Brush gear for DC machines have brushes made from carbon because they:
1. are softer
2. wear to a smooth finish
3. are low cost
4. can produce large quantities of heat
5. have a low coefficient of friction
a) 2, 3, 5
b) 1, 3, 4
c) 1, 2, 5
d) 3, 4, 5
e) 2, 4, 5
Answer: C