DC Generators - Interview Questions | Exam2Win

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21. In a commutator

A. copper is harder than mica

B. mica and copper are equally hard

C. mica is harder than copper

D. none of the above

Explanation:

22. 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

Explanation:

23. The material for commutator brushes is generally

A. mica

B. copper

C. cast iron

D. carbon

Explanation:

24. Iron losses in a D.C. machine are independent of variations in

A. speed

B. load

C. voltage

D. speed and voltage

Explanation:

25. Copper brushes in D.C. machine are used

A. where low voltage and high currents are involved

B. where high voltage and small cur-rents are involved

C. in both of the above cases

D. in none of the above cases

Explanation: