Electrical Machines
The counter (or back) emf in a dc machine is 1. the same as generated emf in a dc motor 2. proportional to field flux and armature speed 3. not the same as generated emf in a dc motor 4.inversely proportional to field flux 5. proportional to number of armature conductors 6. constant from no load to full load From these, the correct answer is

 1, 2, 5
 2, 4, 5, 6
 2, 3, 6
 3, 4, 5

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Electrical Machines
The synchronous reactance( Xs) is the

 reactance due to armature reaction of the machine
 reactance either due to armature reaction or leakage flux
 combined reactance due to armature reaction and leakage flux
 reactance due to leakage flux

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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

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

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