Loops of electric current induced within conductors by a changing magnetic field
For the comic-book series, see Eddy Current (comics). For the Australian rock band, see Eddy Current Suppression Ring.
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In electromagnetism, an eddy current (also called Foucault's current) is a loop of electric current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction or by the relative motion of a conductor in a magnetic field. Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. They can be induced within nearby stationary conductors by a time-varying magnetic field created by an AC electromagnet or transformer, for example, or by relative motion between a magnet and a nearby conductor. The magnitude of the current in a given loop is proportional to the strength of the magnetic field, the area of the loop, and the rate of change of flux, and inversely proportional to the resistivity of the material. When graphed, these circular currents within a piece of metal look vaguely like eddies or whirlpools in a liquid.
By Lenz's law, an eddy current creates a magnetic field that opposes the change in the magnetic field that created it, and thus eddy currents react back on the source of the magnetic field. For example, a nearby conductive surface will exert a drag force on a moving magnet that opposes its motion, due to eddy currents induced in the surface by the moving magnetic field. This effect is employed in eddy current brakes which are used to stop rotating power tools quickly when they are turned off. The current flowing through the resistance of the conductor also dissipates energy as heat in the material. Thus eddy currents are a cause of energy loss in alternating current (AC) inductors, transformers, electric motors and generators, and other AC machinery, requiring special construction such as laminated magnetic cores or ferrite cores to minimize them. Eddy currents are also used to heat objects in induction heating furnaces and equipment, and to detect cracks and flaws in metal parts using eddy-current testing instruments.
In electromagnetism, an eddycurrent (also called Foucault's current) is a loop of electric current induced within conductors by a changing magnetic field...
An eddycurrent brake, also known as an induction brake, Faraday brake, electric brake or electric retarder, is a device used to slow or stop a moving...
An eddycurrent separator (ECS) is a machine that uses a powerful magnetic field to separate non-ferrous metals from an input waste or ore stream. The...
EddyCurrent Suppression Ring (sometimes seen as ECSR) are an Australian rock band formed in 2003. By 2004 their line-up was Daniel Young p.k.a. Danny...
needed] Eddycurrents are electric currents that occur in conductors exposed to changing magnetic fields.[citation needed] Similarly, electric currents occur...
magnetic field, will have circular currents induced within them by induction, called eddycurrents. Eddycurrents flow in closed loops in planes perpendicular...
1885. In early 1885, the three engineers also eliminated the problem of eddycurrent losses with the invention of the lamination of electromagnetic cores...
magnetizing current losses, consisting of Hysteresis losses due to nonlinear magnetic effects in the transformer core, and Eddycurrent losses due to...
common viscous damper, the eddycurrent damper produces a resistive force proportional to velocity. A common use of the eddycurrent damper is in balance scales...
and Scottish families Eddy (given name), male given name Eddy (fluid dynamics), the swirling of a fluid and the reverse current created when the fluid...
Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through...
account. In alternating current (AC) devices they cause energy losses, called core losses, due to hysteresis and eddycurrents in applications such as...
manually controlled or determined by a computer. Most systems employ eddycurrent, oil hydraulic, or DC motor produced loads because of their linear and...
electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. The current density vector...
inventor Otto Schultze patented his version (which, like Belušić's, ran on eddycurrents) on 7 October 1902. Many speedometers use a rotating flexible cable...
frequency current is higher than its resistance to direct current because of skin effect. Due to induced eddycurrents, radio frequency alternating current does...
the eddycurrent effect. It is also called electromagnetic induction tomography, electromagnetic tomography (EMT), eddycurrent tomography, and eddy current...
(which is a function of field current), either armature voltage or field current can be used to control speed. An eddycurrent drive (sometimes called a "Dynamatic...
super multiple of the supply frequency. Other types of motors include eddycurrent motors, and AC and DC mechanically commutated machines in which speed...
electric current passing through it. The resulting oscillating magnetic field induces an electrical current in the vessel. This large eddycurrent flowing...
presence of current harmonics in a transformer also result in larger eddycurrents in the magnetic core of the transformer. Eddycurrent losses generally...
charge.[citation needed] The old SI definition for volt used power and current; starting in 1990, the quantum Hall and Josephson effect were used, and...
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