Edwin Hall
American physicist (1855–1938)
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Through Electromagnetism, Gold and Glass
Education and career
Born in Gorham, Maine, Hall did his undergraduate work at Bowdoin College, Brunswick, Maine, graduating in 1875. He was the Principal of Gould Academy (1875–76) and the Principal of Brunswick High School (1876–77). He did his graduate schooling and research, and earned his Ph.D. in 1880 at the Johns Hopkins University where his seminal experiments were performed.
Hall was appointed a professor of physics at Harvard University in 1895, and succeeded John Trowbridge to the Rumford Chair of Physics in 1914. During the 1919 Boston police strike, Hall briefly volunteered as a strikebreaking police officer. After returning to the Physics Department, Hall retired in 1921 and died in Cambridge, Massachusetts, in 1938.
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Hall effect
The Hall effect was discovered by Hall in 1879, while working on his doctoral thesis in physics under the supervision of Henry Augustus Rowland. Hall's experiments in electromagnetics consisted of exposing thin gold leaf (and, later, using various other materials) on a glass plate and tapping off the gold leaf at points down its length. The effect is a potential difference (Hall voltage) on opposite sides of a thin sheet of conducting or semiconducting material (the Hall element) through which an electric current is flowing. This was created by a magnetic field applied perpendicular to the Hall element. The ratio of the voltage created to the amount of current is known as the Hall resistance and is a characteristic of the material in the element. In 1880, Hall's experimentation was published as a doctoral thesis in the American Journal of Science and in the Philosophical Magazine.
Hall-effect sensors use his Hall effect to detect the magnetic field. Hundreds of millions are sold every year and are present in a large number of devices, including high-efficiency electric propulsion systems on spacecraft.
In the presence of large magnetic field strength and low temperature, one can observe the quantum Hall effect, the quantization of the Hall resistance. In 1990, it became a calibration standard for electrical resistance due to its low uncertainty (see Quantum Hall effect § Applications).