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MCQ of D.C motor page-5


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1. The fully load current of a 20 HP 500 V dc motor will be closer to

A) 15 A
B) 35 A
C) 60 A
D) 100 A.

Ans : (B)

2. The speed of a series wound dc motor

A) cannot be controlled by diverter
B) can be controlled by shunt field regulator
C) increases as armature circuit resistance increases
D) increases as flux decreases.

Ans : (D)

3. An electric motor may give noise due to

A) cooling air
B) defective bearing
C) magnetic effect
D) all of the above.

Ans : (D)

4. A dc motor having full load speed of 800 and speed regulation of 8% will have no load speed of

A) 736 rpm
B) 768 rpm
C) 864 rpm
D) 832 rpm.

Ans : (C)

5. If conditions for maximum power for a dc motor are established, the efficiency of the motor will be

A) 100%
B) 90 to 95%
C) 81%
D) Less than 50%.

Ans : (D)

6. The speed of a dc motor is

A) always constant
B) directly proportional to back e.m.f.
C) directly proportional to flux
D) inversely proportional to the product of back e.m.f. and flux.

Ans : (B)

7. The ratio of starting torque to fully load torque is least in case of

A) shunt motors
B) series motors
C) compound motors
D) none.

Ans : (A)

8. In a dc series motor, shaft torque is less than the armature torque due to

A) stray losses
B) eddy current losses
C) hysteresis losses
D) all of the above.

Ans : (A)

9. Dc motor with self-loading properties is

A) shunt motor
B) series motor
C) differentially compound motor
D) cumulatively compound motor.

Ans : (C)

10. Which motor will have least percentage increases of input current for the same percentage increases in torque?

A) shunt motor
B) series motor
C) separately excited motor
D) cumulatively compound motors.

Ans : (B)


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