Electrical Machines
A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ω. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is

 1.06
 0.87
 0.95
 0.96

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Electrical Machines
Armature reaction in a DC machine

 is in the same direction as the main poles.
 is in direct opposition to the main poles.
  makes an angle of 90° with the main pole axis.
 makes an angle with the main pole axis which is load dependent.

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

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