22. Each commutator segment is connected to the armature conductor by means of
A. insulator
B. copper lug
C. resistance wire
D. carbon brush
23. In a dc generator, sparking between brushes and commutator surface may be due to
A. overcommutation
B. undercommutation
C. to rapid reversal of current
D. any of the above
24. Brushes for commutators for 220 V dc generator are generally made of
A. copper
B. carbon copper
C. electrographite
D. graphited copper
25. Commutato r of a dc machine acts as a
A. fullwave recter
B. halfwave rectifier
C. inverter
D. controlled rectifier
26. The maximum nuber of brushes which machine may be used in an electrical machine isnumber of poles i the machine equal to
A.1
B.2
C.4
D. either (a) or (b) above
27. For a lapature with Z conductors and P poles, the maximum number of equalizer rings required are
A. P
B.(d)2Z/P
C.Z/(2P)
D.
28. If in is the degree of multiplicity and p is the number of poles, the number of parallel paths in a wave winding will be
A.2
B. 2m
C. mp
D. 2 rap
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