The field coils of D.C. generator are usually made of_____________?
The field coils of D.C. generator are usually made of_____________?
A. mica
B. copper
C. cast iron
D. carbon
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The critical resistance of the D.C. generator is the resistance of_____________?
The critical resistance of the D.C. generator is the resistance of_____________?A. field
B. brushes
C. armature
D. loadCompensating windings are used in D.C. generators______________?
Compensating windings are used in D.C. generators______________?A. mainly to reduce the eddy currents by providing local short-circuits
B. to provide path for the circulation of cooling air
C. to neutralise the cross-magnetising effect of the armature reaction
D. none of the aboveIn case of D.C. machines, mechanical losses are primary function of____________?
In case of D.C. machines, mechanical losses are primary function of____________?A. current
B. voltage
C. speed
D. none of aboveOpen circuited armature coil of a D.C. machine is________________?
Open circuited armature coil of a D.C. machine is________________?A. identified by the scarring of the commutator segment to which open circuited coil is connected
B. indicated by a spark completely around the commutator
C. both A. and (b)
D. none of the aboveFor both lap and wave windings, there are as many commutator bars as the number of_____________?
For both lap and wave windings, there are as many commutator bars as the number of_____________?A. slots
B. armature conductors
C. winding elements
D. polesThe purpose of providing dummy coils in a generator is____________?
The purpose of providing dummy coils in a generator is____________?A. to reduce eddy current losses
B. to enhance flux density
C. to amplify voltage
D. to provide mechanical balance for the rotor