a) Get sparking commutation b) Avoid unequal current distribution at brushes c) Both (a) and (b) d) To neutralize the armature reaction Ans: (c)
a) Winding distribution b) Armature reactance c) High constant resistance of the brushes d) Reactance voltage in coil undergoing commutation Ans: (d)
a) Number of poles in the machine b) 4 c) 2 d) Either (a) or (c) Ans: (d)
a) 1 b) 2 c) 4 d) 8 Ans: (c)
a) Fullwave rectifier b) Halfwave rectifier c) Inverter d) Controlled rectifier Ans: (a)
a) Brush off carbon deposits in the commutator b) Provide a path for flow of current c) Prevent overheating of armature winding d) Prevent sparking during commu-tation Ans: (b)
a) Copper b) Carbon copper c) Electrographite d) Graphite copper Ans: (c)
a) Less than 1 kg/cm2 b) About 3 kg/cm2 c) About 5 kg/cm2 d) About 10 kg/cm2 Ans: (a)
a) Rough commutator surface b) Severe sparking c) Imperfect contact with commutator d) Any of these Ans: (d)
a) Keeps stability of supply b) Gives facility of repair which results in fewer breakdown c) Gives facility of an additional unit to be installed as and when required d) All of these Ans: (d)