Electromagnetic Induction — Class 12 Physics

A changing magnetic flux through a circuit induces an emf—the heart of electromagnetic induction. Magnetic flux is . Faraday's law states that the induced emf equals the rate of change of flux, , while Lenz's law, expressed by the negative sign, ensures the induced current opposes the change producing it—a statement of energy conservation. A conductor of length moving with speed across a field generates a motional emf . Changing fluxes also drive eddy currents in bulk conductors, used in braking and induction heating but minimised by lamination in transformers. Self-inductance opposes changes in a coil's own current, with emf and stored energy . Mutual inductance couples two coils, the basis of the transformer. An AC generator converts mechanical energy into electrical energy by rotating a coil in a field, producing a sinusoidal emf , embodying the link between motion, magnetism and electricity.