JEE Physics Electromagnetic Induction MCQs Set A

Question. An emf can be induced in stationary coil if it is kept in
(a) Time varying magnetic field
(b) Stationary uniform magnetic field
(c) Stationary nonuniform magnetic field
(d) Not possible

Answer: A

Question. The induced e.m.f. in a coil does not depend on
(a) The resistance of the circuit
(b) The rate of change of magnetic flux
(c) The number of turns in the coil
(d) Time of rotation

Answer: A

Question. A cylindrical magnet is kept along the axis of a circular coil. On rotating the magnet about its axis, the coil will have induced in it
(a) No current
(b) A current
(c) Only an e.m.f.
(d) Both an e.m.f. and a current

Answer: A

Question. A magnet is brought near a coil in two ways (i) rapidly (ii) slowly. The induced charge will be
(a) Equal in both the cases
(b) More in case (i)
(c) More in case (ii)
(d) More or less according to the radius of the coil

Answer: A

Question. A circular loop of flexible conducting material is kept in a magnetic field directed perpendicularly into its plane. By holding the loop at diametrically opposite points its is suddenly stretched outwards, then
(a) Clockwise current is induced
(b) No current is induced in the loop
(c) Anti-clockwise current is induced
(d) Only e.m.f. is induced

Answer: A

Question. An aeroplane is flying horizontally with a velocity of 360 km/h. The distance between the tips of the wings of aeroplane is 25 m. The vertical component of earth's magnetic field is 4 × 10^–4 Wb/m². The induced e.m.f. is
(a) 1 V
(b) 100 V
(c) 1 kV
(d) Zero

Answer: A

Question. A coil having 500 square loops each of side 10 cm is placed with its plane perpendicular to a magnetic field which increases at a rate of 1.0 tesla/s. The induced e.m.f. (in volts) is
(a) 5.0
(b) 1.0
(c) 0.1
(d) 0.5

Answer: A

Question. The physical quantity, which is conserved on the basis of Lenz's Law is
(a) Energy
(b) Mass
(c) Momentum
(d) Charge

Answer: A

Question. A metallic ring with a cut is held horizontally and a magnet is allowed to fall vertically through the ring, then the acceleration of this magnet is
(a) Equal to g
(b) Less than g
(c) More than g
(d) Sometimes less and sometimes more than g

Answer: A

Question. A loop of irregular shape made of flexible conducting wire carrying clockwise current is placed in uniform inward magnetic field, such that its plane is perpendicular to the field. Then the loop
(a) All of these
(b) Develops induced current for a short time
(c) Experiences force
(d) Changes to circular loop

Answer: A

Question. Eddy currents are induced when
(a) A metal block is kept in a changing magnetic field
(b) A metal block is kept in a uniform magnetic field
(c) A coil is kept in a uniform magnetic field
(d) Current is passed in a coil

Answer: A

Question. A motor starter
(a) All of these
(b) Offsets the back emf variations
(c) Is a variable resistor
(d) Helps start a DC motor

Answer: A

Question. Which of the following is possible application of an RC circuit?
(a) All of these
(b) Heart pacemakers
(c) Flashing red lights on roadway construction sites
(d) Windshield wipers

Answer: A

Question. The current passing through a choke coil of self inductance 5 H is decreasing at the rate of 2 A/s. The e.m.f. developed across the coil is
(a) 10 V
(b) – 10 V
(c) – 2.5 V
(d) 2.5 V

Answer: A

Question. When the number of turns in a solenoid are doubled without any change in the length of the solenoid, its self inductance becomes
(a) Four times
(b) Eight times
(c) Double
(d) Half

Answer: A

Question. A coil of resistance 20 ohms and inductance 5 H has been connected to a 100 volt battery. The energy stored in the coil is
(a) 62.5 J
(b) 31.25 J
(c) 125 J
(d) 250 J

Answer: A

Question. An inductor is connected to a direct voltage source through a switch. Now
(a) Larger emf is induced when switch is opened
(b) Very large emf is induced in inductor when switch is closed
(c) Large emf is induced whether switch is closed or opened
(d) No emf is induced whether switch is closed or opened

Answer: A

Question. A solenoid has 2000 turns wound over a length of 0.3 m. The area of its cross section is 1.2 × 10^–3 m². Around its central section a coil of 300 turns is wound. If an initial current of 2 A is reversed in 0.25 s, the e.m.f. induced in the coil is equal to
(a) 4.8 × 10^–2 V
(b) 6 × 10^–4 V
(c) 2.4 × 10^–2 V
(d) 48 kV

Answer: A

Question. With the decrease of current in the primary coil from 2 A to zero in 0.01s, the e.m.f. generated in the secondary coil is 1000 V. The mutual inductance of the two coil is
(a) 5.00 H
(b) 10.00 H
(c) 2.50 H
(d) 1.25 H

Answer: A

Question. Two coaxial coils are very close to each other and their mutual inductance is 5 mH. If a current 50 sin 500t is passed in one of the coils then the peak value of induced e.m.f. in the secondary coil will be
(a) 125 V
(b) 150 V
(c) 500 V
(d) 5000 V

Answer: A

Question. The coefficient of self induction of two inductor coils are 20 mH and 40 mH respectively. If the coils are connected in series so as to support each other and the resultant inductance is 80 mH then the value of mutual inductance between the coils will be
(a) 10 mH
(b) 5 mH
(c) 20 mH
(d) 40 mH

Answer: A