Electrical Machines
Counter emf of a DC motor

 regulates its armature voltage.
 helps in energy conversion.
 aids applied voltage.
 exceeds supply voltage

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Electrical Machines
Two of supply terminals to a 3 - Φ induction motor get interchanged during re-connection after normal maintenance. When switched on the supply, the motor will

  rotate in the same direction as before maintenance.
  rotate in direction opposite to that before maintenance.
  not start at all.
  get heated and damaged.

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Electrical Machines
Cogging in induction motor occurs when

 number of stator teeth - number of rotor teeth = odd number.
 number of stator teeth - number of rotor teeth = 0.
 number of stator teeth - number of rotor teeth = even number.
 number of stator teeth - number of rotor teeth = negative number.

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