Electric motor

The electric motor emerged from a challenge issued as a joke. In 1820, Hans Christian Ørsted announced that electric current deflected a compass needle—proof that electricity and magnetism were related. Humphry Davy and William Hyde Wollaston tried to build a device that would use this effect to produce rotation and failed. Davy challenged his laboratory assistant, Michael Faraday, to try. On September 3, 1821, in the basement of the Royal Institution in London, Faraday demonstrated the first electromagnetic rotation—the ancestor of every electric motor that would follow.

The adjacent possible for the electric motor required the convergence of electrical science with mechanical engineering. Voltaic piles had been producing continuous electric current since 1800. Electromagnetism had been discovered just a year before Faraday's experiment. The conceptual insight—that a wire carrying current near a magnet would experience a force—was new enough that no one had yet figured out how to harness it for continuous motion.

Faraday's apparatus was elegantly simple. A free-hanging wire was dipped into a pool of mercury, which served as an electrical contact. A permanent magnet stood upright in the mercury. When current flowed through the wire, the electromagnetic force caused the wire to rotate continuously around the magnet. The device converted electrical energy into mechanical motion without human intervention. Faraday called the effect "electromagnetic rotation" and sent pocket-sized models to colleagues across Europe so they could witness the phenomenon themselves.

Peter Barlow refined the concept the following year with his Barlow's wheel, a copper disc rotating between the poles of a horseshoe magnet. These homopolar motors demonstrated the principle but remained laboratory curiosities—too weak and inefficient for practical work. The motors that would eventually power industry required decades of refinement: commutators to reverse current direction, wound coils to multiply the electromagnetic effect, and better magnetic materials.

The delay between demonstration and application illustrates a recurring pattern in invention. Faraday's 1821 motor proved that electricity could produce continuous rotation. The motors that drove the Second Industrial Revolution—powering factories, streetcars, and eventually everything from elevators to washing machines—didn't emerge until the 1870s and 1880s, when better dynamos could supply sufficient current and engineers had developed practical designs.

The electric motor and the electric generator are essentially the same device run in opposite directions. Current flowing into a motor produces rotation; rotation of a generator produces current. This reversibility, recognized early, meant that advances in one domain immediately transferred to the other. The path from Faraday's mercury-pool experiment to the motors that run modern civilization took decades of incremental improvement, but the fundamental insight—that electromagnetic forces could produce continuous motion—came from that September afternoon in 1821.