Hall effect

Hall effect is the creation of an electric voltage transversely in a conductor through which an electric current flows longitudinally, which is deflected magnetic field perpendicular to the direction of the current.

Hall's phenomenon was discovered in 1879 by a then twenty-four-year-old student Edwin Herbert Hall. He placed a thin gold sheet in a homogeneous magnetic field perpendicular to its field lines. He then let an electric current pass through the plastic. The magnetic field was deflecting electrons moving through the conductor from a straight path and causing their uneven distribution across the conductor. Due to the action of the magnetic field, there was an excess of them on one side of the plate, and a lack of them on the opposite side. This caused a measurable tension between the two sides of the plate. This "Hall voltage" is directly proportional to the magnitude (magnetic induction) of the magnetic field at constant current.

A device using the Hall effect to measure magnetic induction is called a 'Hall probe. While Hall worked with metal foils in which there is a large concentration of conduction electrons, today's Hall probes mostly contain a slice of semiconductor with a relatively small concentration of charge carriers, which makes the phenomenon easier to measure. Hall probes are widely used in everyday practice. E.g. in automotive engines, Hall sensors (top) sense the position of the crankshaft and enable accurate mixture ignition timing.

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Lorentz force

Source

 * REICHL, J.. Encyklopedie fyziky [online]. [cit. 2013-11-29]. http://fyzika.jreichl.com/main.article/view/294-halluv-jev