Electrical Machines
If iron loss and full load copper loss of any transformer are denoted by Pi and Pc, then the load corresponding to maximum efficiency is given by

 (Pi / Pc)2 × full Load.
 (Pi / Pc) × full Load.
  (Pi / Pc)0.5 × Full Load.
 (Pi / Pc)1.6 × full Load.

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Electrical Machines
Which of the following is done in speed control of DC motor by field flux control?

 Inserting an additional resistance in the field circuit.
 Inserting an additional resistance in the armature circuit.
 Inserting resistance to armature circuit and field circuit.
 Any of above.

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Electrical Machines
Short circuit test is performed on a transformer with a certain impressed voltage at rated frequency. If the short circuit test is now performed with the same magnitude of impressed voltage, but at frequency higher than the rated frequency then

 The magnitude will both increase.
 The magnitude of circuit as well as the power factor will decrease.
 The magnitude of current will decrease but the power factor will increase.
 The magnetude of current will increase, but power factor will decrease.

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