Electrical Machines
Which of the following methods are used to control the speed of DC motors is

All of these
 supply voltage control
 armature circuit resistance control
 field current control

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Electrical Machines
In a 3 - Φ induction motor

  none of them.
  power factor at starting in the same as that while running.
  power factor at starting is high as compared to that while running.
  power factor at starting is low as compared to that while running.

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Electrical Machines
The speed of a DC series motor is

 Proportional to field current.
 Proportional to the square of the armature current.
 Inversely proportional to the armature current.
 Proportional to the armature current.

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