What Is Electromagnetic Induction?

In 1831, Michael Faraday discovered that a changing magnetic field through a loop of wire induces an electromotive force (voltage) and current in the wire. The key is "changing": a static magnetic field produces no current. This can happen by moving a magnet near a coil, moving the coil in a magnetic field, or changing the strength of the magnetic field over time. Faraday law states that the induced EMF is proportional to the rate of change of magnetic flux through the circuit. This principle is the foundation of modern electricity generation: in a generator or dynamo, a coil of wire rotates in a magnetic field (or a magnet rotates within a coil), continuously changing the magnetic flux and producing alternating current. Transformers use electromagnetic induction to step voltage up or down for efficient power transmission. Wireless charging pads, induction cooktops, and electromagnetic braking all rely on the same principle.