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.Management Sciences
Category: D.C. Motors
If the speed of a D.C. shunt motor is increased, the back e.m.f. of the motor will_________?
A. increase
B. decrease
C. remain same
D. become zero
If a D.C. motor designed for 40°C ambient temperature is to be used for 50°C ambient temperature, then the motor_____________?
A. of lower H.P. should be selected
B. of higher H.P. should be selected
C. can be used for 50°C ambient temperature also
D. is to be derated by a factor recommended by manufacturer and select the next higher H.P. motor
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
Which D.C. motor has got maximum self loading property?
A. Series motor
B. Shunt motor
C. Cumulatively compounded ‘motor
D. Differentially compounded motor
Ward Leonard method of speed control is basically a______________?
A. field control method
B. armature controlled method
C. field diverter
D. frequency control method
Which of the following motor is preferred for operation in highly explosive atmosphere ?
A. Series motor
B. Shunt motor
C. Air motor
D. Battery operated motor
Which method of braking is generally used in elevators ?
A. Plugging
B. Regenerative braking
C. Rheostatic braking
D. None of the above
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
For which of the following applications a D.C. motor is preferred over an A.C. motor ?
A. Low speed operation
B. High speed operation
C. Variable speed operation
D. Fixed speed operation
Why are the D.C. motors preferred for traction applications ?
A. Torque and speed are inversely proportional to armature current
B. Torque is proportional to armature current
C. Torque is proportional to square root of armature current
D. The speed is inversely proportional to the torque and the torque is proportional to square of armature current
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