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

 1, 3, 5
 2, 3 , 5
 2, 4 ,5
 1, 4

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Electrical Machines
In a loaded DC generator, if the brushes are given a shift from the interpolar axis in the direction of rotation, then the commutation will

 deteriorate with rise in terminal voltage.
 deteriorate with fall of terminal voltage.
 improve with fall of terminal voltage.
 improve with rise in terminal voltage.

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