Electromagnetic induction – Generator effect, Solenoid and Lenz’s law Simulation
Simulation Description
This simulation models electromagnetic induction – Generator effect and Lenz’s Law — a core AQA GCSE Physics topic (Paper 2, Magnetism and Electromagnetism). A bar magnet moves in and out of a solenoid coil connected to a galvanometer, showing in real time exactly what happens at each stage of the induction process.
The N pole of the magnet (red) enters the coil from outside, inducing an EMF. The galvanometer needle deflects left or right depending on the direction of the induced current, returning to zero when the magnet is stationary — directly mirroring the standard bench experiment students encounter in class. As the magnet moves, amber tangential arrows on the coil show the direction of the induced current; a large arrow inside the coil (red ⊗ or green ⊙) shows the direction of the opposing magnetic field produced by that current, making Lenz’s Law visible rather than abstract. Purple flux arrows inside the solenoid show the magnetic flux threading through the coil, brightening as the magnet approaches and fading as it withdraws. The induced EMF waveform (bottom-left, always visible) shows the characteristic double-peak shape — positive as the magnet enters, zero as it passes the centre, negative as it exits — which connects directly to the idea that it is change in flux, not flux itself, that induces an EMF.
Students can drag the scene freely to inspect the coil, magnet, and galvanometer from any angle. The vertical slider on the left lets them push and pull the magnet manually at their own pace, which is essential for the activity below. The speed slider varies the oscillation rate so classes can observe slow careful entry or fast sweeps. Toggling 🏷 Labels adds the five-step GCSE causal chain at the top and the Φ / I / opposing-field badge on the right. Audio gives an additional sensory channel — a tone rises in pitch and volume with EMF magnitude and is silent when the magnet is stationary.
Suggested Class Activity
“What Happens If…” — Prediction, Observe, Explain Suitable for: GCSE Physics Year 10/11 — Electromagnetic Induction lesson. 25–30 minutes.
Setup (2 min) Display the simulation on the board. Labels off. Students have mini whiteboards or an observation sheet with a blank galvanometer dial and a blank coil diagram.
Stage 1 — Prior knowledge probe (5 min) Pause the simulation with the magnet just outside the coil. Ask: “What will happen to the galvanometer when I push the magnet in? Draw the needle position.” Collect predictions — most students will correctly predict deflection but won’t know direction or what happens at the centre.
Stage 2 — Slow reveal using the slider (8 min) Hand control of the vertical slider to a student (or use it teacher-led on a tablet). Push the magnet slowly into the coil. Ask the class to observe and narrate:
- What does the galvanometer do as the magnet enters?
- What happens when the magnet stops moving inside the coil?
- What happens when it is pulled back out?
Students record their observations. Key target answers: deflection in one direction on entry, zero when stationary, deflection in the opposite direction on exit. Explicitly link this to the AQA statement: an induced current is only produced when there is a change in the magnetic field.
Stage 3 — Lenz’s Law: the opposing field (5 min) Toggle the 🏷 Labels on. Draw students’ attention to the large arrow inside the coil and the ⊗ / ⊙ symbols. Explain: “⊗ means the field is going away from you — into the coil. ⊙ means it is coming toward you.”
Ask: “When the N pole enters, the opposing field is ⊗ — pointing away from the approaching magnet. What does that tell you about which pole the coil is acting as?” Target: the coil end nearest the magnet becomes a N pole, repelling the incoming magnet. This is the mechanical consequence of Lenz’s Law — the induced current always opposes the change that caused it.
Stage 4 — Speed investigation (5 min) Students predict: “What happens to the galvanometer deflection if we move the magnet faster?” Then increase the speed slider and observe. Target: larger EMF (greater deflection) with faster motion — directly supporting Faraday’s Law that EMF is proportional to the rate of change of flux.
Stage 5 — Written explanation (5 min) Students write a four-sentence GCSE mark-scheme answer to: “Explain why a current flows in the coil when the magnet moves, and why the current reverses when the magnet is pulled out.”
Use the five step-chips as a writing frame when labels are on: Magnet moves → Flux changes → EMF induced → Current flows → Opposing field created.
Adaptation notes
- For lower-confidence learners: leave labels on throughout and use the step chips as sentence starters
- For higher ability: ask why the EMF waveform shows two peaks per full in-out cycle, and why there is a zero crossing in the middle — link to flux being at maximum (not changing) when the magnet is centred
- For SEND learners: use extra-slow mode and the reading ruler; the slider gives physical control that helps students connect cause and effect at their own pace; mute sound if the auditory channel is distracting