ELECTRICAL100 IMPORTANT EXPECTED MCQ
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Q.1 The two windings of a transformer is
(A) conductively linked.
(B) inductively linked.
(C) not linked at all.
(D) electrically linked.
Ans : B
Q.2 A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will
(A) come to stop.
(B) continue to run at synchronous speed.
(C) continue to run at a speed slightly more than the synchronous speed.
(D) continue to run at a speed slightly less than the synchronous speed.
Ans: B
Q.3 The d. c. series motor should always be started with load because
(A) at no load, it will rotate at dangerously high speed.
(B) it will fail to start.
(C) it will not develop high starting torque.
(D) all are true.
Ans: A
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.4 The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load speed is about
(A) 50 Hz.
(B) 20 Hz.
(C) 2 Hz.
(D) Zero.
Ans: C
Q.5 In a stepper motor the angular displacement
(A) can be precisely controlled.
(B) it cannot be readily interfaced with micro computer based controller.
(C) the angular displacement cannot be precisely controlled.
(D) it cannot be used for positioning of work tables and tools in NC machines.
Ans: A
Q.6 The power factor of a squirrel cage induction motor is
(A) low at light load only.
(B) low at heavy load only.
(C) low at light and heavy load both.
(D) low at rated load only.
Ans: A
Q.7 The generation voltage is usually
(A) between 11 KV and 33 KV.
(B) between 132 KV and 400 KV.
(C) between 400 KV and 700 KV.
(D) None of the above.
Ans: A
Q.8 When a synchronous motor is running at synchronous speed, the damper winding produces
(A) damping torque.
(B) eddy current torque.
(C) torque aiding the developed torque.
(D) no torque.
Ans: D
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.9 If a transformer primary is energised from a square wave voltage source, its output voltage will be
(A) A square wave.
(B) A sine wave.
(C) A triangular wave.
(D) A pulse wave.
Ans: A
Q.14 In a transformer the voltage regulation will be zero when it operates at
(A) unity p.f.
(B) leading p.f.
(C) lagging p.f.
(D) zero p.f.leading.
Ans: B
Q.15 The maximum power in cylindrical and salient pole machines is obtained respectively at load angles of
(A) 90○ ,90○ .
(B) < 90○ ,90○ .
(C) 90○ ,> 90○ .
(D) 90○ , < 90○ .
Ans: D
Q.16 The primary winding of a 220/6 V, 50 Hz transformer is energised from 110 V, 60 Hz supply. The secondary output voltage will be
(A) 3.6 V.
(B) 2.5 V.
(C) 3.0 V.
(D) 6.0 V.
Ans: C
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.17 The emf induced in the primary of a transformer
(A) is in phase with the flux.
(B) lags behind the flux by 90 degree.
(C) leads the flux by 90 degree.
(D) is in phase opposition to that of flux.
Ans: C
Q.18 The relative speed between the magnetic fields of stator and rotor under steady state operation is zero for a
(A) dc machine.
(B) 3 phase induction machine.
(C) synchronous machine.
(D) single phase induction machine.
Ans: all options are correct
Q.19 The current from the stator of an alternator is taken out to the external load circuit through
(A) slip rings.
(B) commutator segments.
(C) solid connections.
(D) carbon brushes.
Ans: C
Q.20 A motor which can conveniently be operated at lagging as well as leading power factors is the
(A) squirrel cage induction motor.
(B) wound rotor induction motor.
(C) synchronous motor.
(D) DC shunt motor.
Ans: C
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.21 A hysteresis motor
(A) is not a self-starting motor.
(B) is a constant speed motor.
(C) needs dc excitation.
(D) can not be run in reverse speed.
Ans: B
Q.22 The most suitable servomotor for low power applications is
(A) a dc series motor.
(B) a dc shunt motor.
(C) an ac two-phase induction motor.
(D) an ac series motor.
Ans: B
Q.23 The size of a conductor used in power cables depends on the
(A) operating voltage.
(B) power factor.
(C) current to be carried.
