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

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

ANSWER DOWNLOAD EXAMIANS APP

Electrical Machines
Flashing of DC generator means

None of these
  increasing flux density by providing extra ampere-turns in field.
  creation of residual magnetism by a DC source.
 neutralization of residual magnetism.

ANSWER DOWNLOAD EXAMIANS APP