D.C. Motors

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

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

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

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

These days D.C. motors are widely used in____________?

A. pumg sets
B. air compressors
C. electric traction
D. machine shops

In a D.C. shunt motor, under the conditions of maximum power, the current in the armature will be_____________?

A. almost negligible
B. rated full-load current
C. less than full-load current
D. more than full-load current

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

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

A direct on line starter is used: for starting motors___________?

A. up to 5 H.P
B. up to 10 H.P
C. up to 15 H.P
D. up to 20 H.P

In a D.C. shunt motor, speed is______________?

A. independent of armature current
B. directly proportional to the armature current
C. proportional to the square of the current
D. inversely proportional to the armature current