American physicist (1855–1938)
Hall was born in Great Falls, Maine, and educated at Johns Hopkins University, Baltimore, where he received his PhD in 1880. After a year in Europe he joined the Harvard faculty and was appointed professor of physics in 1895, a post he held until his retirement in 1921.
While working for his thesis, Hall began to consider a problem first posed by Maxwell concerning the force on a conductor carrying a current in a magnetic field. Does the force act on the conductor or the current? Hall argued that if the current was affected by the magnetic field then there should be “a state of stress…the electricity passing toward one side of the wire.” Hall used a thin gold foil and in 1879 detected for the first time an electric potential acting perpendicularly to both the current and the magnetic field. The effect has since been known as the Hall effect. A simple interpretation is that the charge carriers moving along the conductor experience a transverse force and tend to drift to one side. The sign of the Hall voltage gives information on whether the charge carriers are positive or negative.
Other so-called galvanomagnetic effects were later discovered by Walter Nernst and others. Hall spent much of his later life attempting to measure the various effects as exactly as possible.
More than a century after its discovery Klaus von Klitzing was awarded the 1985 Nobel Prize for physics for his work on the Hall effect.
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