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The magnetic field (marked B, indicated by red field lines) around wire carrying an electric current (marked I) Compass and wire apparatus showing Ørsted's experiment (video [1]) In electromagnetism , Ørsted's law , also spelled Oersted's law , is the physical law stating that an electric current induces a magnetic field .
When the electric current in a loop of wire changes, the changing current creates a changing magnetic field. A second wire in reach of this magnetic field will experience this change in magnetic field as a change in its coupled magnetic flux, . Therefore, an electromotive force is set up in the second loop called the induced emf or transformer emf.
In electromagnetism, an eddy current (also called Foucault's current) is a loop of electric current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction or by the relative motion of a conductor in a magnetic field. Eddy currents flow in closed loops within conductors, in planes ...
An electric current flowing in a wire creates a magnetic field around the wire, due to Ampere's law (see drawing of wire with magnetic field). To concentrate the magnetic field in an electromagnet, the wire is wound into a coil with many turns of wire lying side by side. [2] The magnetic field of all the turns of wire passes through the center ...
[15] [16] Maxwell's extension to the law states that a time-varying electric field can also generate a magnetic field. [12] Similarly, Faraday's law of induction states that a magnetic field can produce an electric current. For example, a magnet pushed in and out of a coil of wires can produce an electric current in the coils which is ...
Magnetic poles (or states of polarization at individual points) attract or repel one another in a manner similar to positive and negative charges and always exist as pairs: every north pole is yoked to a south pole. [8] An electric current inside a wire creates a corresponding circumferential magnetic field outside the wire.
Sparks — Electrical breakdown of a medium that produces an ongoing plasma discharge, similar to the instant spark, resulting from a current flowing through normally nonconductive media such as air. Telluric currents — Extremely low frequency electric current that occurs naturally over large underground areas at or near the surface of the Earth.
In many useful cases, a distribution of electric charge can be mathematically replaced by an equivalent distribution of magnetic current. This artifice can be used to simplify some electromagnetic field problems. [b] [c] It is possible to use both electric current densities and magnetic current densities in the same analysis. [4]: 138