans: a
For which of the following materials the saturation value is the highest ?
(a) Ferromagnetic materials
(6) Paramagnetic materials
(c) Diamagnetic materials
(d) Ferrites
Ans: d
The magnetic materials exhibit the property of magnetisation because of
(a) orbital motion of electrons
(b) spin of electrons
(c) spin of nucleus
(d) either of these
(e) all of the above
Ans: c
For which of the following materials the net magnetic moment should be zero ?
(a) Diamagnetic materials
(b) Ferrimagnetic materials
(c) Antiferromagnetic materials
(d) Antiferrimagnetic materials
Ans: c
The attraction capacity of electromagnet will increase if the
(a) core length increases i
(b) core area increases
(c) flux density decreases
(d) flux density increases
Ans: d
Which of the following statements is correct ?
(a) The conductivity of ferrites is better than ferromagnetic materials
(b) The conductivity of ferromagnetic materials is better than ferrites
(c) The conductivity of ferrites is very high
(d) The conductivity of ferrites is same as that of ferromagnetic materials
Ans: a
Temporary magnets are used in
(a) loud-speakers
(b) generators
(c) motors
(d) all of the above
Ans: d
Main causes of noisy solenoid are
(a) strong tendency of fan out of laminations at the end caused by repulsion among magnetic lines of force
(b) uneven bearing surface, caused by dirt or uneven wear between moving and stationary parts
(c) both of above
(d) none of the above
Ans: c
Strength of an electromagnet can be increased by
(a) increasing the cross-sectional area
(b) increasing the number of turns
(c) increasing current supply
(d) all above methods
Ans:
Core of an electromagnet should have
(a) low coercivity
(6) high susceptibility
(c) both of the above
(d) none of the above
Ans: c
Magnetism of a magnet can be destroyed by
(a) heating
(b) hammering
(c) by inductive action of another magnet
(d) by all above methods
Ans: d
MAGNETIC CIRCUIT
1. An air gap is usually inserted in magnetic circuits to
  (a) increase m.m.f.
  (b) increase the flux
  (c) prevent saturation
  (d) none of the above
  Ans: c
2. The relative permeability of a ferromagnetic material is
  (a) less than one
  (b) more than one
  (c) more than 10
  (d) more than 100 or 1000
  Ans: d
3. The unit of magnetic flux is
  (a) henry
  (b) weber
  (c) ampereturn/weber
  (d) ampere/metre
  Ans: b
4. Permeability in a magnetic circuit corresponds to______ in an electric circuit.
  (a) resistance
  (b) resistivity
  (c) conductivity
  (d) conductance
  Ans: c
5. Point out the wrong statement.
  Magnetic leakage is undesirable in electric machines because it
  (a) lowers their power efficiency
  (b) increases their cost of manufacture
  (c) leads to their increased weight
  (d) produces fringing
  Ans: a
6. Relative permeability of vacuum is
  (a) 1
  (b) 1 H/m
  (c) 1/4JI
  (d) 4n x 10-‘ H/m
  Ans: a
7. Permanent magnets are normally made of
  (a) alnico alloys
  (b) aluminium
  (c) cast iron
  (d) wrought iron
  Ans: a
8. Energy stored by a coil is doubled when its current is increased by percent.
  (a) 25
  (b) 50
  (c)41.4
  (d) 100
  Ans: c
9. Those magnetic materials are best suited for making armature and transformer cores which have____permeability and_______hystersis loss.
  (a) high, high
  (b) low, high
  (c) high, low
  (d) low, low
  Ans: c
10. The rate of rise of current through an inductive coil is maximum
  (a) at 63.2% of its maximum steady value
  (b) at the start of the current flow
  (c) after one time constant
  (d) near the final maximum value of current
  Ans: b
11. When both the inductance and resistance of a coil are doubled the value of
  (a) time constant remains unchanged
  (b) initial rate of rise of current is doubled
  (c) final steady current is doubled
  (d) time constant is halved
  Ans: a
12. The initial rate of rise of current through a coil of inductance 10 H when suddenly connected to a D.C. supply of 200 V is_______Vs
  (a) 50
  (b) 20
  (c) 0.05
  (d) 500
  Ans: b
13. A material for good magnetic memory should have
  (a) low hysteresis loss
  (b) high permeability
  (c) low retentivity
  (d) high retentivity
  Ans: d
14. Conductivity is analogous to
  (a) retentivity
  (b) resistivity
  (c) permeability
  (d) inductance
  Ans: c
15. In a magnetic material hysteresis loss takes place primarily due to
  (a) rapid reversals of its magnetisation
  (b) flux density lagging behind magnetising force
  (c) molecular friction
  (d) it high retentivity
  Ans: d
16. Those materials are well suited for making permanent magnets which have _____ retentivity and _______ coercivity.
  (a) low, high
  (b) high, high
  (c) high, low
  (d) low, low
  Ans: b
17. If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be
  (a) zero
  (b) small
  (c) large
  (d) none of the above
  Ans: c
18. Hard steel is suitable for making permanent magnets because
  (a) it has good residual magnetism
  (b) its hysteresis loop has large area
  (c) its mechanical strength is high
  (d) its mechanical strength is low
  Ans: a
19. Silicon steel is used in electrical machines because it has
  (a) low coercivity
  (b) low retentivity
  (c) low hysteresis loss
  (d) high coercivity
  Ans: c
20. Conductance is analogous to
  (a) permeance
  (b) reluctance
  (c) flux
  (d) inductance
  Ans: a
21. The property of a material which opposes the creation of magnetic flux in it is known as
  (a) reluctivity
  (b) magnetomotive force
  (c) permeance
  (d) reluctance
  Ans: d
22. The unit of retentivity is
  (a) weber
  (b) weber/sq. m
  (c) ampere turn/meter
  (d) ampere turn
  Ans: b
23. Reciprocal of reluctance is
  (a) reluctivity
  (b) permeance
  (c) permeability
  (d) susceptibility
  Ans: b
24. While comparing magnetic and electric circuits, the flux of magnetic circuit is compared with which parameter of electrical circuit ?
  (a) E.m.f.
  (b) Current
  (c) Current density
  (d) Conductivity
  Ans: b
25. The unit of reluctance is
  (a) metre/henry
  (b) henry/metre
  (c) henry
  (d) 1/henry
  Ans: d
26. A ferrite core has less eddy current loss than an iron core because
  (a) ferrites have high resistance
  (b) ferrites are magnetic
  (c) ferrites have low permeability
  (d) ferrites have high hysteresis
  Ans: a
