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
In case of 3 - Φ IM, plugging means

  interchanging two supply phases for quick stopping.
  starting the motor on load which is more than the rated load.
  locking of rotor due to harmonics.
  pulling the motor directly on line without a rotor.

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