Joseph Henry

Joseph Henry (December 17 1797 – May 13 1878) was an American scientist. During his lifetime, he was considered the greatest American scientist since Benjamin Franklin. While building electromagnets, he discovered the electromagnetic phenomenon of self-inductance. He also discovered mutual inductance, independently of Faraday, but Faraday was the first to publish his results. His work on the electromagnetic relay was the basis of the electrical telegraph, jointly invented by Morse and Wheatstone.

At The Albany Academy

Joseph Henry excelled at his studies (so much so, that he would often be helping his teachers teach science) and, by 1826, he was appointed Professor of Mathematics and Natural Philosophy at The Albany Academy. Some of Henry's most important research was conducted in this new position. Joseph?s curiosity about terrestrial magnetism lead him to experiment with magnetism in general. He was the first to tightly coil insulated wire around a ferrous core to make an extremely powerful electromagnet, improving on William Sturgeon?s electromagnet, which used loosely coiled uninsulated wire. Using this technique, he built the most powerful electromagnet at the time, for Yale. He also showed that, when making an electromagnet using just two electrodes attached to a battery, it is best to wind several coils of wire in parallel, but, when using a set up with multiple batteries, there should be only one single, long coil used. The latter made the telegraph feasible.

Related Topics:
1826 - Albany Academy - Terrestrial magnetism - Magnetism - Electromagnet - William Sturgeon - Yale - Electrode - Telegraph

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He took what he had learned a step further and, in 1831, created one of the first machines to use electromagnetism for motion. This was the earliest ancestor of modern DC motor. It didn?t make use of rotating motion, but was merely an electromagnet perched on a pole, rocking back and forth. The rocking motion was caused by on of the two leads on both ends of the magnet rocker touching one of the two battery cells, causing a polarity change, and rocking the opposite direction until the other two leads hit the other battery.

Related Topics:
1831 - DC motor

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Here, he also discovered the property of self inductance. But, around the same time, a British scientist by the name of Michael Faraday had discovered it as well and was quicker to publish his results, becoming the officially recognized discoverer of the phenomenon.

Related Topics:
Self inductance - Michael Faraday

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