Explore topic-wise MCQs in Electrical Engineering.

This section includes 21 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.

1.

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
Answer» E.
2.

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
Answer» D. (Ns-l)s
3.

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
Answer» D. 0.2 Hz
4.

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
Answer» B. Rotor rheostat control
5.

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
Answer» C. large
6.

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
Answer» D. none of the above
7.

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
Answer» C. universal motor
8.

The complete circle diagram of induetion motor can be drawn with the help of data found from

A. noload test
B. blocked rotor test
C. stator resistance test
D. all of the above
Answer» E.
9.

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
Answer» E.
10.

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
Answer» C. Cascade operation
11.

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
Answer» E.
12.

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
Answer» E.
13.

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
Answer» B. will continue running burning its two phases
14.

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
Answer» D. cogging
15.

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
Answer» C. The rotor will run at very high speed
16.

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
Answer» C. in series-parallel
17.

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
Answer» D. reducing supply voltage
18.

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
Answer» B. Cast iron bearings
19.

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
Answer» B. reduce copper losses
20.

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
Answer» E.
21.

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.
Answer» B. 960 r.p.m.