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Definition

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 magnetic flux) — The weber is the magnetic flux that, linking a circuit of one turn, would produce in it an electromotive force of 1 volt if it were reduced to zero at a uniform rate in 1 second.

That is:

One weber is also the total magnetic flux across a surface of one square meter perpendicular to a magnetic flux density of one tesla; that is,

Expressed only in SI base units, 1 weber is:

The weber is used in the definition of the henry as 1 weber per ampere, and consequently can be expressed as the product of those units:

The weber is commonly expressed in a multitude of other units:

where Ω is ohm, C is coulomb, J is joule, and N is newton.

The weber is named after Wilhelm Eduard Weber. As with every SI unit named for a person, its symbol starts with an upper case letter (Wb), but when written in full, it follows the rules for capitalisation of a common noun; i.e., weber becomes capitalised at the beginning of a sentence and in titles but is otherwise in lower case.