Pöörisvooludeks

Pöörisvooludeks, also known as eddy currents, are electrical currents induced within bulk pieces of conductive material, such as aluminum or copper, whenever they are exposed to a changing magnetic field. This phenomenon was discovered by French physicist Léon Foucault in 1851, and it is a direct consequence of Faraday's law of induction.

When a conductor moves through a magnetic field, or when the magnetic field strength changes around a stationary conductor, the magnetic flux through the conductor changes. This change in magnetic flux induces an electromotive force (EMF) according to Faraday's law. Because the conductor is a continuous material, this induced EMF drives currents within the material itself. These currents circulate in closed loops, forming the characteristic whirlpool-like patterns that give them their name.

The direction of these induced currents is governed by Lenz's law, which states that the induced current will flow in a direction that opposes the change in magnetic flux that produced it. This opposition manifests as a braking force, often referred to as magnetic drag or eddy current braking.

Eddy currents can be both beneficial and detrimental. In applications like induction furnaces, eddy currents are intentionally generated to heat materials. They are also utilized in eddy current brakes for trains and other vehicles, and in metal detectors to identify conductive objects. However, in transformers and other electrical machinery, eddy currents can cause significant energy losses due to resistive heating (Joule heating), and steps are often taken to minimize them, such as laminating the conductive cores to increase electrical resistance between adjacent current loops.