Electrical Machines
A 500 V, 55 kVA single phase alternator has an effective resistance of 0.5 Ω. An excitation current of 10 A produces 200 A armature current on short circuit and an emf of 450 V on per circuit. The synchronous reactance will be

 2.74 Ω.
 25.564 Ω.
  2.241 Ω.
 2.781 Ω.

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Electrical Machines
In a loaded DC generator, if the brushes are given a shift from the interpolar axis in the direction of rotation, then the commutation will

 deteriorate with fall of terminal voltage.
 deteriorate with rise in terminal voltage.
 improve with rise in terminal voltage.
 improve with fall of terminal voltage.

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

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