Magnetic flux area S is where "B" is the magnitude of the magnetic field (the magnetic flux density) having the unit of Wb/m (tesla), "S" is the area of the surface, and "θ" is the angle between the magnetic field lines and the normal (perpendicular) to S. For a varying magnetic field, we first consider the magnetic flux through an infinitesimal area element dS, where we may consider the field to be constant: A generic surface, S, can then be broken into infinitesimal elements and the total magnetic flux through the surface is then the surface integral From the definition of the
Magnetic flux boundary ∂Σ and, secondly, as the change of magnetic flux through the open surface Σ. This equation is the principle behind an electrical generator. By way of contrast, Gauss's law for electric fields, another of Maxwell's equations, is where Note that the flux of E through a closed surface is "not" always zero; this indicates the presence of "electric monopoles", that is, free positive or negative charges. Magnetic flux In physics, specifically electromagnetism, the magnetic flux (often denoted or ) through a surface is the surface integral of the normal component of the magnetic field B passing through that surface.