Electrical Machines
If the excitation is critical, the power factor of the alternator is

None of these
 lagging power factor.
 leading power factor.
 unity power factor.

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

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