Electrical Machines
A transformer has resistance and reactance in per unit as 0.01 and 0.04 respectively. Its voltage regulation for 0.8 power factor lagging and leading will be

None of these
 6% and -4%
 3.2% and -1.6%
 4.8% and -3.2%

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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

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

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