Electrical Machines
DC generator will not build up voltage

  if it has lost residual magnetism.
 if field resistance is more than critical resistance.
 due to wrong direction of rotation.
 any one of above.

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Electrical Machines
For a given torque, reducing divertor resistance of a DC series motor

  Decrease in speed demanding less armature current.
  Decrease in speed but armature current remains the same.
  Increase in speed demanding more armature current.
  Increase in speed but armature currnet remains the same.

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Electrical Machines
A dc shunt generator, when commissioned after a major repair of the field system, failed to build Up voltage. It was because

 field system lost residual magnetism
 field resistance was higher than critical resistance
 field winding was wrongly connected
 there was a break in the armature circuit

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