What happens to the induced EMF when you double the number of coil turns?

Ε = N × dΦ/dt — doubling N doubles ε.

The magnet is stationary inside the coil. Why is there no induced EMF?

Faraday's Law requires dΦ/dt ≠ 0 — flux must be changing.

Why does Lenz's Law mean the induced current always opposes the motion causing it?

Energy conservation: creating current from nothing would violate it.

Pro 🔒~20 min

Faraday's Electromagnetic Lab

Discover electromagnetic induction with a magnet and coil

How it works

Faraday's Law states that a changing magnetic flux through a coil induces an electromotive force (EMF) proportional to the rate of change and the number of turns. Lenz's Law determines the direction: the induced current creates a magnetic field opposing the change that caused it. This principle underlies all electric generators, transformers, and induction cooktops.

Upgrade to Pro to access this experiment

Step-by-step

Drag the magnet toward and through the coil.
The voltmeter shows induced EMF.
Move the magnet faster or use more coil turns to increase the induced voltage.
Reverse direction to reverse the current.
Connect a light bulb to the coil and see it glow.

Key formulas

$\mathcal{E} = -N\frac{d\Phi_B}{dt}$ Faraday's Law of Induction
$\Phi_B = B \cdot A \cdot \cos\theta$ Magnetic flux

Frequently asked questions

What happens to the induced EMF when you double the number of coil turns?: Ε = N × dΦ/dt — doubling N doubles ε.
The magnet is stationary inside the coil. Why is there no induced EMF?: Faraday's Law requires dΦ/dt ≠ 0 — flux must be changing.
Why does Lenz's Law mean the induced current always opposes the motion causing it?: Energy conservation: creating current from nothing would violate it.