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 magnetude of current will increase, but power factor will decrease.
 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.

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Electrical Machines
Consider the following statements regarding dc machines : 1. possible resistance of shunt-field winding is 1 Ω 2. possible resistance of series-field winding is 1 Ω 3. electrographite brushes are used for 230 V, 10 A machines 4. Copper-graphite brushes are used for 230 V, 10 A machines 5. Possible armature-circuit resistance is 1 Ω From these, the correct statements are

 1, 4
 2, 4 ,5
 1, 3, 5
 2, 3 , 5

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Electrical Machines
In a star - delta starting of an IM

  line voltage is 57.7 % of stator voltage.
  applied voltage per stator phase is 57.7 % of a line volt
  resistance is inserted in the rotor.
  reduced voltage is applied to the stator.

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