Oersted's discovery of electromagnetism, 1820. 19th-century illustration of Danish chemist and physicist Hans Christian Oersted (1777-1851) discovering electromagnetism, magnetism produced by an electric charge in motion. This discovery took place during a lecture on 21 April 1820. Oersted observed a compass needle being deflected as a nearby electric battery was switched on and off. For this discovery, Oersted was awarded the 1820 Copley Medal from the Royal Society. Artwork published in 1867.