Electromagnetic Induction

See how changing magnetic flux generates EMF — Faraday's and Lenz's Laws in action

Faraday's Law states that the induced EMF in a coil equals the negative rate of change of magnetic flux through it: ε = −N dΦ/dt. For a coil of N turns and area A rotating at angular velocity ω in field B, the flux varies as Φ = BA cos(ωt), giving a peak EMF of NBAω. Lenz's Law determines the polarity of the induced EMF: it always opposes the change that caused it, which is a direct statement of energy conservation.