gutenberg_org, Serbian inventor, electrical engineer, mechanical engineer, & futurist Nikola Tesla died #OTD in 1943. He discovered & patented the rotating magnetic field, the basis of most alternating-current machinery. He also developed the 3-phase system of electric power transmission. In 1891 he invented the Tesla coil, an induction coil widely used in radio technology. He conducted a range of experiments with mechanical oscillators/generators, electrical discharge tubes, & early X-ray imaging.