27. Hysteresis loss least depends on
  (a) volume of material
  (b) frequency
  (c) steinmetz coefficient of material
  (d) ambient temperature
  Ans: d
28. Laminated cores, in electrical machines, are used to reduce
  (a) copper loss
  (b) eddy current loss
  (c) hysteresis loss
  (d) all of the above
  Ans: b
Electromagnetic Induction
1. The property of coil by which a counter e.m.f. is induced in it when the current through the coil changes is known as
  (a) self-inductance
  (b) mutual inductance
  (c) series aiding inductance
  (d) capacitance
  Ans: a
2. As per Faraday’s laws of electromagnetic induction, an e.m.f. is induced in a conductor whenever it
  (a) lies perpendicular to the magnetic flux
  (b) lies in a magnetic field
  (e) cuts magnetic flux
  (d) moves parallel to the direction of the magnetic field
  Ans: c
3. Which of the following circuit element stores energy in the electromagnetic field ?
  (a) Inductance
  (b) Condenser
  (c) Variable resistor
  (d) Resistance
  Ans: a
4. The inductance of a coil will increase under all the following conditions except
  (a) when more length for the same number of turns is provided
  (6) when the number of turns of the coil increase
  (c) when more area for each turn is provided
  (d) when permeability of the core increases
  Ans: a
5. Higher the self-inductance of a coil,
  (a) lesser its weber-turns
  (b) lower the e.m.f. induced
  (c) greater the flux produced by it
  (d) longer the delay in establishing steady current through it
  Ans: d
6. In an iron cored coil the iron core is removed so that the coil becomes an air cored coil. The inductance of the coil will
  (a) increase
  (b) decrease
  (c) remain the same
  (d) initially increase and then decrease
  Ans: b
7. An open coil has
  (a) zero resistance and inductance
  (b) infinite resistance and zero inductance
  (c) infinite resistance and normal inductance
  (d) zero resistance and high inductance
  Ans: b
8. Both the number of turns and the core length of an inductive coil are doubled.
  Its self-inductance will be
  (a) unaffected
  (b) doubled
  (c) halved
  (d) quadrupled
  Ans: b
9. If current in a conductor increases then according to Lenz’s law self-induced voltage will
  (a) aid the increasing current
  (b) tend to decrease the amount of cur-rent
  (c) produce current opposite to the in-creasing current
  (d) aid the applied voltage
  Ans: c
10. The direction of induced e.m.f. can be found by
  (a) Laplace’s law
  (b) Lenz’s law
  (c) Fleming’s right hand rule
  (d) Kirchhoff s voltage law
  Ans: b
11. Air-core coils are practically free from
  (a) hysteresis losses
  (b) eddy current losses
  (c) both (a) and (b)
  (d) none of the above
  Ans: c
12. The magnitude of the induced e.m.f. in a conductor depends on the
  (a) flux density of the magnetic field
  (b) amount of flux cut
  (c) amount of flux linkages
  (d) rate of change of flux-linkages
  Ans: d
13. Mutually inductance between two magnetically-coupled coils depends on
  (a) permeability of the core
  (b) the number of their turns
  (c) cross-sectional area of their common core
  (d) all of the above
  Ans: d
14. A laminated iron core has reduced eddy-current losses because
  (a) more wire can be used with less D.C. resistance in coil
  (b) the laminations are insulated from each other
  (c) the magnetic flux is concentrated in the air gap of the core
  (d) the laminations are stacked vertfcally
  Ans: b
15. The law that the induced e.m.f. and current always oppose the cause producing them is due to
  (a) Faraday
  (b) Lenz
  (c) Newton
  (d) Coulomb
  Ans: b
16. Which of the following is not a unit of inductance ?
  (a) Henry
  (b) Coulomb/volt ampere
  (c) Volt second per ampere
  (d) All of the above
  Ans: b
17. In case of an inductance, current is proportional to
  (a) voltage across the inductance
  (b) magnetic field
  (c) both (a) and (b)
  (d) neither (a) nor (b)
  Ans: b
18. Which of the following circuit elements will oppose the change in circuit current ?
  (a) Capacitance
  (b) Inductance
  (c) Resistance
  (d) All of the above
  Ans: b
19. For a purely inductive circuit which of the following is true ?
  (a) Apparent power is zero
  (b) Relative power is.zero
  (c) Actual power of the circuit is zero
  (d) Any capacitance even if present in the circuit will not be charged
  Ans: c
20. Which of the following is unit of inductance ?
  (a) Ohm
  (b) Henry
  (c) Ampere turns
  (d) Webers/metre
  Ans: b
21. An e.m.f. of 16 volts is induced in a coil of inductance 4H. The rate of change of current must be
  (a) 64 A/s
  (b) 32 A/s
  (c) 16 A/s
  (d) 4 A/s
  Ans: d
22. The core of a coil has a length of 200 mm. The inductance of coil is 6 mH. If the core length is doubled, all other quantities, remaining the same, the inductance will be
  (a) 3 mH
  (b) 12 mH
  (c) 24mH
  (d)48mH
  Ans: a
23. The self inductances of two coils are 8 mH and 18 mH. If the co-efficients of coupling is 0.5, the mutual inductance of the coils is
  (a) 4 mH
  (b) 5 mH
  (c) 6 mH
  (d) 12 mH
  Ans: c
24. Two coils have inductances of 8 mH and 18 mH and a co-efficient of coupling of 0.5. If the two coils are connected in series aiding, the total inductance will be
  (a) 32 mH
  (b) 38 mH
  (c) 40 mH
  (d) 48 mH
  Ans: b
25. A 200 turn coil has an inductance of 12 mH. If the number of turns is increased to 400 turns, all other quantities (area, length etc.) remaining the same, the inductance will be
  (a) 6 mH
  (b) 14 mH
  (c) 24 mH
  (d) 48 mH
  Ans: d
26. Two coils have self-inductances of 10 H and 2 H, the mutual inductance being zero. If the two coils are connected in series, the total inductance will be
  (a) 6 H
  (b) 8 H
  (c) 12 H
  (d) 24 H
  Ans: c
27. In case all the flux from the current in coil 1 links with coil 2, the co-efficient of coupling will be
  (a) 2.0
  (b) 1.0
  (c) 0.5
  (d) zero
  Ans: b
28. A coil with negligible resistance has 50V across it with 10 mA. The inductive reactance is
  (a) 50 ohms
  (b) 500 ohms
  (c) 1000 ohms
  (d) 5000 ohms
  Ans: d
29. A conductor 2 meters long moves at right angles to a magnetic field of flux density 1 tesla with a velocity of 12.5 m/s. The induced e.m.f. in the conductor will be
  (a) 10 V
  (6) 15 V
  (c) 25V
  (d) 50V
  Ans: c
s: d

