Electrical Machines
Interpoles in a DC motor must be

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

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Electrical Machines
For a given torque, reducing divertor resistance of a DC series motor

  Decrease in speed demanding less armature current.
  Decrease in speed but armature current remains the same.
  Increase in speed demanding more armature current.
  Increase in speed but armature currnet remains the same.

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