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Fields and Their Consequences

Electromagnetic induction

  • 4 things to know
  • Papers 2 and 3

Overview

Faraday's law and Lenz's law, the emf induced by a moving conductor, and the alternator.

What you need to know

Answer each one before you reveal it.

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Numbers

How is induced emf calculated, and what does Lenz's law state?

Numbers

What is flux linkage, and what emf does a straight conductor induce?

Numbers

What condition does ε = BLv assume, and how does emf vary for a rotating coil?

Numbers

What does ω represent, and at what orientation is the peak emf reached?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Under what two conditions can an electromotive force be induced in a conductor?

    Model answer

    When a conductor moves through a magnetic field, or when a magnetic field changes around a stationary conductor.

  2. 2

    State Faraday's law of electromagnetic induction.

    Model answer

    The magnitude of the induced electromotive force equals the rate of change of magnetic flux linkage through the circuit.

  3. 3

    State Lenz's law.

    Model answer

    The direction of the induced electromotive force is such that it opposes the change in flux that produces it.

  4. 4

    Write the equation for the induced electromotive force in terms of the number of turns and rate of change of magnetic flux.

    Model answer

    ε = N(ΔΦ/Δt), where N is the number of turns and ΔΦ/Δt is the rate of change of magnetic flux.

  5. 5

    In the equation ε = N(ΔΦ/Δt), what does the term ΔΦ represent?

    Model answer

    The change in magnetic flux through the coil.

  6. 6

    Calculate the induced emf when number of turns = 306, change in magnetic flux = 0.419 Wb, time interval = 0.24 s.

    Model answer

    Induced emf = 306 × 0.419 ÷ 0.24 = 534 V.

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