Eddy current

An eddy current is a circulating electric current induced within a conductor by a changing magnetic field or motion through a magnetic field. Its loops generate magnetic fields that oppose the change producing them.

Faraday's law of induction: A law stating that changing magnetic flux through a circuit induces an electromotive force. Changing magnetic flux provides the electromotive force that drives eddy currents.
Eddy-current brake: A brake that uses induced currents and their opposing magnetic fields to slow a moving conductor without contact. It turns eddy-current drag into controlled braking force.
Hysteresis loss: Energy dissipated when a magnetic material is repeatedly magnetized and demagnetized. It is another source of core heating, distinct from resistive eddy-current loss.
Léon Foucault: A French physicist known for experiments including the pendulum demonstration of Earth’s rotation and studies of induced currents. His name became attached to eddy currents in several languages.
Transformer core loss: Energy dissipated in a transformer’s magnetic core through hysteresis and induced currents. Eddy-current heating is one component of this operating loss.
Lenz's law: A law stating that an induced current flows in a direction whose magnetic field opposes the change that produced it. It determines the direction of an eddy current’s magnetic response.
Induction heating: A process that heats an electrically conductive material using currents induced by an alternating magnetic field. Eddy-current resistance converts electromagnetic energy into heat.
Magnetic hysteresis: The dependence of a magnetic material’s magnetization on its previous magnetic history. Its lag causes losses without requiring circulating currents in the material.
Arago's rotations: The unexpected rotation of a suspended copper disk near a moving magnet, observed by François Arago in 1824. The effect was an early demonstration of magnetic induction producing mechanical drag.
Electromagnetic braking: Braking that uses electromagnetic forces to oppose motion and dissipate or recover kinetic energy. Eddy currents provide a common contactless means of electromagnetic braking.

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