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single phase induction motors MCQs

Practise focused single phase induction motors questions with marked answers for exam preparation and subject revision.

single phase induction motors Mcqs
1. 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___________?
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A. at the slot edge where coil enters or comes out of the slot

B. at the end connections

C. at the end terminals

D. anywhere on the winding inside a slot

2. Which of the following motor will give the highest starting torque ?
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A. D.C. shunt motor

B. Repulsion start and induction run motor

C. Universal motor

D. Schrage motor
3. The power factor of a single-phase induction motor is usually?
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A. always leading

B. lagging

C. unity

D. unity to 0.8 leading

4. Which of the following motors is used in a situation where load increases with speed ?
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A. Hysteresis motor

B. Induction motor

C. Three-phase series motor

D. Schrage motor

5. In split phase motor main winding is of _____________?
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A. thin 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. thick wire placed at the bottom of the slots
6. A schrage motor can run on___________?
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A. positive slip

B. zero slip

C. all of the above

D. negative slip

7. A centrifugal switch is used to dis- connect starting winding when motor has___________?
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A. picked up about 50 to 70 per cent of rated speed

B. run for about 1 minute

C. picked up about 10 to 25 per cent of rated speed

D. run for about 5 minutes

8. After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on ______________?
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A. running winding

B. compensating winding

C. field winding

D. rotor winding

9. The range of efficiency for shaded pole motors is______________?
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A. 80% to 90%

B. 5% to 35%

C. 95% to 99%

D. 50% to 75%

10. A single-phase induction motor is__________?
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A. inherently non-self-starting with low torque

B. inherently self-starting with low torque

C. inherently non-self-starting with high torque

D. inherently self-starting with high torque

11. In a single phase motor the centrifugal switch____________?
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A. reconnects the auxiliary winding of the motor

B. disconnects auxiliary winding of the motor

C. reconnects the main winding the motor

D. disconnects main winding of the motor

12. In a split phase motor____________?
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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

13. Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a___________?
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A. thermal relay

B. none of the above

C. centrifugal switch

D. magnetic relay
14. If the capacitor of a single-phase motor is short-circuited_________?
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A. the motor will not start

B. the motor will run in reverse direction

C. the motor will run in the same direction at reduced r.p.m

D. the motor will run

15. Hysteresis motor is particularly useful for high-quality record players and tape-recorders because___________?
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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
16. If starting winding of a single-phase induction motor is left in the circuit, it will____________?
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A. spark at light loads

B. run faster

C. run slower

D. draw excessive current and overheat
17. The direction of rotation of universal motor can be reversed the by reversing the flow of current through__________?
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A. none of the above

B. field winding

C. armature winding

D. either armature winding or field winding
18. Which of the following statements regarding repulsion-start induction motor is incorrect ?
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A. In fractional horse power motors, it has replaced the capacitor motors

B. It is not easily reversed

C. It requires more maintenance of commutator and other mechanical devices

D. It makes quite a bit of noise on starting

19. The speed of a universal motor is generally reduced by using_________?
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A. gear trains

B. V-belts

C. chains

D. brakes

20. In repulsion motor, maximum torque is developed when____________?
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A. none of the above

B. brush axis coincides with the field axis

C. brush axis is at 90 electrical to the field axis

D. brush axis is at 45 electrical to the field axis