Electricity surrounds us not only atproduction, but also in everyday life. A person may not even know what vortex currents are, but with the work they do, they face daily. For example, people have long been accustomed to turning on the light by simply pressing the button of the switch, without thinking about the processes taking place in this process. And it happened in this case. Therefore, in order to understand what is hidden under the term "Foucault eddy currents" and to determine the mechanism of their origin, it is necessary to recall the properties of the electric current. But first we will answer the question "why Foucault"?
For the first time eddy currents were mentioned in the worksFrench physicist Arago DF. He drew attention to the strange behavior of the copper disk, above which was a rotating magnetized arrow. For no apparent reason, the disc began to rotate with the rotation of the arrow. At that time (1824), such behavior could not be explained, therefore the phenomenon was called "Arago phenomenon". A few years later, another scientist, M. Faraday, having applied the phenomenon of electromagnetic induction to the phenomenon of Arago, came to the conclusion that in this case the movement of a disk is easy to explain from the point of view of the law mentioned. According to the proposed explanation, the rotating magnetic field acts on the atoms of the conductor (copper disk) and causes the appearance of directed motion of charged (polarized) particles in the structure. One of the properties of electric current is that there is always a magnetic field around the conductor. It is not difficult to guess that eddy currents also create their own field, which interacts with the ground, generating them. The word "vortex" characterizes the method of propagation of such currents in a conductor: their directions are looped. Based on the work of Arago and Faraday, Foucault's physicist seriously studied eddy currents. Hence the name received.
These currents differ little from induction,produced by generators. If there is a vortex magnetic field (alternating, rotating) and a nearby conductor, then currents are induced in it by the action of electromagnetic fields. The larger and more massive the conductor, the higher the effective value of the currents that are created. And, eddy currents always create such a magnetic field, which resists the change in flow. As the current-root cause increases, the EMF directed oppositely, and with decreasing, on the contrary, the field of eddy currents maintains the main current. The foregoing follows from the Lenz law.
Definitely can not be said useful or harmfuleddy currents: in some cases they are regarded as parasitic and various technological solutions are used to reduce them; in others, on the other hand, the properties of such currents themselves are in demand. Each curious boy once parceled the discarded transformer. The core (the base on which windings are wound) is always not made solid, but is recruited from a large number of thin plates of electrical steel (it is called a charge). All components of the construction of the plate are covered with an insulating lacquer and baked for a reliable connection. Sometimes the core is further tightened by an isolated hairpin. This complication of the design is forced: it is necessary to substantially reduce the eddy currents in the core. After all, as has already been said, the less massive the conductor, the greater the resistance to the electric current it possesses.
In other cases, certain properties of the vortexcurrents are in demand. For example, the work of induction steelmaking furnaces is based on heating a massive conductor of the action of eddy currents induced by a special generator. In addition, they are used to determine the presence of imperceptible defects in the structure of the metal.
