Single Phase Induction Motors

11. A universal motor is one which

  1. can be operated either on D.C. or A.C. supply at approximately the same speed and output
  2. can be marketed internationally
  3. runs at dangerously high speed on no-load
  4. None of these

Correct answer: (A)
can be operated either on D.C. or A.C. supply at approximately the same speed and output

12. A.C. series motor as compared to D.C. series motor has

  1. smaller brush width
  2. less number of field turns
  3. more number of armature turns
  4. less air gap
  5. all of the above

Correct answer: (E)
all of the above

13. After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on

  1. running winding
  2. rotor winding
  3. field winding
  4. compensating winding

Correct answer: (A)
running winding

14. As hysteresis motors are free from mechanical and magnetic vibrations therefore these are considered as suitable for

  1. fans
  2. blowers
  3. sound equipment
  4. mixer grinders

Correct answer: (C)
sound equipment

15. Burning out of windings is due to

  1. short circuited capacitor
  2. capacitor value hiving changed
  3. open circuiting of capacitor
  4. none of the above

Correct answer: (A)
short circuited capacitor

16. Centrifugal switch disconnects the auxiliary winding of the motor at about _________ percent of synchronous speed

  1. 30 to 40
  2. 70 to 80
  3. 80 to 90
  4. 100

Correct answer: (B)
70 to 80

17. Direction of rotation of a split phase motor can be reversed by reversing the connection of

  1. running winding only
  2. starting winding only
  3. either (a) or (b)
  4. both (a) and (b)

Correct answer: (C)
either (a) or (b)

18. For which of the applications a reluctance motor is preferred?

  1. Electric shavers
  2. Refrigerators
  3. Signalling and timing devices
  4. Lifts and hoists

Correct answer: (C)
Signalling and timing devices

19. Hysteresis motor is particularly useful for high-quality record players and tape-recorders because

  1. it revolves synchronously
  2. it is not subject to any magnetic or mechanical vibrations
  3. it can be easily manufactured in extremely small sizes of up to 1 W output
  4. it develops hysteresis torque which is extremely steady both in amplitude and phase

Correct answer: (D)
it develops hysteresis torque which is extremely steady both in amplitude and phase

20. If a D.C. series motor is operated on A.C. supply, it will

  1. spark excessively
  2. have poor efficiency
  3. have poor power factor
  4. all of the above

Correct answer: (D)
all of the above

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