who established the close connection between electricity and magnetism
Hans Christian Ørsted Hans Christian Ørsted (/ˈɜːrstɛd/;[2] Danish: [hans kʁæsdjan ˈɶɐ̯sdɛð]; often rendered Oersted in English; 14 August 1777 – 9 March 1851) was a Danish physicist and chemist who discovered that electric currents create magnetic fields, which was the first connection found between electricity and magnetism. He is still known today for Oersted's Law and the oersted (Oe), the cgs unit of magnetic H-field strength, is named after him. . He shaped post-Kantian philosophy and advances in science throughout the late 19th century.[3]
Joseph Henry Joseph Henry (December 17, 1797 – May 13, 1878) was an American scientist who served as the first Secretary of the Smithsonian Institution. He was the secretary for the National Institute for the Promotion of Science, a precursor of the Smithsonian Institution.[1] He was highly regarded during his lifetime. While building electromagnets, Henry discovered the electromagnetic phenomenon of self-inductance. He also discovered mutual inductance independently of Michael Faraday, though Faraday was the first to make the discovery and publish his results.[2][3][4] Henry developed the electromagnet into a practical device. He invented a precursor to the electric doorbell (specifically a bell that could be rung at a distance via an electric wire, 1831)[5] and electric relay (1835).[6] The SI unit of inductance, the henry, is named in his honor. Henry's work on the electromagnetic relay was the basis of the practical electrical telegraph, invented by Samuel F. B. Morse and Sir Charles Wheatstone, separately.