Electricity surrounds us not only in production but also in everyday life.A person may not even know that such eddy currents, but with the work they performed, face daily.For example, people have long used to turn on the light touch of a button switch, without thinking about the processes taking place at the same time.That is what happened in this case.Therefore, to understand what is hidden under the term "eddy eddy currents" and to determine the mechanism of their occurrence, it is necessary to recall the characteristics of an electric current.But first, to answer the question "why Foucault?"
first eddy currents have been mentioned in the writings of the French physicist Arago DF He drew attention to the strange behavior of the copper disc, which was located on a rotating magnetized needle.Without apparent reason, the disc begins to rotate with the rotation arrows.At that time (1824) explain this behavior could not yet, so the phenomenon was called "the phenomenon of Arago."A few years later, another scientist - Michael Faraday, using the phenomenon of Arago's discovery of the law of electromagnetic induction, came to the conclusion that in this case the motion of the disk can be easily explained in terms of the Act.Under the proposed explanation of the rotating magnetic field acts on the atoms of the conductor (copper disk), and causes a directional motion of charged (polarized) particles in the structure.One of the characteristics of electric current is that there is always a conductor around a magnetic field.It is not hard to guess that the eddy currents create their field that interacts with the main, they are generating.The word "vortex" describes the method of distribution of currents in the conductor: their directions are electrically connected.Based on the works of Arago and Faraday seriously eddy currents studied physics Foucault.Hence, the resulting name.
These currents are not much different from the induction produced by generators.If there is a whirling magnetic field (alternating rotating) and located next to the conductor, it is due to the action of electromagnetic fields induced currents.The larger and more massive than the conductor, the higher the current value is generated by currents.Moreover, eddy currents always create a magnetic field that opposes the change in flux.With the growth of the root causes of the current-directed counter EMF increases and with a decrease, on the contrary, the field eddy currents support the main stream.The above should be the law of Lenz.
Definitely can not say, useful or harmful eddy currents in some cases they are viewed as parasitic and use different technological solutions to reduce them in others, on the contrary, demand are the very properties of these currents.Each inquisitive boy once deciphered thrown transformer.The core (the basis on which the windings are wound) is not always made whole, and recruited a large number of thin plates, electrical steel (it is called a laminated).All components of the design of the plate covered with an insulating varnish and baked for a reliable connection.Sometimes the core shrinks further isolated pin.Such a complication of the construction stimulated: it is necessary to substantially reduce the eddy currents in the core.Indeed, as has been said, the less massive conductor, the high resistance to electric current it possesses.
In other cases, some of the properties of the eddy currents are demanded.For example, the work of induction furnaces is based on the heating effect of the massive conductor eddy currents induced by a special generator.Furthermore, they are used to determine the presence of imperceptible deffektov in the metal structure.
