Ø QUE-ANS:

[1]        How may the direction of rotation of n dc motor be reversed?

By reversing either the field current or current through the armature. Usually, reversal of current through the armature is adopted.

[2]        What will happen if both currents are reversed?

The motor will run in the original direction’

[3]        What will happen if the field of a dc shunt motor is opened?

The motor will achieve dangerously high speed and may destroy itself.

[4]        What happens  if the direction of current at the terminals of a series motor is reversed?

It does not reverse the direction of rotation of motor because current flows through armature in the same direction as through the field.

[5]        In rewinding the armature of a DC motor, progressive connections are changed to retrogressive ones; will it affect the operation anyway?

Yes. Now the armature will rotate in the opposite direction.