pyörivirrat

Pyörivirrat, also known as eddy currents, are electrical currents induced within conductors by a changing magnetic field. This phenomenon was first described by French physicist Léon Foucault in 1851, leading to the alternative name Foucault currents.

When a conductor, such as a piece of metal, is placed in a varying magnetic field, the magnetic flux through the conductor changes. According to Faraday's law of induction, this change in flux induces an electromotive force (EMF) within the conductor. Since the conductor is a closed circuit, this EMF drives electrical currents. These currents flow in localized, circulating paths within the conductor, resembling eddies in a fluid, hence the name.

The magnitude and direction of pyörivirrat depend on the rate of change of the magnetic field and the properties of the conductor, such as its resistivity and permeability. Higher conductivity and faster magnetic field changes lead to stronger eddy currents. The induced currents generate heat due to the conductor's resistance, a phenomenon described by Joule heating.

Pyörivirrat have both beneficial and detrimental applications. In electromagnetic braking systems, eddy currents are used to slow down moving objects by generating a retarding force. They are also utilized in induction heating, where the heat generated by eddy currents is used to melt or temper metals. In electrical devices like transformers and motors, eddy currents can cause energy loss, leading to reduced efficiency. To minimize these losses, magnetic cores are often made of laminated materials, which increase the electrical resistance between layers and thus reduce the magnitude of the eddy currents.