Electrical Machines
Consider the following statements regarding dc machines : 1. possible resistance of shunt-field winding is 1 Ω 2. possible resistance of series-field winding is 1 Ω 3. electrographite brushes are used for 230 V, 10 A machines 4. Copper-graphite brushes are used for 230 V, 10 A machines 5. Possible armature-circuit resistance is 1 Ω From these, the correct statements are

 2, 3 , 5
 2, 4 ,5
 1, 4
 1, 3, 5

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

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

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