ENGINEERING CAREER AND STUDY MATERIALS

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...