Nikola Tesla · Wireless power
In the 1890s and 1900s, Nikola Tesla pursued a bold idea: electricity could travel without wires, using resonant coils and — he believed — the Earth itself as a conductor. Some of it worked brilliantly in the lab. His grandest version, a tower meant to power the world, was never finished. Explore both below.
Tesla's most practical wireless power idea, still used today in wireless phone chargers: two coils tuned to the exact same frequency exchange energy efficiently through their magnetic fields — even with no wire between them. Detune them even slightly, and the transfer collapses.
A Tesla coil is a resonant transformer: a primary coil at the base steps voltage up dramatically through a much longer secondary coil, producing extremely high-voltage, high-frequency AC — enough to arc through air as a visible spark.
Tesla's most ambitious vision: a tower on Long Island that would use the Earth and upper atmosphere to relay electricity — and information — to any point on the globe. Investor J.P. Morgan pulled funding in 1904 once he realized the system couldn't be metered per customer, and the unfinished tower was demolished in 1917. The idea below is Tesla's concept, not a working system.
Historical note: Wardenclyffe never transmitted usable power to anyone. This diagram illustrates the theory Tesla was chasing, not a result he achieved.
Key moments in Tesla's pursuit of wireless power.