Practice Test: Question Set - 09
1. If the terminals of armature of D.C. motor are interchanged, this action will offer following kind of braking
- (A) Regenerative
- (B) Plugging
- (C) Dynamic braking
- (D) None of the above
2. D.C. shunt motors are used for driving
- (A) Trains
- (B) Cranes
- (C) Hoists
- (D) Machine tools
3. During rheostat braking of D.C. series motors
- (A) Motor is run as a generator
- (B) Motor is reversed in direction
- (C) Motor is run at reduced speed
- (D) None of these
4. Which D.C. motor is preferred for elevators?
- (A) Shunt motor
- (B) Series motor
- (C) Differential compound motor
- (D) Cumulative compound motor
5. In case of D.C. shunt motors the speed is dependent on back e.m.f. only because
- (A) Back e.m.f. is equal to armature drop
- (B) Armature drop is negligible
- (C) Flux is proportional to armature current
- (D) Flux is practically constant in D.C. shunt motors
6. The current drawn by the armature of D.C. motor is directly proportional to
- (A) The torque required
- (B) The speed of the motor
- (C) The voltage across the terminals
- (D) None of the above
7. Sparking, is discouraged in a D.C. motor because
- (A) It increases the input power consumption
- (B) Commutator gets damaged
- (C) Both (A) and (B)
- (D) None of the above
8. Which motor has the poorest speed control?
- (A) Differentially compounded motor
- (B) Cumulatively compounded motor
- (C) Shunt motor
- (D) Series motor
9. In a D.C. generator all of the following could be the effects of iron losses except
- (A) Loss of efficiency
- (B) Excessive heating of core
- (C) Increase in terminal voltage
- (D) Rise in temperature of ventilating air
10. By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?
- (A) Frame
- (B) Shaft
- (C) Commutator
- (D) Stator
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