Tesla devised a highly efficient induction motor, which utilized alternating current, or AC, electricity—where current switches direction multiple times per second. The invention made the transmission of electricity on large scales more efficient and cost-effective than direct current, or DC, technologies—where current doesn’t switch direction.
During The Current War, Thomas Edison argued that AC was dangerous and DC, which he had heavily invested in, should be used instead. However, once the 1893 Chicago World's Fair was electrified by AC, the war was won by Tesla and George Westinghouse, who had purchased Tesla's patents for AC power generation, transmission, and application.
Beyond pioneering the technology for the electric grid, Tesla patented the Tesla coil, a device that would serve as the foundation for wireless transmission technologies.