A. shunt
B. series
C. differentially compounded
D. cumulativelyc’ompounded
D.C. Motors
Torque developed by a D.C. motor depends upon_____________?
A. magnetic field
B. active length of the conductor
C. current flow through the conductors
D. number of conductors
E. radius of armature
F. all above factors
What will happen if the back e.m.f. of a D.C. motor vanishes suddenly?
A. The motor will stop
B. The motor will continue to run
C. The armature may burn
D. The motor will run noisy
Which D.C. motor will be preferred for machine tools ?
A. Series motor
B. Shunt motor
C. Cumulative compound motor
D. Differential compound motor
Which of the following steps is likely to result in reduction of hysteresis loss in a D.C. generator ?
A. Providing laminations in armature core
B. Providing laminations in stator
C. Using non-magnetic material for frame
D. Using material of low hysteresis co-efficient for armature core material
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
When the armature of a D.C. motor rotates, e.m.f. induced is___________?
A. self-induced e.m.f.
B. mutually induced e.m.f.
C. back e.m.f
D. none of the above
A D.C. series motor is that which______________?
A. has its field winding consisting of thick wire and less turns
B. has a poor torque
C. can be started easily without load
D. has almost constant speed
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
