Electrical Machines
A synchronous motor will deliver maximum power when

  input power factor is unity.
  load angle is equal to internal angle θ.
  load angle is 0°.
  load angle is 45°.

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Electrical Machines
Armature reaction in a DC machine

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

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