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

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

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Electrical Machines
The armature mmf of a DC machine has

  triangular space distribution and rotates at the speed of armature.
 stepped distribution and rotates at the speed of armature.
  triangular space distribution and is stationary in space.
  trapezoidal space distribution and is stationary in space.

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