🧲 Faraday's Law — Electromagnetic Induction
Drag the magnet left and right through the coil. The induced EMF obeys ε = −N dΦ/dt; the faster you move, the stronger the induced current. The current direction follows Lenz's law.
Magnet
Coil
Motion Mode
Induced EMF
Magnetic Flux Φ
Current Direction
What It Demonstrates
Faraday's Law (1831) states that a changing magnetic flux through a closed loop induces an electromotive force (EMF): ε = −N dΦ/dt. The negative sign reflects Lenz's law: the induced current opposes the change that created it. This principle underlies every electric generator, transformer, and induction motor ever built.
How to Use
- Drag the magnet left and right across the coil — watch ε spike as you move past the center
- Increase Turns N to amplify the EMF proportionally
- Increase B₀ (stronger magnet) to get larger flux and therefore larger ε
- Use Auto mode for continuous oscillation. The EMF is proportional to velocity (sinusoidal motion → sinusoidal EMF)
- Click Flip Poles to swap N↔S and observe the EMF reversal
Did You Know?
Faraday had no mathematical training yet discovered the foundational law of electromagnetism experimentally. Maxwell later wrote it as one of the four Maxwell equations: ∇ × E = −∂B/∂t. This single equation explains how your phone charges wirelessly, how MRI machines work, and why electric guitars make sound.