Electrical Machines
In a 3-phase induction motor, if the supply voltage and frequency are reduced by the same ratio, then slip at which maximum torque occurs is

 more and maximum torque decreases
 more and maximum torque remains constant
 less and maximum torque increases
 less and maximum torque decreases

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

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