Electrical Machines
In a synchronous motor electromagnetic power varies

 directly as applied voltage
None of these
 inversely as applied voltage
 directly as square of applied voltage

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Electrical Machines
A 3-φ alternator has negligible stator resistance. A short circuit test is conducted on this alternator. At a particular speed, a field current of If1 is required to drive the rated armature current. If the speed of the alternator is reduced to half, the field current required to maintain rated armature current

 Woud be equal to 2If1.
 Would be equal to If1/2.
 Would be equal to If1.
  Cannot be predicted due to insufficient data.

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Electrical Machines
Armature reaction in a DC machine

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

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