Michael Faraday discovered electromagnetic induction
On this day · 29 August 1831
With two coils wound on an iron ring, Faraday caught a needle twitching and uncovered the principle behind every electric generator.
On August 29, 1831, working in the basement laboratory of the Royal Institution in London, Michael Faraday carried out the experiment that revealed electromagnetic induction. He wound two separate coils of insulated wire around opposite sides of an iron ring, connecting one to a battery and the other to a galvanometer.
When he switched the battery on, the galvanometer needle gave a brief twitch, then settled; switching off produced another flick in the opposite direction. Faraday grasped that only a changing magnetic field, not a steady one, induced a current in the second coil.
The ring was, in effect, the first electric transformer, and it survives in the Royal Institution’s collection.
The insight underpins generators, transformers, and motors, and was later cast into mathematical form by James Clerk Maxwell as Faraday’s law. A changing magnetic field, Faraday had shown, can summon electricity from a wire that touches no battery at all.
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