Electrical Machines
Two dc machines A and B, using the same conductor material, have armature circuit resistances of 0.4 Ω and 1.2 Ω respectively. Of the two machines,

 A is bigger than B for the same current rating
 A is bigger than B for the same voltage rating
 both are of the same size for the same current rating
 B is bigger than A for the same current rating

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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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