Electrical Machines
An IM cannot run at synchronous speed because

  induction motor will become synchronous motor.
  none of above.
  air friction will prevent it.
  rotor torque will not be produced.

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
Flashing the field of DC generator means

 increasing flux density by adding extra turns of winding.
  making the magnetic losses forces parallel.
  creating residual magnetism by a DC source.
  neutralising residual magnetism.

ANSWER DOWNLOAD EXAMIANS APP