NEET Physics Magnetic Flux Faradays and Lenzs Law MCQs Set A

Question: According to Faraday’s law of electromagnetic induction
a) electric field is produced by time varying magnetic flux
b) magnetic field is produced by time varying electric flux
c) magnetic field is associated with a moving charge
d) None of these
Answer: electric field is produced by time varying magnetic flux

Question: Lenz’s law is a consequence of the law of conservation of
a) energy
b) charge
c) mass
d) momentum
Answer: energy

Question: A magnet is moved towards a coil (i) quickly (ii) slowly, then the induced e.m.f. is
a) larger in case (i)
b) smaller in case (i)
c) equal in both the cases
d) larger or smaller depending upon the radius of the coil
Answer: larger in case (i)

Question:   A current carrying infinitely long wire is kept along the diameter of a circular wire loop, without touching it, the correct statement(s) is(are)
I. The emf induced in the loop is zero if the current is constant.
II. The emf induced in the loop is finite if the current is constant.
III. The emf induced in the loop is zero if the current decreases at a steady rate
a) I only
b) I and II
c) II only
d) I, II and III
Answer: I only

Question: An induced e.m.f. is produced when a magnet is plunged into a coil. The strength of the induced e.m.f. is independent of
a) the resistivity of the wire of the coil
b) speed with which the magnet is moved
c) number of turns of coil
d) the strength of the magnet
Answer: the resistivity of the wire of the coil

Question: A coil of insulated wire is connected to a battery. If it is taken to galvanometer, its pointer is deflected, because
a) the induced current is produced
b) the coil acts like a magnet
c) the number of turns in the coil of the galvanometer are changed
d) None of these
Answer: the induced current is produced

Question:  Two different wire loops are concentric and lie in the same plane. The current in the outer loop (I) is clockwise and increases with time. The induced current in the inner loop

a) is counter clockwise
b) has a direction that depends on the ratio of the loop radii
c) is zero
d) is clockwise
Answer: is counter clockwise

Question: Two identical coaxial circular loops carry a current i each circulating in the same direction. If the loops approach each other, you will observe that the current in
a) each decreases
b) each remains the same
c) one increases whereas that in the other decreases
d) each increases
Answer: each decreases

Question: In electromagnetic induction, the induced charge is independent of
a) time
b) None of these
c) change of flux
d) resistance of the coil
Answer:  time

Question: Flux of magnetic field through an area bounded by a closed conducting loop can be changed by changing
a) All of the above
b) area of the loop
c)

d)

Answer:  All of the above

Question:

a)

b)

c) None of these

d)

Answer:

Question: A conducting loop is placed in a uniform magnetic field with its plane perpendicular to the field. An e.m.f. is inducedin the loop, if
a) it is rotated about its diameter
b) it is rotated about its axis
c) it is translated
d) None of these
Answer:  it is rotated about its diameter

Question:

a) The induced e.m.f. opposes the change in the magnetic flux
b) The induced e.m.f. is opposite to the direction of the flux
c) None of the above
d) The induced e.m.f. is produced only when the magnetic flux decreases.
Answer: The induced e.m.f. opposes the change in the magnetic flux

Question:

a)

b)

c)

d)

Answer:

Question:  Whenever the magnetic flux linked with a coil changes, an induced e.m.f.is produced in the circuit. The e.m.f. lasts
I. for a short time
II. for a long time
III. so long as the change in flux takes place
The correct statement(s) is/are
a) III only
b) II and III
c) I and II
d) I and III
Answer:  III only

Question:

a) 2
b) 6
c) 4
d) 8
Answer:  2

Question:

a) 0.5 weber
b) 2.0 weber
c)

d)

Answer:  0.5 weber

Question:

a) 31 mV; left to right
b) 31 mV; right to left
c) 39 mV; left to right
d) 39 mV; right to left
Answer:  31 mV; left to right

Question:

a) Assertion is correct, reason is correct; reason is a correct explanation for assertion
b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
c) Assertion is correct, reason is incorrect
d) Assertion is incorrect, reason is correct
Answer: Assertion is correct, reason is correct; reason is a correct explanation for assertion

Question:  A coil having an area A₀ is placed in a magnetic field which changes from B₀ to 4 B₀ in time interval t. The e.m.f. induced in the coil will be
a)

b)

c)

d) None of these

Answer:

