Brushes of D.C. machines are made of_________?
Brushes of D.C. machines are made of_________?
A. carbon
B. soft copper
C. hard copper
D. all of above
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In a four-pole D.C. machine____________?
In a four-pole D.C. machine____________?A. all the four poles are north poles
B. alternate poles are north and south
C. all the four poles are south poles
D. two north poles follow two south polesA cumulatively compounded long shunt generator when operating as a motor would be____________?
A cumulatively compounded long shunt generator when operating as a motor would be____________?A. cumulatively compounded long shunt
B. deferentially compounded long shunt
C. cumulatively compounded short shunt
D. differentially compounded short shuntTo achieve sparkless commutation brushes of a D.C. generator are rockedm ahead so as to bring them?
To achieve sparkless commutation brushes of a D.C. generator are rockedm ahead so as to bring them?A. just ahead of magnetic neutral axis
B. in magnetic neutral axis
C. just behind the magnetic neutral axis
D. noneIn D.C. generators the polarity of the interpoles_____________?
In D.C. generators the polarity of the interpoles_____________?A. is the same as that of the main pole ahead
B. is the same as that of the immediately preceding pole
C. is opposite to that of the main pole ahead
D. is neutral as these poles do not play part in generating e.m.f.For 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. polesTo avoid formation of grooves in the commutator of a D.C. machine?
To avoid formation of grooves in the commutator of a D.C. machine?A. the brushes of opposite polarity should track each other
B. the brushes of same polarity should track each other
C. brush position has no effect on the commutator grooving
D. None