Which Danish physicist discovered the phenomenon of electromagnetism in 1820?

Hans Christian Ørsted was the Danish physicist who discovered electromagnetism in 1820.

During a lecture in Copenhagen, Ørsted observed that an electric current in a wire could deflect a nearby compass needle. The experiment showed a direct connection between electricity and magnetism, which had previously been treated as separate phenomena.

Ørsted’s observation quickly influenced scientists including André-Marie Ampère and Michael Faraday. The discovery became a foundation of electromagnetic theory and modern electrical technology. The cgs unit of magnetic field strength, the oersted, was later named after him, and the Danish spelling of his surname is often written Oersted in English contexts.