Electrical Machines
If the frequency of input voltage of a transformer is increased keeping the magnitude of voltage unchanged, then

 Pe will increase but Ph will decrease
 Ph will decrease but Pe will remain same
 Ph will increase but Pe will decrease
 both hysteresis loss(Ph) and eddy current loss(Pe) will increase

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

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

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