1. The main function of a commutator in dc motor is to
a) prevent sparking
b) convert ac to dc
c) reduce friction
d) convert dc to ac
ans. b
2. Which of the following statements is incorrect? If a starter is not used with large dc motor. It will draw a starting current which
a) is many times its full-load current
b) will produce excessive line voltage
c) will damage the commutator
d) will produce very low starting torque
ans. d
3. The factor which voltage does not cause decrease in the terminal voltage of a shunt generator is
a) armature resistance
b) armature reaction
c) reduction in field current
d) armature reactance
ans. d
4. A dc generator can be termed as
a) rotating amplifier.
b) prime mover.
c) power pump.
d) none of these
ans. a
5. The function of compensating windings placed in slots in the pole shoes is
a) to neutralize cross magnetizing effect
b) to neutralize the demagnetizing effect
c) to neutralize both the effects
d) to avoid flash over around the commutator
ans. d
6. In case of parallel operation of compound generators , for proper division of load from no load to full load , it is essential that
a) the regulation of each armature should be same
b) their series field resistances should be equal
c) their ratings should be identical
d) none of these
ans. a
7. The simplest way to shift load from one shunt generator to the other generator running in parallel is to
a) adjust their field rheostats.
b) use equalizer connection.
c) add resistance in their armature circuit
d) none of these.
ans. a
8. For parallel operation , the polarities of two generators
a) must oppose each other
b) must be same
c) may or may not be same
d) none of these
ans. a
9. The parts of the armature electric circuit which take active part in emf generation are
a) The coil sides inside the slots
b) the overhangs
c) both the coil sides inside the slots and the overhangs
d) the commutator segments
ans. a
10. The emf induced in the armature of a dc machine is
a) directly proportional to the flux and inversely proportional to the speed .
b) directly proportional to both the flux and speed.
c) inversely proportional to both the flux and the speed.
d) none of the above
ans. b
a) prevent sparking
b) convert ac to dc
c) reduce friction
d) convert dc to ac
ans. b
2. Which of the following statements is incorrect? If a starter is not used with large dc motor. It will draw a starting current which
a) is many times its full-load current
b) will produce excessive line voltage
c) will damage the commutator
d) will produce very low starting torque
ans. d
3. The factor which voltage does not cause decrease in the terminal voltage of a shunt generator is
a) armature resistance
b) armature reaction
c) reduction in field current
d) armature reactance
ans. d
4. A dc generator can be termed as
a) rotating amplifier.
b) prime mover.
c) power pump.
d) none of these
ans. a
5. The function of compensating windings placed in slots in the pole shoes is
a) to neutralize cross magnetizing effect
b) to neutralize the demagnetizing effect
c) to neutralize both the effects
d) to avoid flash over around the commutator
ans. d
6. In case of parallel operation of compound generators , for proper division of load from no load to full load , it is essential that
a) the regulation of each armature should be same
b) their series field resistances should be equal
c) their ratings should be identical
d) none of these
ans. a
7. The simplest way to shift load from one shunt generator to the other generator running in parallel is to
a) adjust their field rheostats.
b) use equalizer connection.
c) add resistance in their armature circuit
d) none of these.
ans. a
8. For parallel operation , the polarities of two generators
a) must oppose each other
b) must be same
c) may or may not be same
d) none of these
ans. a
9. The parts of the armature electric circuit which take active part in emf generation are
a) The coil sides inside the slots
b) the overhangs
c) both the coil sides inside the slots and the overhangs
d) the commutator segments
ans. a
10. The emf induced in the armature of a dc machine is
a) directly proportional to the flux and inversely proportional to the speed .
b) directly proportional to both the flux and speed.
c) inversely proportional to both the flux and the speed.
d) none of the above
ans. b
