Electrical Machines
In a transformer the magnetic coupling between the primary and secondary winding can be increased by

 using the magnetic core of low reluctance.
 using soft material for winding.
 increasing the number of turns.
 using transformer oil of better quality.

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

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