Electrical Machines
If an additional resistance is connected in series with a DC motor operating at rated speed, the speed of the motor will

  Remain unaltered.
  Oscillate around the normal speed.
  Increase.
  Reduce.

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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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Electrical Machines
Consider the following statements : Interpoles in dc machines 1. reducearmature reaction effects in the interpolar region 2. have the same dimension as main polls 3. have their windings connected in series with the armature 4. have same number of turns as the armature 5. have the polarity same as that of the main pole ahead in a motor From these, the correct statements are

 1, 2, 3 and 5
 1, 2 and 3
 1, 3 and 5
 1 and 3

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Electrical Machines
An inverted V curve of synchronous motor shows variation of

 power factor and supply voltage during hunting.
 supply voltage and field current at constant excitation.
  power factor and DC excitation at constant load.
 supply voltage and excitation current at constant load.

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