Magneettiflussin

Magneettiflussin, or magnetic flux, is a measure of the amount of magnetic field passing through a given surface. It is denoted by the symbol ΦB and is defined as the surface integral of the magnetic field B over a surface S: ΦB = ∫S B · dA. When the field is uniform and the surface is flat with area A and angle θ between B and the surface normal, ΦB = B A cos θ. The flux is measured in webers (Wb), where 1 Wb = 1 V·s = 1 T·m².

The flux depends on the local magnetic field and the orientation and size of the surface. The magnetic flux through a closed surface is related to Gauss’s law for magnetism, which states that the net flux through any closed surface is zero in the absence of magnetic monopoles; this reflects that magnetic field lines form closed loops.

Magnetic flux is closely related to magnetic flux density B, the local field. When B and the surface are fixed, changing the surface area or orientation changes the flux. Faraday’s law of induction connects the changing magnetic flux to electromotive force: ε = − dΦB/dt. This principle underpins transformers, inductors, and many electric machines.

In coils with N turns, the flux linkage is Ψ = NΦB, and inductance L is defined by Ψ = L I. Materials influence flux through the relation B = μH, where μ = μ0 μr combines the permeability of free space with the material’s relative permeability. Magnetic circuits and saturation effects in ferromagnetic materials also affect flux behavior.