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MCQ of D.C motor page-10


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51. The supply terminals for a dc shunt motor reversed. What will be effect on the motor?

A) It will burn
B) It will stop
C) It will run in reverse direction
D) It will run as a dc generator

Ans : (C)

52. The retardation test in case of shunt motors and generators is used to determine

A) friction losses
B) eddy current losses
C) copper losses
D) stray losses.

Ans : (D)

53. A dc motor develops a torque of the 100 N-m at 400 rpm. At 300 rpm the motor will develop a torque of

A) 133 N-m
B) 100 N-m
C) 67 N-m
D) 180 N-m.

Ans : (B)

54. What will happen if the back e.m.f. of a dc motor suddenly vanishes

A) the motor will burn
B) the efficiency of motor will rise abruptly
C) the motor will start hunting
D) the motor will run faster than the rated value.

Ans : (A)

55. A 230 V dc shunt has armature resistance 0.5 Ω motor takes a no-load current of 2 A and runs at 1200 rpm. In cast the full load current is 40 A, the speed at full load will be

A) 1000 rpm
B) 1100 rpm
C) 1200 rpm
D) 1250 rpm.

Ans : (B)

56. A 200 V dc motor will be subjected to a high voltage test at

A) 1400 V
B) 1000 V
C) 500 V
D) 250 V.

Ans : (A)

57. Which test can be used to dc determine the no-load losses of a shunt motor ?

A) Brake test
B) Retardation test
C) Hopkinson’s test
D) Swinburne’s test.

Ans : (D)

58. Which of the following test can be used to measure stray losses?

A) Field’s test
B) Running down test
C) Swinburne’s test
D) Brake test.

Ans : (B)

59. In a dc motor which of the following can sustain the maximum temperature rise?

A) Slip rings
B) Commutator
C) Field winding
D) Armature winding.

Ans : (C) and (D)

60. In class B dc motors, the maximum permissible temperature rise in armature winding is

A) 45o C
B) 55o C
C) 75o C
D) 105o C.

Ans : (C)


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