Lenz’s law is a consequence of the law of conservation of
(a) induced current
(b) charge
(c) energy
(d) induced e.m.f.
Ans: c
A conductor carries 125 amperes of current under 60° to a magnetic field of 1.1 tesla. The force on the conductor will be
nearly
(a) 50 N
(b) 120 N
(c) 240 N
(d) 480 N
Ans: b
Find the force acting on a conductor 3m long carrying a current of 50 amperes at right angles to a magnetic field having a flux density of 0.67 tesla.
(a) 100 N
(b) 400 N
(c) 600 N
(d) 1000 N
Ans: a
The co-efficient of coupling between two air core coils depends on
(a) self-inductance of two coils only
(b) mutual inductance between two coils only
(c) mutual inductance and self inductance of two coils
(d) none of the above
Ans: c
An average voltage of 10 V is induced in a 250 turns solenoid as a result of a change in flux which occurs in 0.5 second. The total flux change is
(a) 20 Wb
(b) 2 Wb
(c) 0.2 Wb
(d) 0.02 Wb
Ans: d
A 500 turns solenoid develops an average induced voltage of 60 V. Over what time interval must a flux change of 0.06 Wb occur to produce such a voltage ?
(a) 0.01 s
(b) 0.1 s
(c) 0.5 s
(d) 5 s
Ans: c
Which of the fpllowing inductor will have the least eddy current losses ?
(a) Air core
(b) Laminated iron core
(c) Iron core
(d) Powdered iron core
Ans: a
A coil induces 350 mV when the current changes at the rate of 1 A/s. The value of inductance is
(a) 3500 mH
(b) 350 mH
(c) 250 mH
(d) 150 mH
Ans: b
Two 300 uH coils in series without mutual coupling have a total inductance of
(a) 300 uH
(b) 600 uH
(c) 150 uH
(d) 75 uH
Ans: b
Current changing from 8 A to 12 A in one second induced 20 volts in a coil.
The value of inductance is
(a) 5 mH
(b) 10 mH
(c) 5 H
(d) 10 H
Ans: c
Which circuit element(s) will oppose the change in circuit current ?
(a) Resistance only
(b) Inductance only
(c) Capacitance only
(d) Inductance and capacitance
Ans: b
A crack in the magnetic path of an inductor will result in
(a) unchanged inductance
(b) increased inductance
(c) zero inductance
(d) reduced inductance
Ans: d
A coil is wound on iron core which carries current I. The self-induced voltage in the coil is not affected by
(a) variation in coil current
(b) variation in voltage to the coil
(c) change of number of turns of coil
(d) the resistance of magnetic path
Ans: b
A moving magnetic field will produce the same effect as a conductor that is moving.
(a) Yes
(b) No
Ans:
The polarity of the induced voltage can be determined by using the left-hand generator rule.
(a) Yes
(b) No
Ans: a
Increasing the field or increasing the current will decrease the force on the conductor.
(a) Yes
(b) No
Ans: b
Reversing the field or the current will reverse the force on the conductor.
(a) Yes
(b) No
Ans: a
When a conductor moves in the field, so that it makes an angle 8 with the lines of flux, the force F is given as : F = Bl sin2 0.
(a) Yes
(b) No
Ans: b
The self-inductance of the coil may be defined as equal to the e.m.f. induced in volts when the current in the circuit changes at the rate of unit Weber turns.
(a) Yes
(b) No
Ans: b

ELECTROLYSIS and STORAGE of BATTERIES

“The mass of an ion liberated at an electrode is directly proportional to the quantity of electricity”.
The above statement is associated with
(a) Newton’s law
(b) Faraday’s law of electromagnetic
(c) Faraday’s law of electrolysis
(d) Gauss’s law
Ans: c
The charge required to liberate one gram equivalent of any substance is known as ______ constant
(a) time
(b) Faraday’s
(c) Boltzman
Ans: b
During the charging of a lead-acid cell
(a) its voltage increases
(b) it gives out energy
(c) its cathode becomes dark chocolate brown in colour
(d) specific gravity of H2SO4 decreases
Ans: a
The capacity of a lead-acid cell does not depend on its
(a) temperature
(b) rate of charge
(c) rate of discharge
(d) quantity of active material
Ans: b
During charging the specific gravity of the electrolyte of a lead-acid battery
(a) increases
(b) decreases
(c) remains the same
(d) becomes zero
Ans: a
The active materials on the positive and negative plates of a fully charged lead-acid battery are
(a) lead and lead peroxide
(b) lead sulphate and lead
(c) lead peroxide and lead
(d) none of the above
Ans: c
When a lead-acid battery is in fully charged condition, the color of its positive plate is
(a) dark grey
(b) brown
(c) dark brown
(d) none of above
Ans: c
The active materials of a nickel-iron battery are
(a) nickel hydroxide
(6) powdered iron and its oxide
(c) 21% solution of KOH
(d) all of the above
Ans: d
The ratio of ampere-hour efficiency to watt-hour efficiency of a lead-acid cell is
(a) just one
(b) always greater than one
(c) always less than one
(d) none of the above.
Ans: b
The best indication about the state of charge on a lead-acid battery is given by
(a) output voltage
(b) temperature of electrolyte
(c) specific gravity of electrolyte
(d) none of the above
Ans: c
The storage battery generally used in electric power station is
(a) nickel-cadmium battery
(b) zinc-carbon battery
(c) lead-acid battery
(d) none of the above
Ans: c
The output voltage of a charger is
(a) less than the battery voltage
(b) higher than the battery voltage
(c) the same as the battery voltage
(d) none of the above
Ans: b
Cells are connected in series in order to
(a) increase the voltage rating
(6) increase the current rating
(c) increase the life of the cells
(d) none of the above
Ans: a
Five 2 V cells are connected in parallel.
The output voltage is
(a) 1 V
(6) 1.5 V
(c) 1.75 V
(d) 2 V
Ans: d
The capacity of a battery is expressed in terms of
(a) current rating
(b) voltage rating
(e) ampere-hour rating
(d) none of the above
Ans: c
During the charging and discharging of a nickel-iron cell
(a) corrosive fumes are produced
(b) water is neither formed nor absorbed
(c) nickel hydroxide remains unsplit
(d) its e.m.f. remains constant
Ans: b
As compared to constant-current system, the constant-voltage system of charging a lead acid cell has the advantage of
(a) reducing time of charging
(b) increasing cell capacity
(c) both (a) and (b)
(d) avoiding excessive gassing
Ans: c
A dead storage battery can be revived by
(a) adding distilled water
(6) adding so-called battery restorer
(c) a dose of H2SO4
(d) none of the above
Ans: d
As compared to a lead-acid cell, the efficiency of a nickel-iron cell is less due to its
(a) compactness
(b) lower e.m.f.
(c) small quantity of electrolyte used
(d) higher internal resistance
Ans: d
Trickle charging of a storage battery helps to
(a) maintain proper electrolyte level
(b) increase its reserve capacity
(c) prevent sulphation
(d) keep it fresh and fully charged
Ans: d
Those substances of the cell which take active part in chemical combination and hence produce electricity during charging or discharging are known as______materials.
(a) passive
(b) active
(c) redundant
(d) inert
Ans: b
In a lead-acid cell dilute sulfuric acid (electrolyte) approximately comprises the following
(a) one part H2O, three parts H2SO4
(b) two parts H2O, two parts H2SO4
(c) three parts H2O, one part H2SO4
(d) all H2S04
Ans: c
It is noticed that durum charging
(a) there is a rise in voltage
(6) energy is absorbed by the cell
(c) specific gravity of H2SO4 is increased
(d) the anode becomes chocolate brown in colour (PbCfe) and cathode becomes grey metallic lead (Pb)
(e) all of the above
Ans: e
It is noticed that during discharging the following does not happen
(a) both anode and cathode become PbS04
(b) specific gravity of H2SO4 decreases
(c) voltage of the cell decreases
(d) the cell absorbs energy
Ans: d
The ampere-hour efficiency of a leadacid cell is normally between
(a) 20 to 30%
(b) 40 to 50%
(c) 60 to 70%
(d) 90 to 95%
Ans: d
The watt-hour efficiency of a lead-acid cell varies between
(a) 25 to 35%
(b) 40 to 60%
(c) 70 to 80%
(d) 90 to 95%
Ans: c
The capacity of a lead-acid cell is measured in
(a) amperes
(b) ampere-hours
(c) watts
(d) watt-hours
Ans: b
The capacity of a lead-acid cell depends on
(a) rate of discharge
(b) temperature
(c) density of electrolyte
(d) quantity of active materials
(e) all above
Ans: e
When the lead-acid cell is fully charged, the electrolyte assumes _____ appearance
(a) dull
(b) reddish
(c) bright
(d) milky
Ans: d
The e.m.f. of an Edison cell, when fully charged, is nearly
(a) 1.4 V
(b) 1 V
(c) 0.9 V
(d) 0.8 V
Ans: a
The internal resistance of an alkali cell is nearly _____ times that of the lead-acid cell.
(a) two
(b) three
(c) four
(d) five
Ans: d
The average charging voltage for alkali cell is about
(a) 1 V
(b) 1.2 V
(c) 1.7 V
(d) 2.1 V
Ans: c
On the average the ampere-hour efficiency of an Edison cell is about
(a) 40%
(b) 60%
(c) 70%
(d) 80%
Ans: d
The active material of the positive plates of silver-zinc batteries is
(a) silver oxide
(b) lead oxide
(c) lead
(d) zinc powder
Ans: a
Lead-acid cell has a life of nearly charges and discharges
(a) 500
(b) 700
(c) 1000
(d) 1250
Ans: d
Life of the Edison cell is at least
(a) five years
(b) seven years
(c) eight years
(d) ten years
Ans: a
The internal resistance of a lead-acid cell is that of Edison cell
(a) less than
(b) more than
(c) equal to
(d) none of the above
Ans: a
Electrolyte used in an Edison cell is
(a) NaOH
(b) KOH
(c) HC1
(d) HN03
Ans: b
Electrolyte used in a lead-acid cell is
(a) NaOH
(b) onlyH2S04
(c) only water
(d) dilute H2SO4
Ans: d
Negative plate of an Edison cell is made of
(a) copper
(b) lead
(c) iron
(d) silver oxide
Ans: c
The open circuit voltage of any storage cell depends wholly upon
(a) its chemical constituents
(b) on the strength of its electrolyte
(c) its temperature
(d) all above
Ans: d
The specific gravity of electrolyte is measured by
(a) manometer
(6) a mechanical gauge
(c) hydrometer
(d) psychrometer
Ans: c
When the specific gravity of the electrolyte of a lead-acid cell is reduced to 1.1 to 1.15 the cell is in
(a) charged state
(b) discharged state
(c) both (a) and (b)
(d) active state
Ans: b
