Electrical Machines MCQ Questions and Answers for Practice

1. The power factor of the induction motor will be __________ if the magnetizing current is __________

1. Low ....... high
2. Low......low
3. High........high
4. High.....low

2. The magnetizing current of an induction motor will be __________ for __________ air gap

1. Smaller...........smaller
2. Larger .......... smaller
3. Larger ......... larger
4. Smaller....... larger

3. In induction motors, small air gap __________ power factor and __________ noise level

1. Increases..........also increases
2. Increases .......... reduces
3. Reduces .......... increases
4. Reduces..........also reduces

4. In induction motors, the difference between the number of stator and rotor slots should not be

1. Any of the above
2. P
3. 2P
4. 5P

5. Induction motor which of the following depends on the leakage reactance?

1. All of the above
2. Starting torque
3. Maximum torque
4. Starting current

6. The use of double squirrel cage winding on the rotor provides

1. Higher efficiency
2. Low noise
3. Reduced starting torque
4. A large starting torque

7. In induction motor if the number of rotor slots is equal to the stator slots then

1. The motor may refuse to start
2. The motor will run smoothly
3. The motor will mil at zero slip
4. The noise level will be low

8. In squirrel cage motors, skin effect occurs in

1. None of the above
2. Stator winding
3. Rotor winding
4. Both (A) and (B) above

9. A synchronous machine having large length of the air gap will have

1. Higher value of inherent regulation
2. Higher noise level
3. Smaller unbalanced magnetic pull
4. Lower limit of stability

10. Damper windings are provided in synchronous machines to

1. All of the above
2. Damp out rotor oscillations
3. Reduce the over-voltages under abnormal conditions
4. Facilitate starting

11. Which of the following motors has a high starting torque?

1. Synchronous motor
2. AC series motor
3. DC series motor
4. Induction motor

12. The starting winding of a single-phase motor is placed in

1. Field
2. Rotor
3. Stator
4. Armature

13. In a DC series motor increase in load current results in

1. Increase in the back emf
2. Decrease in speed
3. Increase in speed
4. Better commutation

14. Which DC motors has approximately constant speed?

1. All of the above.
2. Series motor
3. Shunt motor
4. Cumulatively compound motor

15. An electric machine will have high efficiency when

1. losses are low
2. input/output ratio is low
3. Reactive power is more
4. kWh consumption is low