Q.#1. The resistance of armature winding depends on (a) length of conductor (b) cross-sectional area of the conductor (c) number of conductors (d) all of the above Ans: (d) all of the above Q.#2. A commutator in a d.c. machine (A) Converts the induced a.c armature voltage into direct voltage. (B) Reduces power loss in field circuit. (C) Reduces power loss in armature. (D) Is not necessary. Ans: (A) Converts the induced a.c armature voltage into direct voltage. Q.#3. In D.C. generators, the cause of rapid brush wear may be (a) severe sparking (b) any of the above (c) imperfect contact (d) rough commutator surface Ans: (b) any of the above Q.#4. The introduction of interpoles in between the main pole improves the performance of d.c. machines, because (A) A counter e.m.f. is induced in the coil undergoing commutation. (B) The flux waveform is improved with reduction in harmonics. (C) The inequality of air flux on the top and bottom halves of armatur
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