In ______ system the charging current is intermittently controlled at either a maximum or minimum value
(a) two rate charge control
(b) trickle charge
(c) floating charge
(d) an equalizing charge
Ans: a
Over charging
(a) produces excessive gassing
(b) loosens the active material
(e) increases the temperature resulting in buckling of plates
(d) all above
Ans: d
Undercharging
(a) reduces specific gravity of the electrolyte
(b) increases specific gravity of the electrolyte
(c) produces excessive gassing
(d) increases the temperature
Ans: a
Internal short circuits are caused by
(a) breakdown of one or more separators
(b) excess accumulation of sediment at the bottom of the cell
(c) both (a) and (b)
(d) none of the above
Ans: c
The effect of sulphation is that the internal resistance
(a) increases
(b) decreases
(c) remains same
(d) none of the above
Ans: a
Excessive formation of lead sulphate on the surface of the plates happens because of
(a) allowing a battery to stand in discharged condition for a long time
(b) topping up with electrolyte
(c) persistent undercharging
(d) low level of electrolyte
(e) all above
Ans: e
The substances which combine together to store electrical energy during the charge are called ______ materials
(a) active
(b) passive
(c) inert
(d) dielectric
Ans: a
In a lead-acid cell, lead is called as
(a) positive active material
(b) negative active material
(c) passive material
(d) none of the above
Ans: b
The lead-acid cell should never be discharged beyond
(a) 1.8 V
(b) 1.9 V
(c) 2 V
(d) 2.1 V
Ans: a
On overcharging a battery
(a) it will bring about chemical change in active materials
(b) it will increase the capacity of the battery
(c) it will raise the specific gravity of the electrolyte
(d) none of the above will occur
Ans: d
Each cell has a vent cap
(a) to allow gases out when the cell is on charge
(b) to add water to the cell if needed
(c) to check the level of electrolyte
(d) to do all above functions
Ans: d
Following will occur if level of electrolyte falls below plates
(a) capacity of the cell is reduced
(b) life of the cell is reduced
(c) open plates are converted to lead sulphate
(d) all above
Ans: d
In constant voltage charging method, the charging current from discharged to fully charged condition
(a) decreases
(b) increases
(c) remains constant
(d) none of the above
Ans: a
48 ampere-hour capacity would deliver a current of
(a) 48 amperes for 1 hour
(b) 24 amperes for 2 hours
(c) 8 amperes for 6 hours
(d) 6 amperes for 8 hours
Ans: d
In constant-current charging method, the supply voltage from discharged to
fully charged condition
(a) decreases
(b) increases
(c) remains constant
(d) none of the above
Ans: b
Battery charging equipment is generally installed
(a) in well ventilated location
(b) in clean and dry place
(c) as near as practical to the battery being charged
(d) in location having all above features
Ans: d
Following will happen if the specific gravity of electrolyte becomes more than 1.23.
(a) Loss of capacity
(b) Loss of life
(c) Corrosion of the grids of the plate
(d) All above
Ans: d
Batteries are charged by
(a) rectifiers
(b) engine generator sets
(c) motor generator sets
(d) any one of the above methods
Ans: d
Cell short circuit results in
(a) low sp. gravity electrolyte
(b) abnormal high temperature
(c) reduced gassing on charge
(d) all above
Ans: d
Internal resistance of a cell is reduced by
(a) using vent plug to permit gas formed during discharge
(b) increasing the plate area
(c) putting plates very close together
(d) all above methods
Ans: d
Capacity of dry cells is
(a) more when it is supplying current for intermittent periods
(b) more when it is supplying current for continuous periods
(c) unaffected by the type of discharge
(d) none of the above
Ans: a
Battery container should be acid resistance, therefore it is made up of
(a) glass
(b) plastic
(c) wood
(d) all above
Ans: d
Sulphated cells are indicated by
(a) the loss of capacity of the cell
(6) the decrease of the specific gravity
(c) the low voltage of the cell on discharge
(d) all above conditions
Ans: d
In a lead-acid cell, if the specific gravity of sulphuric acid is 1.8, it will require following ratio of acid to water to get mixture of specific gravity of 1.3
(a) 6 parts of acid to 4 parts of water
(b) 4 parts of acid to 4 parts of water
(c) 4 parts of acid to 6 parts of water
(d) 4 parts of acid to 8 parts of water
Ans: c
Local action in a battery is indicated by
(a) excessive gassing under load conditions
(b) excessive drop in the specific gravity of electrolyte even when the cell is on open circuit
(c) both (a) and (b)
(d) none of the above
Ans: d
Following will happen if battery charging rate is too high
(a) excessive gassing will occur
(b) temperature rise will occur
(c) bulging and buckling of plates will occur
(d) all above will occur
Ans: d
Internal resistance of a cell is due to
(a) resistance of electrolyte
(b) electrode resistance
(c) surface contact resistance between electrode and electrolyte
(d) all above
Ans: d
If a battery is wrongly connected on charge following will happen
(a) current delivered by the battery will be high
(b) current drawing will be nil
(c) current drawing will be very small
(d) current drawing will be very high
Ans: d
In order that a hydrometer may float vertically in electrolyte its C.G. should be
(a) lowered
(b) raised
(c) undisturbed
(d) displaced sideways
Ans: a
If a lead-acid cell is discharged below 1.8 V the following will happen.
(a) Capacity of cell will reduce
(b) Sulphation of plates will occur
(c) Internal resistance will increase
(d) All above will occur
Ans: d
Life of the batteries is in the following ascending order.
(a) Lead-acid cell, Edison cell, Nickel cadmium cell
(b) Lead-acid cell, Nickel-cadmium cell, Edison cell
(c) Edison cell, Nickel-cadmium cell, lead-acid cell
(d) Nickel-cadmium cell, Edison cell, lead-acid cell
Ans: a
Persons preparing electrolyte should wear
(a) goggles or other face shield
(b) rubber
(c) rubber boots and gloves
(d) all above safety devices
Ans: d
Excessive charging a battery tends to
(a) produce gassing
(b) increase the internal resistance of the battery
(c) to corrode the positive plates into lead peroxide thereby weakening them physically
(d) bring about all above changes
Ans: d
Shelf life of a small dry cell is
(a) equal to that of large dry cell
(6) less than that of large dry cell
(c) more than that of large dry cell
(d) none of the above
Ans: b
The current flow through electrolyte is due to the movement of
(a) ions
(b) holes
(c) electrons
(d) none of the above
Ans: a
Level of electrolyte in a cell should be _____ the level of plates
(a) below
(b) equal to
(c) above
(d) none of the above
Ans: c
During discharge, the active material of both the positive and negative plates is changed to
(a) Pb
(b) Pb02
(c) PbO
(d) PbS04
Ans: d

