Flux surface surrounding a charge "q" is "q"/ε. In free space the electric displacement is given by the constitutive relation D = ε E, so for any bounding surface the D-field flux equals the charge "Q" within it. Here the expression "flux of" indicates a mathematical operation and, as can be seen, the result is not necessarily a "flow", since nothing actually flows along electric field lines. The magnetic flux density (magnetic field) having the unit Wb/m (Tesla) is denoted by B, and magnetic flux is defined analogously: with the same notation above. The quantity arises in Faraday's law of induction,
International System of Electrical and Magnetic Units International System of Electrical and Magnetic Units The International System of Electrical and Magnetic Units is an obsolete system of units used for measuring electrical and magnetic quantities. It was proposed as a system of practical international units by unanimous recommendation at the International Electrical Congress (Chicago, 1893), discussed at other Congresses, and finally adopted at the International Conference on Electric Units and Standards in London in 1908. It was rendered obsolete by the inclusion of electromagnetic units in the International System of Units (SI) at the 9th General Conference on Weights and Measures in 1948. The link between electromagnetic