Free daily NEET & JEE PYQs, quizzes & mock tests on TelegramJoin free →

JEE Main Physics: Electromagnetic induction: Faraday's law and Lenz's law Practice Questions

14 free multiple-choice questions on Electromagnetic induction: Faraday's law and Lenz's law (Electricity and Magnetism) for JEE Main Physics, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.

Practice thousands more JEE Main questions in the app →

  1. Q1. If the magnetic flux linked with a closed loop remains constant over time, what is the induced EMF in that loop?

    • AEMF proportional to the rate of change of flux
    • BEMF proportional to the magnetic field
    • CZero EMF
    • DMaximum EMF
    Show answer & explanation

    Correct answer: C — Zero EMF

    Faraday's law states that EMF is induced only when there is a change in magnetic flux. If the flux is constant (Δφ_B = 0), the induced EMF is zero.

  2. Q2. The induced EMF in a coil is directly proportional to the rate of change of magnetic flux. If the magnetic flux linked with a coil changes uniformly over time, the induced EMF will be:

    • AExponentially proportional to time
    • BConstant
    • CZero
    • DLinearly proportional to time
    Show answer & explanation

    Correct answer: D — Linearly proportional to time

    Faraday's law mathcalE = -dφ_B/dt shows that the induced EMF is proportional to the time derivative of the flux change. If the flux changes uniformly over time, the rate of change (dφ_B/dt) is constant, meaning the induced EMF is constant (linear dependence on time).

  3. Q3. Faraday's law of electromagnetic induction states that the magnitude of the induced electromotive force (EMF) in a closed circuit is proportional to:

    • Athe magnetic flux divided by the time interval
    • Bthe current flowing in the circuit
    • Cthe rate of change of magnetic flux through the loop
    • Dthe magnetic field strength times the area of the loop
    Show answer & explanation

    Correct answer: C — the rate of change of magnetic flux through the loop

    Faraday's law states that the induced EMF (mathcalE) is equal to the negative rate of change of magnetic flux (Φ_B) linked with the circuit.

  4. Q4. Which of the following statements correctly describes the condition necessary for an EMF to be induced in a coil?

    • AThe magnetic flux linked with the coil must be constant.
    • BThe magnetic flux linked with the coil must change over time.
    • CThe magnetic field must be static.
    • DThe magnetic field must be non-uniform across the coil.
    Show answer & explanation

    Correct answer: B — The magnetic flux linked with the coil must change over time.

    According to Faraday's law, an EMF is induced only when there is a change in magnetic flux (dΦ_B/dt ≠ 0).

  5. Q5. When a magnetic field passing through a loop is uniformly changing, the induced EMF will be maximum when the magnetic field changes at the:

    • Aslowest possible rate
    • Bconstant rate
    • Cfastest possible rate
    • Dzero rate
    Show answer & explanation

    Correct answer: C — fastest possible rate

    Since ε∝ dφ_B/dt, the maximum induced EMF occurs when the rate of change of magnetic flux is maximum, which corresponds to the fastest rate of change of the magnetic field.

  6. Q6. Lenz's law is a statement of which principle?

    • AConservation of Charge
    • BConservation of Magnetic Flux
    • CConservation of Energy
    • DConservation of Momentum
    Show answer & explanation

    Correct answer: C — Conservation of Energy

    Lenz's law is a consequence of the conservation of energy. It dictates the direction of the induced current to oppose the change in magnetic flux that caused it.

  7. Q7. According to Faraday's law of electromagnetic induction, the magnitude of the induced electromotive force (EMF) in a circuit is directly proportional to the:

    • Aarea of the loop
    • Brate of change of magnetic flux linked through the loop
    • Cdirection of the magnetic field
    • Drate of change of magnetic field strength
    Show answer & explanation

    Correct answer: B — rate of change of magnetic flux linked through the loop

    Faraday's law states that the magnitude of the induced EMF (ε) is equal to the rate of change of magnetic flux (φ_B) linked with the circuit. ε= -dφ_B/dt (magnitude is proportional to the rate of change of flux).

