D.C. Motors

One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven_______________?

A. runs as a generator
B. does not run as a generator
C. also runs as a motor comes to stop after sometime

The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by______________?

A. reducing the field current
B. decreasing the armature current
C. increasing the armature current
D. increasing the excitation current
E. none of the above methods

In the D.C. motor the iron losses occur in____________?

A. the field
B. the armature
C. the brushes
D. the commutator

Which D.C. motor has got maximum self relieving property ?

A. Series motor
B. Shunt motor
C. Cumulatively compounded motor
D. Differentially compounded motor

D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this______________?

A. series motor
B. shunt motor
C. compound motor
D. any of the above

D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the________________?

A. series motor
B. shunt motor
C. compound motor
D. any of the above

If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens____________?

A. this will make armature to take heavy current, possibly burning it
B. this will result in excessive speed, possibly destroying armature due to excessive centrifugal stresses
C. nothing will happen to motor
D. motor will come to stop

Where D.C. motor of H.P. 12 or more requires frequent starting, stopg, reversing and speed control______________?

A. drum type controller is used
B. three point starter is used
C. four point starter is used
D. all above can be used

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

In variable speed motor___________?

A. a stronger commutating field is needed at low speed than at high speed
B. a weaker commutating field is needed at low speed than at high speed
C. same commutating field is needed at low speed than at high speed
D. none of the above is correct