A. brushes should be of proper grade and size
B. brushes should smoothly run in the holders
C. smooth, concentric commutator properly undercut
D. all of the above
Related Mcqs:
- 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. none - In case of D.C. machines, mechanical losses are primary function of____________?
A. current
B. voltage
C. speed
D. none of above - Brushes of D.C. machines are made of_________?
A. carbon
B. soft copper
C. hard copper
D. all of above - For a D.C. machines laboratory following type of D.C. supply will be suitable___________?
A. rotary converter
B. mercury are rectifier
C. induction motor D.C. generator set
D. synchronous motor D.C. generator set - According to Fleming’s right-hand rule for finding the direction of induced e.m.f., when middle finger points in the direction of induced e.m.f., forefinger will point in the direction of____________?
A. motion of conductor
B. lines of force
C. either of the above
D. none of the above - If B is the flux density, I the length of conductor and v the velocity of conductor, then induced e.m.f. is given by______________?
A. Blv
B. Blv2
C. Bl2v
D. Bl2v2 - Armature coil is short circuited by brushes when it lies_____________?
A. along neutral axis
B. along field axis
C. in any of the above positions
D. in none of the above positions - 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 above - Following D.C. generator will be in a position to build up without any residual magnetism in the poles______________?
A. series generator
B. shunt generator
C. compound generator
D. self-excited generator - 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
