Discoverer of Self-Induction and Co-discoverer of Electromagnetism.
- In 1829, Henry demonstrated that a current induced in a coil would induce a corresponding current in a nearby coil.
- In 1830, Joseph Henry discovered self-induction. He showed that a changing current in a wire induces an electromotive force (EMF) in the same wire.
- Henry also discovered that a current-carrying wire produces a magnetic field. This discovery was made independently of Michael Faraday, who also discovered it around the same time.
- Henry's work on electromagnetism was essential to the development of the telegraph, the telephone, and other electrical devices.
- He was the first Secretary of the Smithsonian Institution.