Electrical Machines
A DC series motor must started on no load because it would

 Not develop starting torque.
  Run at dangerously high speed.
 Fail to start without load.
 Draw more current without producing sufficient torque.

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Electrical Machines
Flashing the field of DC generator means

  creating residual magnetism by a DC source.
  neutralising residual magnetism.
 increasing flux density by adding extra turns of winding.
  making the magnetic losses forces parallel.

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Electrical Machines
Compensating windings are used in DC generators

  mainly to reduce the eddy currents by providing local short circuit.
  to provide path for the circulation of cooling air.
None of these
  to neutralize the cross magnetizing effect of the armature reaction.

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