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

 a counter-emf is induced in the coil undergoing commutation
 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
 the interpoles produce additional flux to augment the developed torque

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Electrical Machines
If two 8-pole dc machines of identical armature sare wound, one with lap winding and the other with wave winding, then

 wave-wound machine will have more rated voltage and less current
 lap-wound machine will have more rated voltage and more current
 lap-wound machine will have more rated voltage and less current
 wave-wound machine will have more rated current and more voltage

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