# Commutator Of Direct Current Machine Objective Questions and Answers

46.  The commutator of a DC machine serves the purpose of

A. Changing AC to DC

B. Converting DC into AC

C. Reducing friction

D. Avoiding arc at the brushes

B. Converting DC into AC

47.  To avoid formation of grooves in the commutator

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 of the above

A. The brushes of opposite polarity should track each other

48.  The commutator pitch for Simplex lap winding is

A. + 1

B. - 1

C. + 1 or - 1

D. Average pitch

C. + 1 or - 1

49.  The commutator pitch for simplex wave winding is equal to

A. + 1 or - 1

B. Twice average pitch

C. Average pitch

D. Half average pitch

C. Average pitch

50.  Under commutation results in

A. Sparking at the middle of the brush

B. Sparking at the leading edge of the brush

C. Sparking at that trailing edge of the brush

D. No sparking

C. Sparking at that trailing edge of the brush