Electrical Machines
A separately-excited DC generator, running at rated speed, has 6 volts across its armature terminals with no field current. When field winding is excited with one ampere, the voltage builds up to 250 V at no load. In case field current is reduced to zero, with the speed remaining unaltered, the armature terminal voltage would be

 more than 6 V
 6 V
 zero
 less than 6 V

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

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