Electrical Machines
When applied rated voltage per phase is reduce to one half, the starting torque of three phase squirrel cage induction motor becomes

 twice the initial value
 4 time the initial value
 1/4 of the intial value
 1/2 of the initial value

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

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