Quantities and Units of Magnetism

Magnetic flux is a measure of the quantity of magnetism, being the total number of magnetic lines of force passing through a specified area in a magnetic field. It represents the strength of the magnetic field over a given area. The SI unit is weber (symbol Wb).

Inductance or self inductance is the property of a electrical circuit to oppose a change in current. The moving magnetic field produced by a change in current causes an induced voltage to oppose the original change. The ratio of the magnetic flux produced to the current is called the inductance. SI unit is henry (symbol H), or Weber per ampere.

Magnetic field strength is the intensity of a magnetic field at a given location, a vector quantity indicating the ability of a magnetic field to exert a force on moving electric charges. It is equal to the magnetic flux density divided by the magnetic permeability of the space where the field exists. SI derived unit is amperes per meter (symbol A/m).

Magnetic flux density , or magnetic induction is the amount of magnetic flux through a unit area taken perpendicular to the direction of the magnetic flux, a vector quantity measuring the strength and direction of the magnetic field around a magnet or an electric current. It is equal to magnetic field strength times the magnetic permeability in the region in which the field exists. The SI unit is tesla (symbol T), or N/(A·m) expressed in SI base unit.

Magnetomotive force, or magnetic potential difference, is any physical cause that produces magnetic flux. It is analogous to electromotive force. The SI unit is ampere (symbol A). The obsolete unit ampere turn.