NEET Physics Transformer and LC Oscillations MCQs Set A

Question:  A transformer is employed to
a) obtain a suitable A.C. voltage
b) obtain a suitable D.C. voltage
c) convert D.C. into A.C.
d) convert A.C. into D.C.
Answer: obtain a suitable A.C. voltage

Question: The transformer voltage induced in the secondary coil of a transformer is mainly due to
a) a varying magnetic field
b) a varying electric field
c) the vibrations of the primary coil
d) the iron core of the transformer
Answer: a varying magnetic field

Question: The loss of energy in the form of heat in the iron core of a transformer is
a) iron loss
b) mechanical loss
c) copper loss
d) None of these
Answer: iron loss

Question: Quantity that remains unchanged in a transformer is
a) frequency
b) voltage
c) None of these
d) current
Answer:  frequency

Question: A step up transformer operates on a 230 V line and supplies a current of 2 ampere. The ratio of primary and secondary winding is 1:25 . The current in primary is
a) 50 A
b) 15 A
c) 12.5 A
d) 25 A
Answer: 50 A

Question: In a transformers, number of turns in primary coil are 140 and that in secondary coil are 280. If current in primary coil is 4A, then that in secondary coil is
a) 2 A
b) 6 A
c) 10 A
d) 4 A
Answer: 2 A

Question:  A transformer is used to light a 140 W, 24 V bulb from a 240 V a.c. mains. The current in the main cable is 0.7 A. The efficiency of the transformer is
a) 83.3 %
b) 16.7 %
c) 36.2 %
d) 63.8 %
Answer: 83.3 %

Question: Eddy currents in the core of transformer can't be developed by
a) taking laminated transformer
b) making step down transformer
c) using a weak a.c. at high potential
d) increasing the number of turns in secondary coil
Answer: taking laminated transformer