Lesson 7.5.2

7.5.2 Faraday's law and Lenz's law Quiz: Pearson Edexcel Physics, Unit 7

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 7.5.2, Faraday's law and Lenz's law: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 7: Electric and Magnetic Fields, written with Revision Ninja.

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The 20 questions

  1. What does Faraday's law state about the magnitude of an induced e.m.f.?

    • It equals the current multiplied by the resistance of the circuit
    • It equals the magnetic flux linkage at a single instant
    • It equals the magnetic flux density multiplied by the length of the conductor
    • It equals the rate of change of magnetic flux linkage

  2. What does Lenz's law state about the direction of an induced e.m.f.?

    • The induced e.m.f. acts so as to oppose the change that produces it
    • The induced e.m.f. always acts in the same direction as the change that produces it
    • The induced e.m.f. always acts in the direction of the coil's own resistance
    • The induced e.m.f. always acts at 90 degrees to the change that produces it

  3. Lenz's law is consistent with which fundamental principle?

    • The conservation of baryon number in nuclear reactions
    • The conservation of angular momentum in a rotating coil
    • The conservation of charge in a closed circuit
    • The conservation of energy

  4. In the equation E = -d(N phi)/dt, what does the minus sign represent?

    • The flux linkage is decreasing in every case that is considered
    • The e.m.f. is always negative and so must be reversed in sign
    • The direction of the induced e.m.f., as stated by Lenz's law
    • The coil has a negative resistance that reduces the e.m.f.

  5. A north pole is pushed towards a coil. What polarity does the face of the coil nearest the magnet take, according to Lenz's law?

    • A north pole, so the magnet is attracted
    • A north pole, so the magnet is repelled
    • No pole, because the induced e.m.f. produces no magnetic field
    • A south pole, so the magnet is attracted

  6. The flux through each turn of a 100-turn coil changes from 0.020 Wb to 0.080 Wb in 0.40 s. What is the average induced e.m.f.?

    • 0.15 V
    • 15 V
    • 1.5 V
    • 150 V

  7. The flux linkage through a coil falls from 3.0 Wb to zero in 0.60 s. What is the magnitude of the average induced e.m.f.?

    • 18 V
    • 1.8 V
    • 5.0 V
    • 0.20 V

  8. The flux linkage through a coil decreases steadily at 2.0 Wb s^-1. What is the magnitude of the induced e.m.f.?

    • -2.0 V
    • 4.0 V
    • 2.0 V
    • 0.50 V

  9. On a graph of flux linkage against time, what does the gradient at any point represent?

    • The resistance of the coil at that instant
    • The total charge that has flowed through the coil
    • The magnetic flux density at that instant
    • The induced e.m.f. at that instant

  10. The flux linkage through a coil increases linearly from zero to 0.80 Wb in 2.0 s. What is the e.m.f. during this time?

    • 2.0 V
    • 0.80 V
    • 0.20 V
    • 0.40 V

  11. What does the area under an e.m.f. against time graph represent?

    • The total energy stored in the magnetic field
    • The average power delivered to the circuit
    • The total charge flowing through the circuit
    • The total change in flux linkage

  12. A 60-turn coil has an induced e.m.f. of 3.0 V for 0.50 s. What is the change in flux through each turn?

    • 0.025 Wb
    • 0.25 Wb
    • 0.0025 Wb
    • 0.10 Wb

  13. A bar magnet's south pole is pushed towards a coil. Which face of the coil nearest the magnet is induced to become a south pole, opposing the approach?

    • The face nearest the approaching magnet becomes a north pole, repelling the magnet
    • The face nearest the approaching magnet becomes a south pole, repelling the magnet
    • The face nearest the approaching magnet becomes a north pole, attracting the magnet
    • The induced poles appear on the far face of the coil, away from the magnet

  14. A conducting loop moves out of a uniform magnetic field, so the flux through it decreases. What is the direction of the induced current?

    • In the direction that produces a field at right angles to the original field
    • In the direction that produces a field in the same direction as the original field, opposing the decrease
    • There is no induced current because the loop is leaving the field
    • In the direction that produces a field opposite to the original field, opposing the decrease

  15. A 50-turn coil of area 0.20 m^2 turns from perpendicular to parallel to a uniform field of 0.40 T in 0.10 s. What is the average induced e.m.f.?

    • 4.0 V
    • 80 V
    • 40 V
    • 8.0 V

  16. Why does Lenz's law, with its minus sign, guarantee energy conservation when a magnet is moved into a coil?

    • The induced current is always zero when the magnet is moving, so no energy is transferred
    • The induced current has no effect on the magnet's motion, so the energy comes from the coil's resistance
    • The induced current assists the motion, so extra energy is supplied to the magnet by the coil
    • The induced current opposes the motion, so the work done moving the magnet is converted into electrical energy

  17. A flux linkage changes from 0.50 Wb to 0.20 Wb uniformly over 0.10 s. What is the magnitude of the induced e.m.f.?

    • 0.70 V
    • 7.0 V
    • 3.0 V
    • 0.30 V

  18. A student says the minus sign in E = -d(N phi)/dt can be ignored when working out a magnitude. Which response is correct?

    • The student is right that the magnitude is unaffected, but the sign is needed to give the direction of the induced e.m.f. by Lenz's law
    • The student is wrong, because the minus sign changes the magnitude of the e.m.f. by a factor of two
    • The student is wrong, because the minus sign shows the coil has a negative resistance
    • The student is right in every case, because Lenz's law has no effect on the direction of current

  19. A student claims a coil with constant flux linkage but a steady current flowing through it must have an induced e.m.f. Which response is correct?

    • The student is wrong: an induced e.m.f. depends only on a change in flux linkage, so constant flux linkage induces none
    • The student is right, because any current in a coil always induces an e.m.f. in that coil
    • The student is wrong because currents never flow in coils that are linked with flux
    • The student is right, but only if the coil has more than one turn

  20. A 200-turn coil has the flux through each turn changing at a steady rate of 0.005 Wb s^-1. What is the magnitude of the induced e.m.f.?

    • 0.025 V
    • 1.0 V
    • 0.20 V
    • 40 V

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