711. 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
712. In which of the following applications D.C. series motor is invariably tried?
A. Starter for a car
B. Drive for a water pump
C. Fan motor
D. Motor operation in A.C. or D.C
713. In D.C. machines fractional pitch winding is used__________?
A. to improve cooling
B. to reduce copper losses
C. to increase the generated e.m.f.
D. to reduce the sparking
714. A three point starter is considered suitable for______________?
A. shunt motors
B. shunt as well as compound motors
C. shunt, compound and series motors
D. all D.C. motors
715. In case-the conditions for maximum power for a D.C. motor are established, the efficiency of the motor will be______________?
A. 100%
B. around 90%
C. anywhere between 75% and 90%
D. less than 50%
716. The ratio of starting torque to full-load torque is least in case of____________?
A. series motors
B. shunt motors
C. compound motors
D. none of the above
717. In D.C. motor which of the following can sustain the maximum temperature rise?
A. Slip rings
B. Commutator
C. Field winding
D. Armature winding
718. Which of the following law/rule can he used to determine the direction of rotation of D.C. motor ?
A. Lenz’s law
B. Faraday’s law
C. Coloumb’s law
D. Fleming’s left-hand rule
719. Which of the following load normally needs starting torque more than the rated torque?
A. Blowers
B. Conveyors
C. Air compressors
D. Centrifugal pumps
720. The starting resistance of a D.C. motor is generally_______________?
A. low
B. around 500 Q
C. 1000 Q
D. infinitely large
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