Faraday's Law of Induction

Discover how a changing magnetic field induces a current in a coil.

The Concept: Magnetic Flux & Lenz's Law

A changing magnetic flux (the number of B-field lines through the coil) induces a voltage (EMF) and a current.

Lenz's Law: The induced current creates its own magnetic field (in green) that opposes the change in flux. If flux is increasing, the induced field fights it. If flux is decreasing, the induced field tries to boost it.

How to Use the Lab

Drag the bar magnet in and out of the coil of wire.
Watch the light bulb: it glows when a current is induced.
Observe the yellow particles to see the direction of the induced current.
Notice the faint green induced B-Field from the coil that opposes the change.
The "Live Analysis" panel shows the real-time calculations.

Controls

Number of Loops (N): 2

Magnet Strength: 1.0 T

Faraday's Law

$\mathcal{E} = -N \frac{d\Phi_B}{dt}$

Live Analysis

Magnetic Flux ($\\Phi_B$):

- Wb

Change in Flux ($d\\Phi_B/dt$):

- Wb/s

Induced EMF ($\\mathcal{E}$):

- V