22.  Each commutator segment is connected to the armature conductor by means of
A. insulator
B. copper lug
C. resistance wire
D. carbon brush

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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

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24.  Brushes for commutators for 220 V dc generator are generally made of
A. copper
B. carbon copper
C. electrographite
D. graphited copper

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25.  Commutato r of a dc machine acts as a
A. fullwave recter
B. halfwave rectifier
C. inverter
D. controlled rectifier

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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

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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.

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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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