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DC Motor MCQ Questions And Answers

D.C Motor: [ ISRO,DRDO,DMRC,SAIL, ODNANCE, HAL, WBSEDCL, RAILWAY & Others competitive] DC Motor MCQ Questions And Answers

61. The armature voltage control of D.C. motor provides

(a) constant torque drive

(b) constant voltage drive

(c) constant current drive

(d) none of the above

Ans: a

62. As there is no back e.m.f. at the instant of starting a D.C. motor, in order to prevent a heavy current from flowing though the armature circuits

(a) a resistance is connected in series with armature

(b) a resistance is connected parallel to the armature

(c) armature is temporarily open circuited

(d) a high value resistor is connected across the field winding

Ans: a

63. The speed of a D.C. shunt motor can be increased by

(a) increasing the resistance in armature circuit

(b) increasing the resistance in field circuit

(c) reducing the resistance in the field circuit

(d) reducing the resistance in the armature circuit

Ans: b

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64. Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator?

(a) Providing laminations in armature core

(b) Providing laminations in stator

(c) Using non-magnetic material for frame

(d) Using material of low hysteresis co-efficient for armature core material

Ans: d

65. In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will

(a) remain unchanged

(b) reduce to one-fourth value

(c) increase four folds

(d) be doubled

Ans: a

66. At the instant of starting when a D.C. motor is put on supply, it behaves like

(a) a highly resistive circuit

(6) a low resistance circuits

(c) a capacitive circuit

(d) none of the above

Ans: b

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68. The speed of a D.C. motor can be varied by varying

(a) field current

(b) applied voltage

(c) resistance in series with armature

(d) any of the above

Ans: d

69. Which one of the following is not necessarily the advantage of D.C. motors over A.C. motors?

(a) Low cost

(b) Wide speed range

(c) Stability

(d) High starting torque.

Ans: a

70. For a D.C. shunt motor if the excitation is changed

(a) torque will remain constant

(b) torque will change but power will remain constant

(c) torque and power both will change

(d) torque, power and speed, all will change

Ans: b

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