The Hall effect produces a voltage across a conductor carrying current in a magnetic field.
When charge carriers move through a conductor or semiconductor and a magnetic field is applied perpendicular to their motion, the Lorentz force pushes carriers toward one side. This charge separation creates a transverse voltage called the Hall voltage. Its size and polarity depend on the current, magnetic field, material, and carrier properties.
Edwin Hall discovered the effect in 1879 while studying thin metal plates. The effect became especially useful in semiconductors, where it can reveal whether the main carriers are electrons or positive holes and can help determine carrier density.
Hall sensors now measure magnetic fields, detect position and rotation, and switch electrical systems without mechanical contacts. The Hall effect should not be confused with the Seebeck effect, which produces a voltage from a temperature difference.