Electrical Machines
An ideal synchronous motor has no starting torque because

 rotor is made up of salient poles.
  relative velocity between stator and rotor mmf’s is not zero.
 rotor winding is highly reactive.
 relative velocity between the stator and rotor mmf’s is zero.

ANSWER DOWNLOAD EXAMIANS APP

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.
 it reduces field structure iron losses
 commutator action is not possible otherwise

ANSWER DOWNLOAD EXAMIANS APP