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

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

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Electrical Machines
Armature reaction in a DC machine

 makes an angle with the main pole axis which is load dependent.
 is in direct opposition to the main poles.
  makes an angle of 90° with the main pole axis.
 is in the same direction as the main poles.

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