Question:

a) B to A and D to C
b) A to B and D to C
c) A to B and C to D
d) B to A and C to D
Answer:  B to A and D to C

Question:

a)

b)

c)

d)

Answer:

Question:  The north pole of a bar magnet is moved towards a coil along the axis passing through the centre of the coil and perpendicular to the plane of the coil. The direction of the induced current in the coil when viewed in the direction of the motion of the magnet is 
a) anti-clockwise
b) no current in the coil
c) either clockwise or anti-clockwise
d) clockwise
Answer: anti-clockwise

Question: If a current increases from zero to one ampere in 0.1 second in a coil of 5 mH, then the magnitude of the induced e.m.f. will be
a) 0.05 volt
b) 0.005 volt
c) 0.5 volt
d) 5 volt
Answer: 0.05 volt

Question: A coil has 200 turns and area of 70 cm². The magnetic field perpendicular to the plane of the coil is 0.3 Wb/m² and take 0.1 sec to rotate through 180º.The value of the induced e.m.f. will be
a) 8.4 V
b) 84 V
c) 42 V
d) 4.2 V
Answer:  8.4 V

Question:

a) 0.5 A
b) 0.1 A
c) 2 A
d) 1 A
Answer:  0.5 A

Question:

a)

b)

c)

d)

Answer:

Question:Assertion : An emf can be induced by moving a conductor in a magnetic field.
Reason : An emf can be induced by changing the magnetic field.
a) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
b) Assertion is correct, reason is incorrect
c) Assertion is incorrect, reason is correct.
d) Assertion is correct, reason is correct; reason is a correct explanation for assertion
Answer: Assertion is correct, reason is correct; reason is not a correct explanation for assertion

Question:

a) 0.2 A
b) 0.6 A
c) 1.2 A
d) 0.8 A
Answer: 0.2 A

Question:  A conducting circular loop is placed in a uniform magnetic field, B = 0.025 T with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of 1 mm s^–1. The induced e.m.f. when the radius is 2 cm, is

a)

b)

c)

d)

Answer:

Question:  The north pole of a long horizontal bar magnet is being mbrought closer to a vertical conducting plane along the perpendicular direction. The direction of the induced current in the conducting plane will be
a) anticlockwise
b) vertical
c) horizontal
d) clockwise
Answer: anticlockwise

Question: A coil of 50 turns is pulled in 0.02 s between the poles of a magnet, where its area includes 31 × 10^–6 Wb to 1 × 10^–6Wb. The average e.m.f. is
a) 7.5 × 10^–2 V
b) 7.5 × 10^–3 V
c) zero
d) None of these
Answer: 7.5 × 10^–2 V

Question:  A long solenoid having 200 turns per cm carries a current of 1.5 amp. At the centre of it is placed a coil of 100 turns of cross-sectional area 3.14 × 10^–4 m² having its axis parallel to the field produced by the solenoid. When the direction of current in the solenoid is reversed within 0.05 sec, the induced e.m.f. in the coil is
a) 0.048 V
b) 0.0048 V
c) 48 V
d) 0.48 V
Answer:  0.048 V

Question:

a) 0.1 C
b) 1 C
c) 2 C
d) 0.2 C
Answer: 0.1 C

Question:   A thin circular ring of area A is held perpendicular to a uniform magnetic field of induction B. A small cut is made in the ring and a galvanometer is connected across the endssuch that the total resistance of the circuit is R. When the ring is suddenly squeezed to zero area, the charge flowing through the galvanometer is

a)

b)

c) ABR

d)

Answer:

Question:  A metal disc of radius 100 cm is rotated at a constant angular speed of 60 rad/s in a plane at right angles to an external field of magnetic induction 0.05 Wb/m². The emf induced between the centre and a point on the rim will be
a) 1.5 V
b) 6 V
c) 9 V
d) 3 V
Answer: 1.5 V

Question: A rectangular coil of 100 turns and size 0.1 m × 0.05 m is placed perpendicular to a magnetic field of 0.1 T. The induced e.m.f. when the field drops to 0.05 T in 0.05s is
a) 0.5 V
b) 1.0 V
c) 1.5 V
d) 2.0 V
Answer: 0.5 V

Question:

a) 0.5 A
b) 5 A
c) 50 A
d) 1 A
Answer:  0.5 A

Question:

a) 0.02 amp
b) 0.7 amp
c) 0.04 amp
d) 0.01 amp
Answer: 0.02 amp