fluks

Fluks is a term used in Dutch and other languages to denote flux, the rate at which a quantity passes through a surface or region. In physics, engineering and related sciences, fluks describes the flow of a physical quantity per unit area or per unit time and appears in a variety of contexts.

Electric and magnetic flux are common specializations. Electric flux through a surface S is defined as Φ_E = ∮_S E · dA, where E is the electric field and dA is an outward-oriented area element. Its SI unit is volt-meter (V·m). Gauss’s law links Φ_E to the enclosed charge. Magnetic flux through a surface is Φ_B = ∮_S B · dA, with B the magnetic field and the unit the weber (Wb). Faraday’s law relates a changing Φ_B to the induced electric field.

In a broader mathematical sense, flux is the surface integral of a vector field across a surface: ∬_S F · n dS, where F is a vector field and n is the surface normal. The flux through a closed surface connects to volume properties via the divergence theorem: ∬_S F · n dS = ∭_V div F dV.

Other types of flux occur in engineering and physical chemistry. Mass flux measures the transport of mass per unit area per unit time (e.g., J_m = ρ v for a flow). Heat flux quantifies energy transfer as heat per unit area per unit time (q'' = -k ∇T in conductive media). The concept also appears in fluid dynamics as volumetric flux and in radiative transfer as photon flux.

Etymology derives from Latin fluxus, meaning flow or discharge. In Dutch and scientific writing, fluks is used interchangeably with flux to describe these transfer rates and surface-intersection quantities.