  8. Q8. The magnetic flux (φ_B) through a loop of area A is given by φ_B = BA cos θ. If the area A of the loop is doubled while the angle θ remains constant, the magnetic flux will:

    • ADouble
    • BHalve
    • CRemain the same
    • DQuadruple
    Show answer & explanation

    Correct answer: A — Double

    Magnetic flux is directly proportional to the area of the loop (φ_B ∝ A). If the area is doubled, the magnetic flux is also doubled.

  9. Q9. Lenz's Law dictates the direction of the induced current. If a magnetic dipole enters a region where the field strength is decreasing, the induced magnetic field will:

    • ARemain unchanged
    • BOppose the motion of the dipole
    • CDecrease the external field
    • DIncrease the external field
    Show answer & explanation

    Correct answer: C — Decrease the external field

    Lenz's law states that the induced field opposes the change in flux. If the external field is decreasing (flux change is negative), the induced field must act in the same direction as the external field to try and maintain the flux, hence it will try to increase the field strength in that region.

  10. Q10. When a conductor moves into a region of stronger magnetic field, the magnetic flux linked with the conductor changes. According to Lenz's law, the induced current will flow in a direction that creates a magnetic field which:

    • Ais opposite to the direction of motion.
    • Bis parallel to the motion.
    • Copposes the motion.
    • Denhances the original magnetic field.
    Show answer & explanation

    Correct answer: A — is opposite to the direction of motion.

    Since the field is stronger (increasing flux), the induced effect must oppose this increase, meaning the induced field opposes the motion that caused the change.

  11. Q11. Lenz's law implies that the direction of the induced current is always such that the magnetic field it produces attempts to:

    • Aremain unchanged
    • Bincrease the magnetic flux
    • Coppose the change in flux
    • Daid the change in flux
    Show answer & explanation

    Correct answer: C — oppose the change in flux

    Lenz's law dictates that the induced effect (the magnetic field created by the current) always acts to oppose the change in magnetic flux that produced it.

  12. Q12. Lenz's law is a consequence of the conservation of energy. It states that the direction of the induced current is always such that it produces a magnetic field that:

    • Ais always directed towards the source of the changing flux
    • Bopposes the change in magnetic flux
    • Cis perpendicular to the original magnetic field
    • Dis parallel to the original magnetic field
    Show answer & explanation

    Correct answer: B — opposes the change in magnetic flux

    Lenz's law dictates that the induced effect (current) opposes the change that caused it (the change in magnetic flux).

  13. Q13. Magnetic flux (Φ_B) through a surface is defined as the product of the magnetic field (B) and the area (A) of the surface. If the magnetic field is uniform and perpendicular to the area, the flux is given by:

    • AB² A
    • BA/B
    • CB/A
    • DB · A
    Show answer & explanation

    Correct answer: D — B · A

    Magnetic flux is calculated as Φ_B = B · A, provided the field is perpendicular to the area.

  14. Q14. If the magnetic flux linked through a circuit is changing at a constant rate, how is the induced EMF related to the rate of change of magnetic flux?

    • AEMF is directly proportional to the rate of change of magnetic flux
    • BEMF is proportional to the area of the loop
    • CEMF is proportional to the magnetic flux itself
    • DEMF is inversely proportional to the rate of change of magnetic flux
    Show answer & explanation

    Correct answer: A — EMF is directly proportional to the rate of change of magnetic flux

    Faraday's Law states that the magnitude of the induced EMF is directly proportional to the rate at which the magnetic flux linked through the circuit is changing. Mathematically, ε= -N dφ_b/dt. Thus, the EMF is directly proportional to the rate of change of magnetic flux, dφ_b/dt.

Keep going — practice on Padhai Karlo

Padhai Karlo gives you unlimited JEE Main practice: chapter-wise questions, timed quizzes, and full mock tests with an All-India Rank — free to start.

Get the free Android app →

More Electricity and Magnetism topics

← All Electricity and Magnetism practice