Electromagnetic Induction and Lenz's Law: Interactive Simulator
An interactive simulator for Faraday's and Lenz's laws: drag a bar magnet through a solenoid and see Φ–t and ε–t graphs, the induced current's direction and poles, and the force on the magnet. Practise Lenz's law in five steps, and analyse a rod on rails: ε = BLv, F = B²L²v/R, coasting and terminal velocity, and where the energy goes.
About this simulation
- What
- An interactive Physics simulation of Electromagnetic Induction and Lenz's Law: Interactive Simulator.
- Who
- Designed for AP, IB, and A‑Level Physics students.
- How
- Runs in any modern browser — drag, adjust, and explore in real time.
Updated 2026-10-11
Key Concepts
Faraday's law
The induced emf equals the rate of change of flux linkage: ε = −N dΦ/dt. Faster changes and more turns give a larger emf; no change, no emf.
Lenz's law
The induced current's own field opposes the change in flux that causes it: an approaching magnet is repelled, a departing one attracted.
Moving conductor
A rod of length L moving at v across a field B has ε = BLv. With a closed circuit the current gives a force BIL on the rod that opposes its motion.
Energy
Induction never gives energy for free: the work done against the magnetic force becomes the electrical energy dissipated as heat, I²R.
What This Electromagnetic Induction Simulator Teaches
Electromagnetic induction is in AQA A-level Physics (Faraday's and Lenz's laws), AP Physics C: E&M and the Chinese textbook (人教版选择性必修二 第二章). This simulator covers the three situations exams use: a magnet and a coil, Lenz's law reasoning, and a rod sliding on rails.
With the magnet and coil you see the flux and the emf graphed together, so that ε = −N dΦ/dt becomes visible: the emf follows the gradient of the flux graph. The induced current, the coil's poles and the force on the magnet show Lenz's law at work, and opening the switch shows why the current — not the emf — produces the force.
The Lenz's law stage asks you to predict each step before watching, with answers worked out by the model itself. The sliding rod links induction to mechanics and energy: ε = BLv, the braking force B²L²v/R, coasting with a time constant, terminal speed, and the work done turning into heat.
