Electrical Machines
In case the conditions for maximum power for DC motor are established, the efficiency of the motor will be

 Any where between 75 % and 90 %.
 Less than 50 %
 Around 100 %.
 Around 90 %

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Electrical Machines
The following statements relate to compensating winding (CW) and interpole winding (IW) of a dc machine : 1. CW neutralizes the armature reaction under a pole pitch 2. IW is connected in series with armature circuit 3. IW produces mmf in the commutating zone only 4. CWmmf is directed along the brush axis 5. Mmf produced by IW is equal to armature mmf From these, the correct statements are

 1, 2, 3, 4 and 5
 2, 3, 4
 2, 3, 4, 5
 1, 3, 4, 5

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Electrical Machines
With the increase in speed of DC motor

 Back emf falls and line current increase.
  Back emf increase but line current falls.
 Both back emf as well as line current increase.
 Both back emf as well as line current fall.

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