Electrical Machines
DC motors are stopped by opening line switches and not by forcing the handle of the motor starter back to OFF position. This is due to occurance of

 None of these.
 Both of above.
 Heavy sparking at brushes.
 Heavy sparking at the first stud of starting resistance steps.

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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

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

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Electrical Machines
If the frequency of input voltage of a transformer is increased keeping the magnitude of voltage unchanged, then

 Pe will increase but Ph will decrease
 Ph will increase but Pe will decrease
 Ph will decrease but Pe will remain same
 both hysteresis loss(Ph) and eddy current loss(Pe) will increase

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