81 _____ of electrolyte indicates the state of charge of the battery
(a) colour
(b) mass
(c) viscosity
(d) specific gravity
Ans: d

The following indicate that battery on charge has attained full charge
(a) colour of electrode
(b) gassing
(c) specific gravity
(d) all above
Ans: d
Dry cell is modification of
(a) Deniell cell
(b) Leclanche cell
(e) Lead-acid cell
(d) Edison cell
Ans: b
Capacity of a battery.is expressed in
(a) Ah
(b) Vh
(c) Wh
(d) kWh
Ans: a
In alkaline cell the electrolyte is
(a) dilute sulphuric acid
(b) concentrated sulphuric acid
(c) NaOH
(d) KOH
Ans: d
Self charge of a Ni-Fe cell is _____ Edison cell.
(a) equal to
(b) less than
(c) more than
(d) much more than
Ans: b
Ampere hour capacity of an industrial battery is based on ____ hours discharge rate.
(a) 8
(b) 12
(c) 16
(d) 24
Ans: a
The body of Edison cell is made of
(a) bakelite
(b) rubber
(c) nickel plated steel
(d) aluminium
Ans: c
Specific gravity of electrolyte in Edison cell is
(a) 0.8
(b) 0.95
(c) 1.1
(d) 1.21
Ans: d
All the electrical connections between the battery and vehicle should be by
(a) thin aluminium wires
(b) thin copper wires
(c) rigid cables
(d) flexible cables
Ans: d
A battery of 6 cells will show a drop of _____ volts from fully charged state to fully discharged state.
(a) 1.0
(b) 1.5
(c) 2.4
(d) 2.9
Ans: c
During the idle period of the battery, strong electrolyte tends to change the active material of the cell into
(a) Pb02
(6) PbSC-4
(c) PbO
(d) Pb
Ans: b
Chargmg of sulphated battery produces ____ heat.
(a) no
(b) very little
(c) less
(d) more
Ans: d
Hydrogen evolved during charging produces explosive mixture when it is more than
(a) 2%
(b) 4%
(c) 6%
(d) 8%
Ans: d
Weston standard cell at 20°C has voltage of ____ volts.
(a) 0.8
(b) 0.9
(c) 1.0187
(d) 1.5
Ans: c
Extent of corrosion in the underground metal work depends upon
(a) amount of moisture
(b) type of metals
(c) type of soil chemicals
(d) all above factors
Ans: d
Mercury cell has which of the following characteristics ?
(a) Flat discharge current-voltage curve
(6) High power to weight ratio
(c) Comparatively longer shelf life under adverse conditions of high temperature and humidity
(d) All of the above
Ans: d
Charging a sulphated battery at high rate results in
(a) boiling of electrolyte due to gassing
(b) warping of plates
(c) damage to separators, cell caps covers and battery case due to excessive temperature
(d) all above
Ans: d
Short circuiting of a cell may be caused
(a) buckling of plates
(b) faulty separators
(c) lead particles forming circuit between positive and negative plates
(d) excessive accumulation of sediment
(e) any one of above
Ans: e
In a battery cover is placed over the element and sealed to the top of the battery container. This is done
(a) to reduce evaporation of water from electrolyte
(b) to exclude dirt and foreign matter from the electrolyte
(c) to discharge both of the above functions
(d) to discharge none of the above functions
Ans: c
For a cell to work, which of the following condition(s) become necessary ?
(a) Two electrodes of different meta’s should be inserted in the electrolyte, not touching each other
(b) Electrolyte must chemically react with one of the electrodes
(c) Electrolyte liquid or paste should be conducting
(d) All above three conditions are necessary
Ans: d
Which of the following primary cells has the lowest voltage ?
(a) Lithium
(b) Zinc-chloride
(c) Mercury
(d) Carbon-zinc
Ans: c
Which of the following primary cells has the highest voltage ?
(a) Manganese-alkaline
(6) Carbon-zinc
(c) Lithium
(d) Mercury
Ans: c
While preparing electrolyte for a lead-acid battery
(a) water is poured into acid
(b) acid is poured into water
(c) anyone of the two can be added to other chemical
Ans: b
Which of the following battery is used for air-craft ?
(a) Lead-acid battery
(b) Nickel-iron battery
(c) Dry cell battery
(d) Silver oxide battery
Ans: b
Which of the following cell has a. reversible chemical reaction ?
(a) Lead-acid
(b) Mercury oxide
(c) Carbon-zinc
(d) Silver-oxide
Ans: a
Which of the following is incorrect ?
(a) A storage cell has a reversible chemical reaction
(b) A lead-acid cell can be recharged
(c) A carbon-zinc cell has unlimited shelf life
(d) A primary cell has an irreversible chemical reaction
Ans: c
Which of the following has lower sp. gravity V
(a) Dilute H2S04
(6) Concentrated H2SO4
(c) Water
(d) Any of the above
Ans: c
Under normal charging rate, the charging current should be
(a) 10% of capacity
(b) 20% of capacity
(c) 30% of capacity
(d) 40% of capacity
Ans: a
When two batteries are connected in parallel, it should be ensured that
(a) they have same e.m.f.
(b) they have same make
(c) they have same ampere-hour capacity
(d) they have identical internal resistance
Ans: a
A typical output of a solar cell is
(a) 0.1V
(b) 0.26 V
(c) 1.1 V
(d) 2 V
Ans: b
Petroleum jelly is applied to the electrical connections to the lead-acid battery
(a) prevent local heating
(b) prevent short-circuiting
(c) reduce path resistance
(d) prevent corrosion
Ans: d
When the load resistance equals the generator resistance which of the following will be maximum ?
(a) Current
(b) Efficiency of the circuit
(c) Power in the load resistance
(d) Voltage across the load resistance
Ans: c
The common impurity in the electrolyte of lead-acid battery is
(a) chlorine
(b) dust particles
(c) lead crystals
(d) iron
Ans: d
In a lead-acid battery the energy is stored in the form of
(a) charged ions
(b) chemical energy
(c) electrostatic energy
(d) electromagnetic energy
Ans: b
Which among the following constitutes the major load for an automobile battery ?
(a) Brake light
(b) Self starter
(c) Parking lights
(d) Spark plugs
Ans: b
Which of the following factors adversely affects the capacity of the leadacid battery ?
(a) Temperature of surroundings
(b) Specific gravity of electrolyte
(c) Rate of discharge
(d) All of the above
Ans: d
Cells are connected in parallel to
(a) increase the efficiency
(b) increase the current capacity
(c) increase the voltage output
(d) increase the internal resistance
Ans: b
A constant-voltage generator has
(a) minimum efficiency
(b) minimum current capacity
(c) low internal resistance
(d) high internal resistance
Ans: c
Satellite power requirement is provided through
(a) solar cells
(b) dry cells
(c) nickel-cadmium cells
(d) lead-acid batteries
Ans: a

