1) In a dc motor, energy conversion would not have been possible but for
A) input energy from the supply
B) production of back emf in the armature
C) use of commutator
D) rotation of the machine
Ans:B
2) If the back emf in a dc motor vanishes suddenly, the motor will
A) start hunting
B) burn
C) run at very high speed
D) run at very slow speed
Ans:B
3) The output indicated on the name plate of any motor is always the
A) gross power
B) power drawn in KVA
C) power drawn in KW
D) output power at the shaft
Ans:D
4) The direction of rotation of a dc shunt motor can be reversed by interchanging
A) the supply terminals
B) the field terminals only
C) the armature terminals only
D) either field or armature terminals
Ans:D
5) When the supply terminals of a dc shunt motor are interchanged
A) the motor will stop
B) the motor will run at its normal speed in the same direction as before
C) the direction of rotation will reverse
D) the motor will run much faster in the same direction
Ans:B
6) The dc compound motors are generally
A) level compound
B) cumulatively compound
C) differential compound
D) none of these
Ans:B
7) In the block diagram of a separately excited dc motor, how does the armature induced emf appear as?
A) positive feedback
B) negative feedback
C) Disturbance input
D) output
Ans:B
8) If the flux of a dc motor approaches zero, its speed will
A) approach infinity
B) approach zero
C) remain unchanged
D) between zero and infinity
Ans:A
9) The current drawn by a 220 V dc motor of armature resistance 0.5Ω and back emf 200 V is
A) 40 A
B) 44 A
C) 400 A
D) 440 A
Ans:A
10) With the increase in speed of a dc motor
A) both back emf as well as line current increase
B) both back emf as well as line current fall
C) back emf increases but line current falls
D) back emf falls and line current increases
Ans:C
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