Electrical Machines
What is the necessity of copper brushes in a dc motors?

  To absorb the mechanical shocks produced during running condition.
  To increase the flux cutting by the rotor.
  None of these.
  To convert alternating supply current to direct current.

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
In a loaded DC generator, if the brushes are given a shift from the interpolar axis in the direction of rotation, then the commutation will

 deteriorate with fall of terminal voltage.
 improve with rise in terminal voltage.
 improve with fall of terminal voltage.
 deteriorate with rise in terminal voltage.

ANSWER DOWNLOAD EXAMIANS APP