Closed magnetic circuit (magnetic field)


An electromagnet is a type of magnet in which the magnetic field is produced by electric current. The magnetic field disappears when the current is turned off. Electromagnets usually consist of a large number of closely spaced turns of wire that create the magnetic field. The wire turns are often wound around a magnetic core made from a ferromagnetic or ferrimagnetic material such as iron; the magnetic core concentrates the magnetic flux and makes a more powerful magnet. For a closed magnetic circuit (no air gap), such as would be found in an electromagnet lifting a piece of iron bridged across its poles the magnetic field can be calculated by the average length of the magnetic circuit and the electric current.

Related formulas


BThe magnetic field (T)
NThe number of turns (dimensionless)
IThe electic current (A)
μ the magnetic permeability of the core material (H/m)
LThe average length of the magnetic circuit (m)