This HL-only mini-lesson covers Theme D.4 — Electromagnetic induction: magnetic flux, Faraday's and Lenz's laws, motional emf, and generators and transformers.
Work through each screen, answer the questions as you go (some are reasoning, some are calculations) and collect ⭐ stars. Watch for the HL flag on higher-level extensions. Press Start when you're ready.
Magnetic flux Φ measures the field passing through a loop of area A; flux linkage for N turns is NΦ:
Flux is maximum when the field is perpendicular to the plane of the coil (θ = 0, cosθ = 1) and zero when the field lies in the plane (θ = 90°).
A changing flux induces an emf. Faraday's law: the emf equals the rate of change of flux linkage. Lenz's law (the minus sign): the induced current opposes the change that causes it — this is energy conservation.
A 200-turn coil has its flux fall by ΔΦ = 0.010 Wb in Δt = 0.50 s.
ε = N ΔΦ ÷ Δt = 200 × 0.010 ÷ 0.50 = 4.0 V
A rotating coil in a field is an AC generator — the flux linkage varies sinusoidally, inducing an alternating emf. A transformer changes AC voltage using two coils on an iron core:
A transformer only works with alternating current, because a steady current gives constant flux and hence no induced emf in the secondary.
Tap an item, then tap the group it belongs to.
Tap a statement on the left, then its match on the right.
Flux: Φ = BA cosθ; max when field ⟂ coil plane
Faraday: ε = −N ΔΦ/Δt; change is essential
Lenz: induced current opposes the change (energy conservation)
Motional emf: ε = BvL for a rod cutting field lines
Transformer: V_s/V_p = N_s/N_p; AC only
That completes Electromagnetic Induction for IB Diploma Physics HL. Press Finish to see your score.
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