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

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Electrical Machines
The introduction of interpoles in between the main poles improves the performance of a dc machine, because

 the flux waveform is improved with reduction in harmonics
 the inequality of air-gap flux on the top and bottom halves of the armature is removed
 a counter-emf is induced in the coil undergoing commutation
 the interpoles produce additional flux to augment the developed torque

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