a) The law of electromagnetic induction b) Interaction between magnetic field and current carrying conductor c) Interaction between two electric fields d) Interaction between magnetic field and electric field Ans: (b)
a) D.c. machines b) A.c. machines c) Electro-mechanical convertors d) Machines using electromagnetic induction Ans: (c)
a) Rotating armature and fixed field b) Rotating field and fixed armature c) Either (a) or (b) d) None of these Ans: (a)
a) Flux linkage with conductors is maximum b) Flux linkage with conductors is minimum c) Rate of change of flux linkage is maximum d) Rate of change of flux linkage is minimum Ans: (c)
a) Sparking at the trailing edge of the brush b) Sparking at the leading edge of the brush c) Sparking at the middle of the brush d) No sparking at all Ans: (a)
a) To provide easy speed control b) To change ac voltage into dc voltage c) To change dc voltage into dc voltage d) To improve commutation Ans: (b)
a) Converts mechanical energy into electrical energy b) Has magnetic poles c) Works as a motor d) Is a dc machine Ans: (a)
a) Magnetic poles b) Electric brushes c) Armature d) Commutator Ans: (d)
a) Totally cross-magnetizing b) Totally magnetizing c) Totally demagnetizing d) Partly demagnetizing and partly cross-magnetizing Ans: (d)
a) Reducing to number of turns in the armature and segments of commutator b) Increasing the resistance of brushes c) Neutralizing the reactance voltage by producing a reverse emf in the coil undergoing commutation d) All of these Ans: (d)