Electrical Machines
If the excitation of the synchronous generator fails, it acts as a/an

 synchronous generator.
  induction generator.
 synchronous motor.
 induction motor.

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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
Commutation in a DC machine may be explained as a process

 how alternate flux affects the main field flux.
  in which magnetic field is set up.
  by which electric current in a coil is reversed.
 by virtue of which emf is induced in the armature conductors.

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