What Is Eddy Current?
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Eddy currents (also called Foucault's currents) are loops of electrical currentinduced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction. 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.
What is the principle of eddy current?
The eddy current method is based on the principle of generating circular electrical currents (eddy currents) in a conductive material. This is achieved by the use of a coil connected to an alternating current generator driving an alternating magnetic field (primaryfield).
What is eddy current and how it is produced?
Eddy currents are currents which circulate in conductors like swirling eddies in a stream. They are induced by changing magnetic fields and flow in closed loops, perpendicular to the plane of the magnetic field. ... Like any currentflowing through a conductor, an eddy currentwill produce its own magnetic field.
What are eddy currents and its applications?
The heating effect of the eddy current is used for melting metal in an induction furnace. Eddy currents of large magnitude are produced field. The changes in the magnetic field are so rapid that very large eddy currents are generated and heat produced is sufficient to melt quickly.
Why eddy current is called Eddy?
Eddy currents are named so because thecurrent looks like eddies or whirlpools. When a conductor is placed in the changing magnetic field, the induced current in the conductor is termed as Eddy currents.
Are eddy currents AC or DC?
Eddy currents, however, have no direction. They just circulate whenever a conducting material of large enough cross section is available. ... In an AC circuit, the current oscillates between the source and load alternatively at the system frequency. In a DCcircuit, the current always flows in the same direction.
What are the advantages of eddy current?
The advantages of eddy current testing are: Sensitivity to surface defects. Able to detect defects of 0.5mm in length under favourable conditions. Can detect through several layers.
How can eddy current be prevented?
In order to reduce the eddy current loss, the resistance of the core should be increased. In devices like transformers, the core is made up of thin sheets of steel, each lamination being insulated from others by a thin layer of varnish. As the laminations are thin, they will have relatively high resistance.
What causes an eddy?
General patterns of ocean flow are called currents. Sometimes theses currents can pinch off sections and create circular currents of water called an eddy. ... The swirling motion of eddies in the ocean cause nutrients that are normally found in colder, deeper waters to come to the surface.
What is difference between eddy current and induced current?
Definition: Eddy currents refer to loopscurrents induced within large bodies of conductors, as a result of a changing magnetic field across it. Induced currentstypically refer to currents induced in coils connected to a closed circuit.
Does Eddy Current give shock?
What's an eddy current? We get an electricshock because the current flows through our body to reach the ground. ... Even when a powerful electrical shock was applied, this gas would not react with oxygen but would give off a reddish-pinkish glow.
What is eddy current used for?
Eddy currents in conductors of non-zero resistivity generate heat as well as electromagnetic forces. The heat can be used for induction heating. The electromagnetic forces can be used for levitation, creating movement, or to give a strong braking effect.
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