Hallwaarde

Hallwaarde is the Dutch term for the Hall voltage, the transverse electric potential that appears across a conductor or semiconductor when it carries an electric current in the presence of a magnetic field perpendicular to the current. The effect is named after Edwin Hall, who discovered it in 1879. The Hall voltage arises because charge carriers experience a Lorentz force that deflects them to one side of the material, creating a buildup of charge that opposes further deflection and establishes an equilibrium Hall field. The magnitude of the Hall voltage depends on the current, the magnetic field, the density and sign of charge carriers, and the geometry of the sample.

In simple models with a single type of charge carrier, the Hall coefficient R_H is defined by R_H = V_H d /(I B), where d is the distance across which the Hall voltage is measured. For many metals and doped semiconductors R_H ≈ 1/(n q), where n is carrier density and q is elementary charge. The Hall voltage is then V_H = (R_H I B)/d. The sign of V_H indicates whether carriers are predominantly electrons or holes.

Applications of Hallwaarde include the use of Hall effect sensors to measure magnetic fields, determine carrier density and mobility in materials, and support fundamental research in solid-state physics. Practical measurements require careful control of geometry, temperature, and material quality, since multi-carrier conduction and anisotropy can complicate interpretation.

See also: Hall effect; Hall coefficient; Hall probe; Semiconductor physics.