(D) type of insulation used
Ans: C
Q.24 Out of the following methods of heating the one which is independent of supply frequency is
(A) electric arc heating
(B) induction heating
(C) electric resistance heating
(D) dielectric heating
Ans: C
Q.25 A two-winding single phase transformer has a voltage regulation of 4.5% at full-load and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulation will be
(A) 4.5%.
(B) less than 4.5%.
(C) more than 4.5%.
(D) 4.5% or more than 4.5%.
Ans: C
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.26 In a dc shunt motor the terminal voltage is halved while the torque is kept constant. The resulting approximate variation in speed ‘ w’ and armature current ‘ Ia ‘ will be
(A) Both w and Ia are doubled.
(B) w is constant and Ia is doubled.
(C) w is doubled while Ia is halved.
(D) w is constant but Ia is halved.
Ans: B
Q.27 A balanced three-phase, 50 Hz voltage is applied to a 3 phase, 4 pole, induction motor. When the motor is
delivering rated output, the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the rotor structure is
(A) 1500 r.p.m.
(B) 1425 r.p.m.
(C) 25 r.p.m.
(D) 75 r.p.m.
Ans: D
Q.28 An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging case. If it is required to deliver rated current at rated voltage and 0.8 power-factor leading, the required excitation will be
(A) less.
(B) more.
(C) more or less.
(D) the same.
Ans: B
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.29 A ceiling fan uses
(A) split-phase motor.
(B) capacitor start and capacitor run motor.
(C) universal motor.
(D) capacitor start motor.
Ans: D
Q.30 A stepper motor is
(A) a dc motor.
(B) a single-phase ac motor.
(C) a multi-phase motor.
(D) a two phase motor.
Ans: D
Q.31 The ‘sheath’ is used in cable to
(A) provide strength to the cable.
(B) provide proper insulation.
(C) prevent the moisture from entering the cable.
(D) avoid chances of rust on strands.
Ans: A
Q.32 The drive motor used in a mixer-grinder is a
(A) dc motor.
(B) induction motor.
(C) synchronous motor.
(D) universal motor.
Ans: D
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.33 A 1:5 step-up transformer has 120V across the primary and 600 ohms resistance across the secondary. Assuming 100% efficiency, the primary current equals
(A) 0.2 Amp.
(B) 5 Amps.
(C) 10 Amps.
(D) 20 Amps.
Ans: A
Q.34 A dc shunt generator has a speed of 800 rpm when delivering 20 A to the load at the terminal voltage of 220V. If the same machine is run as a motor it takes a line current of 20A from 220V supply. The speed of the machine as a motor will be
(A) 800 rpm.
(B) more than 800 rpm.
(C) less than 800 rpm.
(D) both higher or lower than 800 rpm.
Ans: C
Q.35 A 50 Hz, 3-phase induction motor has a full load speed of 1440 r.p.m. The number of poles of the motor are
(A) 4.
(B) 6.
(C) 12.
(D) 8.
Ans: A
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q. 36 In a 3-phase synchronous motor
(A) the speed of stator MMF is always more than that of rotor MMF.
(B) the speed of stator MMF is always less than that of rotor MMF.
(C) the speed of stator MMF is synchronous speed while that of rotor MMF is zero.
(D) rotor and stator MMF are stationary with respect to each other.
Ans: D
Q.37 In a capacitor start single-phase induction motor, the capacitor is connected
(A) in series with main winding.
(B) in series with auxiliary winding.
(C) in series with both the windings.
(D) in parallel with auxiliary winding.
Ans: B
Q.38 A synchro has
(A) a 3-phase winding on rotor and a single-phase winding on stator.
(B) a 3-phase winding on stator and a commutator winding on rotor.
(C) a 3-phase winding on stator and a single-phase winding on rotor.
(D) a single-phase winding on stator and a commutator winding on rotor.
Ans: C
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.39 As the voltage of transmission increases, the volume of conductor
(A) increases.
(B) does not change.
(C) decreases.
(D) increases proportionately.
