Eddy currents, also known as Foucault currents, are swirling currents that circulate throughout the volume of a material. These currents are induced by a changing magnetic field or by the motion of a conductor through a magnetic field. Eddy currents are commonly observed in conductive materials such as metals.

Eddy currents are a result of electromagnetic induction, which occurs when there is a relative motion between a conductor and a magnetic field. According to Faraday's law of electromagnetic induction, a changing magnetic field induces an electromotive force (EMF) in a conductor. This EMF causes a circulating current to flow in the conductor, resulting in the formation of eddy currents.

The key characteristics of eddy currents are as follows:

1. Circulation throughout the volume: Eddy currents circulate throughout the volume of a conductive material. They are not confined to a specific path or direction like a conventional electric current.

2. Similar to swirling eddies in a river: Eddy currents resemble the swirling eddies observed in a flowing river. They create circular patterns of current flow within the material, which dissipate energy in the form of heat.

3. Induced by changing magnetic fields: Eddy currents are induced by a changing magnetic field. When a magnetic field varies in strength or direction, it creates a changing magnetic flux through a conductor. This changing flux induces eddy currents in the conductor.

4. Present in gaseous currents: While eddy currents are commonly observed in solid conductive materials, they can also occur in gaseous currents. In this case, the conductive medium may be a plasma or ionized gas that exhibits conductive properties.

In summary, eddy currents are induced currents that circulate throughout the volume of a material, similar to swirling eddies in a river. They are caused by a changing magnetic field or the motion of a conductor through a magnetic field. Eddy currents dissipate energy in the form of heat and can be observed in both solid conductive materials and gaseous currents.