Magnetic Flux refers to a measure of the strength of a magnetic field over a given area. The SI unit of magnetic flux is the weber (Wb) (in derived units: volt-seconds). The CGS unit is the maxwell. The magnetic flux through a given surface is proportional to the number of magnetic B field lines that pass through the surface. The apparatus used to measure magnetic flux is called a flux meter; it consists of coils and electronics which evaluate the voltage change in the coil to measure the magnetic flux. It is measured in maxwells or webers: symbol, Φ.