Ans: C
Q.40 The size of the feeder is determined primarily by
(A) the current it is required to carry.
(B) the percent variation of voltage in the feeder.
(C) the voltage across the feeder.
(D) the distance of transmission.
Ans: A
Q.41 The boundary of the protective zone is determined by the
(A) Location of CT
(B) sensitivity of relay used
(C) Location of PT
(D) None of these
Ans: B
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.42 In a three phase transformer, if the primary side is connected in star and secondary side is connected in delta, what is the angle difference between phase voltage in the two cases.
(A) delta side lags by -30°.
(B) star side lags by -30°.
(C) delta side leads by 30°.
(D) star side leads by -30°.
Ans: C
Q.43 To achieve low PT error, the burden value should be .
(A) low
(B) high
(C) medium
(D) none of the above
Ans: A
Q.44 Slip of the induction machine is 0.02 and the stator supply frequency is 50 Hz. What will be the frequency of the rotor induced emf?
(A) 10 Hz.
(B) 50 Hz.
(C) 1 Hz.
(D) 2500 Hz.
Ans: C
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.45 A 4 pole lap wound dc shunt motor rotates at the speed of 1500 rpm, has a flux of 0.4 mWb and the total number of conductors are 1000. What is the value of emf?
(A) 100 Volts.
(B) 0.1 Volts.
(C) 1 Volts.
(D) 10 Volts.
Ans: D
Q.46 The synchronous reactance of the synchronous machine is .
(A) Ratio between open circuit voltage and short circuit current at constant field current
(B) Ratio between short circuit voltage and open circuit current at constant field current
(C) Ratio between open circuit voltage and short circuit current at different field current
(D) Ratio between short circuit voltage and open circuit current at different field current
Ans. A
Q.47 A 3 stack stepper motor with 12 numbers of rotor teeth has a step angle of.
(A) 12°
(B) 8°
(C) 24°
(D) 10°
Ans. D
Q.48 In case of a universal motor, torque pulsation is minimized by _ .
(A) load inertia
(B) rotor inertia
(C) both rotor and load inertia
(D) none of the above
Ans: C
Q.49 Oil-filled cable has a working stress of _ kV/mm
(A) 10
(B) 12
(C) 13
(D) 15
Ans: D
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.50 Inverse definite minimum time lag relay is also called
(A) pilot relay.
(B) differential relay.
(C) over current relay.
(D) directional overcurrent relay.
Ans: B
Q.51 Specific heat of nickel –chrome is _
(A) 0.112
(B) 0.106.
(C) 0.108.
(D) 0.110.
Ans: None of these
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.54 The speed-torque characteristics of a DC series motor are approximately similar to those of the _motor.
(A) universal
(B) synchronous
(C) DC shunt
(D) two-phase
Ans: A
Q. 55 The rotor frequency for a 3 phase 1000 RPM 6 pole induction motor with a slip of 0.04 is _Hz
(A) 8
(B) 4
(C) 6
(D) 2
Ans: D
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.56 The torque-speed characteristics of an a.c. operated universal motor has a characteristic and it be started under no-load condition.
(A) inverse, can
(B) nearly inverse, can
(C) inverse, cannot
(D) nearly inverse, cannot
Ans: C
Q.57 In the heating process of the type a simple method of temperature control is possible by means of a special alloy which loses its magnetic properties at a particular high temperature and regains them when cooled to a temperature below this value.
(A) Indirect induction over
(B) core type induction furnace
(C) coreless induction furnace
(D) high frequency eddy current
Ans: D
Q.58 In order to reduce the harmful effects of harmonics on the A.C. side of a high voltage D.C. transmission system _ are provided.
(A) synchronous condensers
(B) shunt capacitors
(C) shunt filters
(D) static compensators
Ans: C
Q.59 An a.c. tachometer is just a with one phase excited from the carrier frequency.
(A) two-phase A.C. servomotor
(B) two-phase induction motor
(C) A.C. operated universal motor
(D) hybrid stepper motor.
