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

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

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Electrical Machines
With the increase in speed of DC motor

  Back emf increase but line current falls.
 Both back emf as well as line current fall.
 Back emf falls and line current increase.
 Both back emf as well as line current increase.

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