a) Three-phase mercury arc rectifier b) Six-phase mercury arc rectifier c) twelve-phase mercury arc rectifier d) Single phase mercury arc rectifier Ans: (a)
a) The power factor will increase b) The power factor will decrease c) The magnetizing current of the rotor will increase d) The magnetizing current of the rotor will decrease e) The speed of the motor will decrease Ans: (d)
a) One slip rings b) two slip rings c) three slip rings d) zero slip rings Ans: (d)
a) motor will stop b) motor will run at its normal speed in the same direction as it was running c) the direction of rotation will reverse d) motor speed will increase Ans: (c)
a) a d.c. series motor b) a d.c. shunt motor c) a d.c. compound motor d) magnetic amplifier Ans: (c)
a) A b) B c) C d) D Ans: (b)
a) Tachometer b) Voltmeter c) Ammeter d) Galvanometer Ans: (a)
a) R2 (1/s – 1) b) R2 (1/s – 1) c) R2 (s – 1) d) 1/R2 (s – 1) Ans: (b)
Where R2 is the resistance of the rotor in terms of secondary and s is the slip of motor.
a) Will decrease b) Will increase c) Will not change d) Will reach nearly zero Ans: (b)
a) The yoke b) The pole shoe c) The armature d) The field Ans: (b)
a) The size of core will decrease b) Less copper will be used c) Core losses will decrease d) Voltage output will decrease Ans: (a)
a) Sinusoidal voltage b) Direct voltage c) Sinusoidal with even harmonics d) Sinusoidal with oil harmonics Ans: (a)
a) No magnetic field b) No magnetic unless the poles are far apart c) A strong magnetic field d) A magnetic field if the poles tough Ans: (c)
a) Induced poles opposite from the original poles b) Induced poles the same as the original field c) Two north poles d) An induced magnetic field but no induced pole Ans: (a)
a) Iron, steel, and nickel are magnetic materials. b) Copper, iron, steel, and air are magnetic materials. c) Paper, wood, and steel are magnetic materials. d) Iron is magnetic materials but steel is non-magnetic. Ans: (a)