Weber (unit)


In physics, the weber is the SI derived unit of magnetic flux. A flux density of one Wb/m2 is one tesla.
The weber is named after the German physicist Wilhelm Eduard Weber.

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.
Officially:
The weber is commonly expressed in a multitude of other units:
where
Wb = weber,
Ω = ohm,
C = coulomb,
V = volt,
T = tesla,
J = joule,
m = metre,
s = second,
A = ampere,
H = henry,
Mx = maxwell.

History

In 1861, the British Association for the Advancement of Science established a committee under William Thomson to study electrical units. In a February 1902 manuscript, with handwritten notes of Oliver Heaviside, Giovanni Giorgi proposed a set of rational units of electromagnetism including the weber, noting that "the product of the volt into the second has been called the weber by the B. A."
The International Electrotechnical Commission began work on terminology in 1909 and established Technical Committee 1 in 1911, its oldest established committee, "to sanction the terms and definitions used in the different electrotechnical fields and to determine the equivalence of the terms used in the different languages."
In 1930, TC1 decided that the magnetic field strength is of a different nature from the magnetic flux density, and took up the question of naming the units for these fields and related quantities, among them the integral of magnetic flux density.
In 1935, TC 1 recommended names for several electrical units, including the weber for the practical unit of magnetic flux.
Also in 1935, TC1 passed responsibility for "electric and magnetic magnitudes and units" to the new TC24. This "led eventually to the universal adoption of the Giorgi system, which unified electromagnetic units with the MKS dimensional system of units, the whole now known simply as the SI system."
In 1938, TC24 "recommended as a connecting link the permeability of free space with the value of μ0 = 4π H/m. This group also recognized that any one of the practical units already in use, could equally serve as the fourth fundamental unit. "After consultation, the ampere was adopted as the fourth unit of the Giorgi system in Paris in 1950."