Electrical Machines
A dc shunt generator, when driven without any excitation, showed an open circuit voltage of 12 V. When the field winding was excited, the voltage dropped to zero. It happened because

 field winding was wrongly connected
 there was a break in the armature circuit
 field resistance was higher than critical resistance
 there was no residual magnetism in the field circuit

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Electrical Machines
The synchronous motor can be started by

  providing damper winding in its rotor circuit.
  any of the above methods.
  coupling it with a DC compound motor.
  coupling it with a small AC induction motor called the pony motor.

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Electrical Machines
In synchronous generator, inverted V curve is drawn between

 field current on Y-axis and power factor on X-axis
 field current on X-axis and armature current on Y-axis
 field current on X-axis and power factor on Y-axis
 field current on Y-axis and armature current on X-axis

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Electrical Machines
With the increase in speed of a DC motor

 back emf increases but line current falls.
 both back emf as well as line current increase.
 back emf falls and line current increases.
 both back emf as well as line current fall.

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