Electrical Machines
In a DC generator, the armature reaction results in

 magnetization of leading and demagnetization of trailing pole tip.
  demagnetization of leading & magnetization of trailing pole tip.
 demagnetization of centers of poles.
  magnetization of inter poles.

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Electrical Machines
The 3 - Φ induction motors are, by a very considerable margin, the most widely used AC motors as

  they are capable of operation under range of leading and lagging pf.
  they have very good speed regulation.
  these are cheaper in cost, simple and rugged in construction.
  they have maximum efficiency and maximum starting torque.

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