Electrical Machines
A dc shunt generator, when commissioned after a major repair of the field system, failed to build Up voltage. It was because

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

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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
 B is bigger than A 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

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