multiple choice questions on dc generator # 5

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multiple choice questions on dc generator 5


1) Short-circuiting is caused in the armature winding due to
A) failure of insulation between two turns of a coil.
B) failure of insulation between two commutator bars.
C) grounding of two or more turns of the same coil.
D) any of the above.

Ans:D

2) In a lap wound dc generator, the equalizer rings are provided to
A) neutralize the armature reaction effect.
B) avoid short-circuiting.
C) avoid unequal distribution of currents at brushes.
D) avoid harmonics generated in the emf.
E) provide mechanical balancing.

Ans:C

3) In a drum type dc armature winding the back pitch and front pitch in terms of the coil-sides must be
A) even and odd respectively
B) odd and even respectively
C) both even
D) both odd

Ans:D

4) In a dc machine, the actual flux distribution depends upon
A) size of air gap
B) shape of poles shoes
C) clearance between tips of the adjacent poles shoes
D) all of the above.

Ans:D

5) In dc machines, the air gap flux distribution in space at no load is
A) sinusoidal
B) triangular
C) flat topped
D) pulsating

Ans:C

6) In a dc machine, the number of mechanical and electrical degrees will be same when the number of poles on the machine is
A) 4
B) 2
C) 8
D) 1

Ans:B

7) The sparking at the brushes, in a dc machine, is due to
A) armature reaction
B) reactance voltage
C) presence of commutator
D) high resistance of carbon brushes.

Ans:B

8) The self induced emf in the coil undergoing commutation is called the
A) reactance voltage
B) statically induced voltage
C) dynamically induced voltage
D) none of the above

Ans:A

9) Compensating winding in a dc machine is placed on
A) armature in slots.
B) yoke in the interpolar gap
C) yoke in the pole faces
D) partly in armature slots and partly in poles faces.

Ans:C

10) The Compensating winding in a dc machine
A) is located in armature slots for compensation of the armature reaction.
B) is located on commutating poles for improving commutation
C) is located on poles shoes for avoiding the flash over at the commutator surface.
D) is located on poles shoes to avoid the sparking at the brushes.

Ans:C

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