Electrical Machines
The mmf produced by rotor currents of a 3 - Φ induction motor

  rotates at slip speed with respect to stator mmf.
  rotates at the speed of rotor in the air gap.
  rotates at synchronous speed with respect to rotor.
  is at standstill with respect to stator mmf.

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
In case of 3 - Φ IM, plugging means

  interchanging two supply phases for quick stopping.
  locking of rotor due to harmonics.
  pulling the motor directly on line without a rotor.
  starting the motor on load which is more than the rated load.

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
The 3 - Φ induction motors are, by a very considerable margin, the most widely used AC motors as

  these are cheaper in cost, simple and rugged in construction.
  they have very good speed regulation.
  they have maximum efficiency and maximum starting torque.
  they are capable of operation under range of leading and lagging pf.

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
If the frequency of input voltage of a transformer is increased keeping the magnitude of voltage unchanged, then

 Pe will increase but Ph will decrease
 Ph will increase but Pe will decrease
 both hysteresis loss(Ph) and eddy current loss(Pe) will increase
 Ph will decrease but Pe will remain same

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
With the increase in speed of a DC motor

 back emf falls and line current increases.
 both back emf as well as line current fall.
 both back emf as well as line current increase.
 back emf increases but line current falls.

ANSWER DOWNLOAD EXAMIANS APP