Electrical Machines
In dc machines, the field system has to be provided on stator unlike synchronous machines Where in it could be on any member, because

 dc machines are comparatively low rating machines.
 it reduces field structure iron losses
 commutator action is not possible otherwise
 it gives more uniform air-gap flux distribution

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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 current and more voltage
 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

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