Electrical Machines
If the number of rotor slots is equal to number of stator slots, then motor refuses to start. Hence it is known as

  air gap.
  cogging.
  crawling.
  relative speed.

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Electrical Machines
The coil spam

 must be exactly equal to people pitch.
 none of above.
 can never be equal to pole pitch.
  may or may not be exactly equal to people pitch.

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Electrical Machines
Interpoles in a DC motor must be

 Shunt excited and should have the same polarity as that of the behind main pole in the direction of rotation of armature.
 Series excited and should have the same polarity as that of the ahead main pole in the direction of rotation of armature.
 Series excited and should have the same polarity as that of the behind main pole in the direction of rotation of armature.
 Shunt excited and should have the same polarity as that of the ahead main pole in the direction of rotation of armature.

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