A. mica
B. copper
C. cast iron
D. carbon
Related Mcqs:
- In D.C. generators, the brushes on commutator remain in contact with conductors which_________________?
A. lie under south pole
B. lie under north pole
C. lie under interpolar region
D. are farthest from the poles - The number of brushes in a commutator depends on______________?
A. speed of armature
B. type of winding
C. voltage
D. amount of current to be collected - If brushes of a D.C. generator are moved in order to bring these brushes in magnetic neutral axis, there will be________________?
A. demagnetisation only
B. cross magnetisation as well as mag¬netisation
C. crossmagnetisation as well as demagnetising
D. cross magnetisation only - The insulating material used between the commutator segments is normally_____________?
A. graphite
B. paper
C. mica
D. insulating varnish - The commutator segments are connected to the armature conductors by means of___________?
A. copper lugs
B. resistance wires
C. insulation pads
D. brazing - In case of D.C. machine winding, number of commutator segments is equal to______________?
A. number of armature coils
B. number of armature coil sides
C. number of armature conductors
D. number of armature turns - 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 - 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. poles - Copper brushes in D.C. machine are used_____________?
A. where low voltage and high currents are involved
B. where high voltage and small cur-rents are involved
C. in both of the above cases
D. in none of the above cases - In a D.C. generator in order to reduce sparking at brushes, the self-induced e.m.f. in the coil is neutralised by all of the following except______________?
A. interpoles
B. dummy coils
C. compensating winding
D. shifting of axis of brushes