EEE Multiple choice Questions with Answers

Network Theorems

Kirchhoff s current law states that
(a) net current flow at the junction is positive
(b) Hebraic sum of the currents meeting at the junction is zero
(c) no current can leave the junction without some current entering it.
(d) total sum of currents meeting at the junction is zero
Ans: b
According to Kirchhoffs voltage law, the algebraic sum of all IR drops and e.m.fs. in any closed loop of a network is always
(a) negative
(b) positive
(c) determined by battery e.m.fs.
(d) zero
Ans: d
Kirchhoffs current law is applicable to only
(a) junction in a network
(b) closed loops in a network
(c) electric circuits
(d) electronic circuits
Ans: a
Kirchhoffs voltage law is related to
(a) junction currents
(b) battery e.m.fs.
(c) IR drops
(d) both (b) and (c)
(e) none of the above
Ans: d
Superposition theorem can be applied only to circuits having
(a) resistive elements
(b) passive elements
(c) non-linear elements
(d) linear bilateral elements
Ans: d
The concept on which Superposition theorem is based is
(a) reciprocity
(b) duality
(c) non-linearity
(d) linearity
Ans: d
Thevenin resistance Rth is found
(a) by removing voltage sources along with their internal resistances
(6) by short-circuiting the given two terminals
(c) between any two ‘open’ terminals
(d) between same open terminals as for Etk
Ans: d
An ideal voltage source should have
(a) large value of e.m.f.
(b) small value of e.m.f.
(c) zero source resistance
(d) infinite source resistance
Ans: c
For a voltage source
(a) terminal voltage is always lower than source e.m.f.
(b) terminal voltage cannot be higher than source e.m.f.
(c) the source e.m.f. and terminal voltage are equal
Ans: b
To determine the polarity of the voltage drop across a resistor, it is necessary to know
(a) value of current through the resistor
(b) direction of current through the resistor
(c) value of resistor
(d) e.m.fs. in the circuit
Ans: b
“Maximum power output is obtained from a network when the load resistance is equal to the output resistance of the network as seen from the terminals of the load”. The above statement is associated with
(a) Millman’s theorem
(b) Thevenin’s theorem
(c) Superposition theorem
(d) Maximum power transfer theorem
Ans: d
“Any number of current sources in parallel may be replaced by a single current source whose current is the algebraic sum of individual source currents and source resistance is the parallel combination of individual
source resistances”.
The above statement is associated with
(a) Thevenin’s theorem
(b) Millman’s theorem
(c) Maximum power transfer theorem
(d) None of the above
Ans: b
“In any linear bilateral network, if a source of e.m.f. E in any branch produces a current I in any other branch, then same e.m.f. acting in the second branch would produce the same current / in the first branch”.
The above statement is associated with
(a) compensation theorem
(b) superposition theorem
(c) reciprocity theorem
(d) none of the above
Ans: c
Which of the following is non-linear circuit parameter ?
(a) Inductance
(b) Condenser
(c) Wire wound resistor
(d) Transistor
Ans: a
A capacitor is generally a
(a) bilateral and active component
(b) active, passive, linear and nonlinear component
(c) linear and bilateral component
(d) non-linear and active component
Ans: c
“In any network containing more than one sources of e.m.f. the current in any branch is the algebraic sum of a number of individual fictitious currents (the number being equal to the number of sources of e.m.f.), each of which is due to separate action of each source of e.m.f., taken in order, when the remaining sources of e.m.f. are replaced by conductors, the resistances of which are equal to the internal resistances of the respective sources”.
The above statement is associated with
(a) Thevenin’s theorem
(b) Norton’s theorem
(c) Superposition theorem
(d) None of the above
Ans: c
Kirchhoff s law is applicable to
(a) passive networks only
(b) a.c. circuits only
(c) d.c. circuits only
(d) both a.c. as well d.c. circuits
Ans: d
Kirchhoff s law is not applicable to circuits with
(a) lumped parameters
(b) passive elements
(c) distributed parameters
(d) non-linear resistances
Ans: c
Kirchhoff s voltage law applies to circuits with
(a) nonlinear elements only
(b) linear elements only
(c) linear, non-linear, active and passive elements
(d) linear, non-linear, active, passive, time varying as wells as time-in-variant elements
Ans: d
The resistance LM will be
(a) 6.66 Q
(b) 12 Q
(c) 18Q
(d) 20Q
Ans: a
For high efficiency of transfer of power, internal resistance of the source should be
(a) equal to the load resistance
(b) less than the load resistance
(c) more than the load resistance
(d) none of the above
Ans: b
Efficiency of power transfer when maximum transfer of power c xerosis
(a) 100%
(b) 80%
(c) 75%
(d) 50%
Ans: d
If resistance across LM in Fig. 2.30 is 15 ohms, the value of R is
(a) 10 Q
(6) 20 Q
(c) 30 Q
(d) 40 Q
Ans: c
For maximum transfer of power, internal resistance of the source should be
(a) equal to load resistance
(b) less than the load resistance
(c) greater than the load resistance
(d) none of the above
Ans: a
If the energy is supplied from a source, whose resistance is 1 ohm, to a load of 100 ohms the source will be
(a) a voltage source
(b) a current source
(c) both of above
(d) none of the above
Ans: a
The circuit whose properties are same in either direction is known as
(a) unilateral circuit
(b) bilateral circuit
(c) irreversible circuit
(d) reversible circuit
Ans: b
In a series parallel circuit, any two resistances in the same current path must be in
(a) series with each other
(b) parallel with each other
(c) series with the voltage source.’
(d) parallel with the voltage source
Ans: a
The circuit has resistors, capacitors and semi-conductor diodes. The circuit will be known as
(a) non-linear circuit
(b) linear circuit
(c) bilateral circuit
(d) none of the above
Ans: a
A non-linear network does not satisfy
(a) superposition condition
(b) homogeneity condition
(c) both homogeneity as well as superposition condition
(d) homogeneity, superposition and associative condition
Ans: c
An ideal voltage source has
(a) zero internal resistance
(b) open circuit voltage equal to the voltage on full load
(c) terminal voltage in proportion to current
(d) terminal voltage in proportion to load
Ans: a
A network which contains one or more than one source of e.m.f. is known as
(a) linear network
(b) non-linear network
(c) passive network
(d) active network
Ans: c
The superposition theorem is applicable to
(a) linear, non-linear and time variant responses
(b) linear and non-linear resistors only
(c) linear responses only
(d) none of the above
Ans: c
Which of the following is not a nonlinear element ?
(a) Gas diode
(b) Heater coil
(c) Tunnel diode
(d) Electric arc
Ans:
Application of Norton’s theorem to a circuit yields
(a) equivalent current source and impedance in series
(6) equivalent current source and impedance in parallel
(c) equivalent impedance
(d) equivalent current source
Ans: a
Millman’s theorem yields
(a) equivalent resistance
(6) equivalent impedance
(c) equivalent voltage source
(d) equivalent voltage or current source
Ans: d
The superposition theorem is applicable to
(a) voltage only
(b) current “only
(c) both current and voltage
(d) current voltage and power
Ans: d
Between the branch voltages of a loop the Kirchhoff s voltage law imposes
(a) non-linear constraints
(b) linear constraints
(c) no constraints
(d) none of the above
Ans: b
A passive network is one which contains
(a) only variable resistances
(b) only some sources of e.m.f. in it
(c) only two sources of e.m.f. in it
(d) no source of e.m.f. in it
Ans: d
A terminal where three on more branches meet is known as
(a) node
(b) terminus
(c) combination
(d) anode
Ans: a
Which of the following is the passive element ?
(a) Capacitance
(b) Ideal current source
(c) Ideal voltage source
(d) All of the above
Ans: a
Which of the following is a bilateral element ?
(a) Constant current source
(b) Constant voltage source
(c) Capacitance
(d) None of the above
Ans: c
A closed path made by several branches of the network is known as
(a) branch
(b) loop
(c) circuit
(d) junction
Ans: b
A linear resistor having 0 < R < °o is a
(a) current controlled resistor
(6) voltage controlled resistor
(c) both current controlled and voltage controlled resistor
(d) none of the above
Ans: c
A star circuit has element of resistance R/2. The equivalent delta elements will be
(a) R/6
(b) fi?
(c) 2R
(d) 4R
Ans: b
A delta circuit has each element of value R/2. The equivalent elements of star circuit with be
(a) RIG
(b) R/3
(c) 2R
(d) 3R
Ans: a
In Thevenin’s theorem, to find Z
(a) all independent current sources are short circuited and independent voltage sources are open circuited
(b) all independent voltage sources are open circuited and all independent current sources are short circuited
(c) all independent voltage and current sources are short circuited
(d) all independent voltage sources are short circuited and all independent current sources are open circuited
Ans: d
While calculating Rth in Thevenin’s theorem and Norton equivalent
(a) all independent sources are made dead
(b) only current sources are made dead
(c) only voltage sources are made dead
(d) all voltage and current sources are made dead
Ans: a
The number of independent equations to solve a network is equal to
(a) the number of chords
(b) the number of branches
(c) sum of the number of branches and chords
(d) sum of number of branches, chords and nodes
Ans: a
The superposition theorem requires as many circuits to be solved as there are
(a) sources, nodes and meshes
(b) sources and nodes
(c) sources
(d) nodes
Ans: c
Choose the incorrect statement.
(a) A branch formed by the parallel connection of any resistor R and open circuit has the characteristic of an open circuit.
(b) A branch formed by the parallel connection of any resistor R and a short circuit has the characteristic of a short circuit.
(c) A branch formed by the series connection of any resistor R and an open circuit has the characteristic of an open circuit.
(d) A branch formed by the series connection of any resistor R and a short circuit has the characteristic of resistor R.
Ans: a

