Electrical Machines
In dc machines, the armature windings are placed on the rotor because of the necessity for

 generation of voltage
 commutation
 development of torque
 electromechanical energy conversion

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Electrical Machines
Cogging in induction motor occurs when

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

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Electrical Machines
Skewing of the rotor in a 3 - Φ squirrel cage induction motor reduces

  noise and pullout torque, but increase parasitic and starting torque.
  noise, parasitic torque, starting torque and pull out torque.
  noise and parasitic torque, but increase starting and pull-out torque.
  noise, parasitic and starting torque, but increase pull out torque.

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