Weber (unit) Weber (unit) In physics, the weber (symbol: Wb) is the SI unit of magnetic flux. A "flux density" of one Wb/m (one weber per square metre) is one tesla. The weber is named after the German physicist Wilhelm Eduard Weber (1804–1891). The weber may be defined in terms of Faraday's law, which relates a changing magnetic flux through a loop to the electric field around the loop. A change in flux of one weber per second will induce an electromotive force of one volt (produce an electric potential difference of one volt across two open-circuited terminals). Officially, Weber (unit of
Radiant energy density Radiant energy density In radiometry, radiant energy density is the radiant energy per unit volume. The SI unit of radiant energy density is the joule per cubic metre (J/m). Radiant energy density, denoted "w" ("e" for "energetic", to avoid confusion with photometric quantities), is defined as where Because radiation always "transmits" the energy, it is useful to wonder what the speed of the transmission is. If all the radiation at given location propagates in the same direction, then the radiant flux through a unit area perpendicular to the propagation direction is given by the irradiance: where "c" is the radiation