Ans: D
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.60 The torque, in a is proportional to the square of the armature current
(A) DC shunt motor
(B) stepper motor
(C) 2-phase servomotor
(D) DC series motor
Ans: D
Q.61 The synchronous speed for a 3 phase 6-pole induction motor is 1200 rpm. If the number of poles is now
reduced to 4 with the frequency remaining constant, the rotor speed with a slip of 5% will be .
(A) 1690 rpm
(B) 1750 rpm
(C) 1500 rpm
(D) 1710 rpm
Ans: D
Q.62 The eddy current loss in an a-c electric motor is 100 watts at 50 Hz. Its loss at 100 Hz will be
(A) 25 watts
(B) 59 watts
(C) 100 watts
(D) 400 watts
Ans: D
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.63 The maximum power for a given excitation in a synchronous motor is developed when the power angle is equal to
(A) 0o
(B) 45o
(C) 60o
(D) 90o
Ans: A
Q.64 A commutator in a d.c. machine
(A) Reduces power loss in armature.
(B) Reduces power loss in field circuit.
(C) Converts the induced a.c armature voltage into direct voltage.
(D) Is not necessary.
Ans: C
Q.65 The speed of a d.c. shunt motor at no-load is
(A) 5 to 10%
(B) 15 to 20%
(C) 25 to 30%
(D) 35 to 40% higher than its speed at rated load.
Ans: A
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.66 The efficiency of a transformer is mainly dependent on
(A) core losses.
(B) copper losses.
(C) stray losses.
(D) dielectric losses.
Ans: A
Q.67 When two transformers are operating in parallel, they will share the load a under:
(A) proportional to their impedances.
(B) inversely proportional to their impedances.
(C) 50% – 50%
(D) 25%-75%
Ans: A
Q.69 A 3-phase, 400 votts, 50 Hz, 100 KW, 4 pole squirrel cage induction motor with a rated slip of 2% will have a rotor speed of
(A) 1500 rpm
(B) 1470 rpm
(C) 1530 rpm
(D) 1570 rpm
Ans: B
Q.71 The voltage at the two ends of a transmission line are 132 KV and its reactance is 40 ohm. The Capacity of
the line is
(A) 435.6 MW
(B) 217.8 MW
(C) 251.5 MW
(D) 500 MW
Ans: A
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.72 A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary winding open circuited. Then
(A) Both eddy current and hysteresis losses decreases.
(B) Both eddy current and hysteresis losses increases.
(C) Eddy current loss remains the same but hysteresis loss increases.
(D) Eddy current loss increases but hysteresis loss remains the same.
Ans: A
Q.73 A synchronous motor is operating on no-load at unity power factor. If the field current is increased, power factor will become
(A) Leading & current will decrease
(B) Lagging & current will increase.
(C) Lagging & current will decrease.
(D) Leading & current will increase.
Ans: A
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.74 A d.c. shunt motor runs at no load speed of 1140 r.p.m. At full load, armature reaction weakens the main flux by 5% whereas the armature circuit voltage drops by 10%. The motor full load speed in r.p.m. is
(A) 1080
(B) 1203
(C) 1000
(D) 1200
Ans: A
Q.75 The introduction of interpoles in between the main pole improves the performance of d.c. machines, because
(A) The interpole produces additional flux to augment the developed torque.
(B) The flux waveform is improved with reduction in harmonics.
(C) The inequality of air flux on the top and bottom halves of armature is removed.
(D) A counter e.m.f. is induced in the coil undergoing commutation.
Ans: D
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.76 The rotor power output of a 3-phase induction motor is 15 KW and corresponding slip is 4%.The rotor copper loss will be
(A) 600 W.
