Electrical Machines
The armature core of a DC machine is laminated to minimise

 temperature rise
 eddy-current loss
 hysteresis loss
 mechanical loss

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Electrical Machines
Interpoles in a DC motor must be

 Series excited and should have the same polarity as that of the ahead main pole in the direction of rotation of armature.
 Series excited and should have the same polarity as that of the behind main pole in the direction of rotation of armature.
 Shunt excited and should have the same polarity as that of the ahead main pole in the direction of rotation of armature.
 Shunt excited and should have the same polarity as that of the behind main pole in the direction of rotation of armature.

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Electrical Machines
The factors that are responsible for decrease in terminal voltage of a shunt generator are

  armature resistance, effect of armature reaction.
 armature resistance, inter poles, armature.
 armature resistance, effect of armature reaction.
  reduction in field current, effect of armature reaction, armature.

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Electrical Machines
Which of the following is done in speed control of DC motor by field flux control?

 Inserting an additional resistance in the field circuit.
 Inserting an additional resistance in the armature circuit.
 Any of above.
 Inserting resistance to armature circuit and field circuit.

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