Oersted's experiment
Oersted, a Danish physicist, accidentally discovered the occurrence of a magnetic field around a current-carrying wire. Oersted said that he was surprised to see the compass's magnetic needle placed next to the wire rotate while experiment to show students the phenomenon that the wire heats up when an electric current flows through it.
Oersted experimented with this phenomenon several times, revealing a close relationship between electrical and magnetic phenomena. Since Oersted's discovery, the study of the interaction between electricity and magnetism has been actively conducted, and today, electromagnetism integrating the two phenomena has been completed.