(B) 625 W
(C) 650 W
(D) 700 W
Ans: B
Q.77 The direction of rotation of hysteresis motor is reversed by
(A) Shift shaded pole with respect to main pole
(B) Reversing supply lead
(C) Either A or B
(D) Neither A nor B
Ans: A
Q.78 A 1.8°step, 4-phase stepper motor has a total of 40 teeth on 8 pole of stator. The number of rotor teeth for their rotor will be
(A) 40
(C) 100
(B) 50
(D) 80
Ans: B
Q.79 Low head plants generally use
(A) Pelton Turbines
(B) Francis Turbine
(C) Pelton or Francis Turbine
(D) Kaplan Turbines
Ans: A
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.80 The charging reactance of 50 Km length of line is 1500fi. The charging reactance for 100Km length of line will be
(A) 1500 fi
(B) 3000 fi
(C) 750 fi
(D) 600 fi
Ans: B
Q.81 Electric ovens using heating elements of can produce temperature upto 3000°C.
(A) Nickel
(B) Graphite
(C) Chromium
(D) Iron
Ans: C
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.82 In DC generators, armature reaction is produced actually by
(A) Its field current.
(B) Armature conductors.
(C) Field pole winding.
(D) Load current in armature.
Ans: D
Q.83 Two transformers operating in parallel will share the load depending upon their
(A) Rating.
(B) Leakage reactance.
(C) Efficiency.
(D) Per-unit impedance.
Ans: A
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.84 As compared to shunt and compound DC motors, the series DC motor will have the highest torque because of its comparatively at the start.
(A) Lower armature resistance.
(B) Stronger series field.
(C) Fewer series turns.
(D) Larger armature current.
Ans: D
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.85 A 400kW, 3-phase, 440V, 50Hz induction motor has a speed of 950 r.p.m. on full- load. The machine has 6 poles. The slip of the machine will be.
(A) 0.06
(B) 0.10
(C) 0.04
(D) 0.05
Ans: D
Q.86 Reduction in the capacitance of a capacitor-start motor, results in reduced
(A) Noise.
(B) Speed.
(C) Starting torque.
(D) Armature reaction.
Ans: C
Q.87 Regenerative braking
(A) Can be used for stopping a motor.
(B) Cannot be easily applied to DC series motors.
(C) Can be easily applied to DC shunt motors
(D) Cannot be used when motor load has overhauling characteristics.
Ans: B
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.88 At present level of technology, which of the following method of generating electric power from sea is most advantageous?
(A) Tidal power.
(B) Ocean thermal energy conversion
(C) Ocean currents.
(D) Wave power.
Ans: A
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.89 If the field circuits of an unloaded salient pole synchronous motor gets suddenly open circuited, then
(A) The motor stops.
(B) It continues to run at the same speed.
(C) Its runs at the slower speed.
(D) It runs at a very high speed.
Ans: B
Q.90 Electric resistance seam welding uses electrodes.
(A) Pointed
(B) Disc.
(C) Flat
(D) Domed
Ans: B
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.91 For LV applications (below 1 kV), cables are used.
(A) Paper insulated.
(B) Plastic.
(C) Single core cables.
(D) Oil filled.
Ans: C
Q.92 No load current in a transformer:
(A) lags the applied voltage by 90°
(B) lags the applied voltage by somewhat less than 90°
(C) leads the applied voltage by 90°
(D) Leads the applied voltage by somewhat less than 90°
Ans: B
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q.95 The armature of a dc machine is laminated to reduce:
(A) Eddy current loss
(B) Hysteresis loss
(C) copper losses
(D) friction and windage losses
Ans: A
Q.97 A single phase Hysteresis motor
(A) can run at synchronous speed only
(B) can run at sub synchronous speed only
(C) can run at synchronous and super synchronous speed
(D) can run at synchronous and sub synchronous speed
Ans: A
ELECTRICAL100 IMPORTANT EXPECTED MCQ
Q. 98 The temperature of resistance furnaces can be controlled by changing the:
(A) applied voltage
(B) number of heating elements
(C) circuit configuration
(D) All of the above
Ans: D
Q.99 The line trap unit employed in carrier current relaying:
(A) offers high impedance to 50 Hz power frequency signal
(B) offers high impedance to carrier frequency signal
(C) offers low impedance to carrier frequency signal
(D) Both
(A) & (C)
Ans: B
ELECTRICAL100 IMPORTANT EXPECTED MCQ