Synchronous

Synchronous motors are generally not self-starting because
(a) the direction of rotation is not fixed
(b) the direction of instantaneous torque reverses after half cycle
(c) startes cannot be used on these machines
(d) starting winding is not provided on the machines
Ans: b
In case one phase of a three-phase synchronous motor is short-circuited the motor will
(a) not start
(b) run at 2/3 of synchronous speed
(c) run with excessive vibrations

September 2019
S	S	M	T	W	T	F
« Sep
	1	2	3	4	5	6
7	8	9	10	11	12	13
14	15	16	17	18	19	20
21	22	23	24	25	26	27
28	29	30

EEE Multiple choice Questions with Answers

1. Network Theorems

2. Synchronous Motors

3. Current Electricity

4. A.C. Fundamentals, Circuits & Circuit Theory

5. Circuit Theory

6. D.C. Generators

7. D.C. MOTORS

8. Transformers

9. Polyphase Induction Motors

10. Single Phase Induction Motors

11. Synchronous Motors

12. Rectifiers & Converters

13. Power Plant Engineering

14. Economics of Power Generation

15. Transmission & Distribution

16. Switchgear & Protection

Electrical Engineering Materials

CABLES

Electrical Machine Design

Measurement and Instrumentation

Control Systems

Electric Traction

Industrial Drives

Heating & Welding

Digital Electronics

Circuit Theorems and Conversions

Op-Amp Circuits

Analog Electronics

Semiconductor Theory

Semiconductor Diode

Transistors

Transistor Biasing

Single Stage Transistor Amplifiers

Multistage Transistor Amplifiers

Transistor Audio Power Amplifiers

Op Amp

Hybrid Parameters

Electronic Instruments

Integrated Circuits

Power Electronics

Silicon Controlled Rectifiers

Field Effect Transistors (Fet)

Solid State Switching Circuits

Regulated D.C. Power Supply

Modulation & Demodulation

Transistor Tuned Amplifiers

Oscillators

Parallel Circuits

Electrostatic

Magnetism And Electromagnetism

Magnetic Circuit

Electromagnetic Induction

Electrolysis And Storage Of Batteries

EEE Multiple choice Questions with Answers

Network Theorems

Synchronous

Current Electricity

A.C. Fundamentals, Circuits & Circuit Theory

Circuit Theory

D.C. GENERATORS

D.C. MOTORS

Transformers

Polyphase Induction Motors

Single Phase Induction Motors

Synchronous Motors

Rectifiers & Converters

Power Plant Engineering

Economics of Power Generation

Transmission & Distribution Multiple Choice Questions

Switchgear & Protection

CABLES

Electrical Machine Design

Measurement and Instrumentation

Control Systems

Electric Traction

Industrial Drives

Heating & Welding

Digital Electronics

Circuit Theorems and Conversions