Which of the following motors will be used in electric clocks?

A. D.c. shunt motor
B. D.c. series motor
C. A.c. induction motor
D. A.c. synchronous motor

Power factor of a synchronous motor is unity when_____________?

A. The armature current is maximum
B. The armature current is minimum
C. The armature current is zero
D. None of the above

Which of the following methods is used to start a synchronous motor?

A. Damper winding
B. Star-delta starter
C. Damper winding in conjunction with star-delta starter
D. Resistance starter in the armature circuit

In a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately

A. One-third
B. Twice
C. Thrice
D. Six times

A synchronous machine with large air gap has______________?

A. A higher value of stability limit
B. A small value of inherent regulation
C. A higher synchronizing power which makes the machine less sensitive to load variations
D. All of the above

To limit the operating temperature an electrical machine should have proper____________?

A. Voltage rating
B. Current rating
C. Power factor
D. Speed

When the voltage applied to a synchronous motor is increased, which of the following will reduce?

A. Stator flux
B. Pull in torque
C. Both a. and (b)
D. None of the above

An over excited synchronous motor is used for____________?

A. Fluctuating loads
B. Variable speed loads
C. Low torque loads
D. Power factor corrections

Slip rings are usually made of__________?

A. Carbon or graphite
B. Brass or steel
C. Silver or gold
D. Copper or aluminium

A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because?

A. Synchronous motor has no slip
B. Stator supply is not required to produce magnetic field
C. Mechanical load on the rotor remains constant
D. Synchronous motor has large airgap