VCE · Topic explainer
What is Faraday’s law of induction?
Faraday’s law relates induced electromotive force to the rate of change of magnetic flux linkage. For N identical turns, the average emf is −NΔΦ/Δt, where Φ is the flux through one turn. Faster changes or more turns give a larger magnitude. The negative sign represents the direction described by Lenz’s law.
Worked example
A coil of 50 turns experiences a change of 0.004 Wb per turn over 0.10 s. The magnitude of the average emf is 50 × 0.004 ÷ 0.10 = 2.0 V.
If a current can flow, its magnetic field opposes the change in flux. When an external field through the coil increases, the induced field opposes the increase. The calculated emf does not require a closed circuit, but an induced current does.
Official exam practice
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