# Weber (unit)

In physics, the weber /ˈveɪbər/[1] (symbol: Wb) is the SI derived unit of magnetic flux. A flux density of one Wb/m2 (one weber per square metre) is one tesla.

The weber is named after the German physicist Wilhelm Eduard Weber (1804–1891).

Weber
Unit systemSI derived unit
SymbolWb
Named afterWilhelm Eduard Weber
In SI base units:kgm2s−2A−1

## Definition

Submultiples Multiples Value SI symbol Name Value 10−1 Wb dWb deciweber 101 Wb daWb decaweber 10−2 Wb cWb centiweber 102 Wb hWb hectoweber 10−3 Wb mWb milliweber 103 Wb kWb kiloweber 10−6 Wb µWb microweber 106 Wb MWb megaweber 10−9 Wb nWb nanoweber 109 Wb GWb gigaweber 10−12 Wb pWb picoweber 1012 Wb TWb teraweber 10−15 Wb fWb femtoweber 1015 Wb PWb petaweber 10−18 Wb aWb attoweber 1018 Wb EWb exaweber 10−21 Wb zWb zeptoweber 1021 Wb ZWb zettaweber 10−24 Wb yWb yoctoweber 1024 Wb YWb yottaweber Common multiples are in bold face.

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.[2]

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

${\displaystyle \mathrm {Wb} ={\dfrac {\mathrm {kg} {\cdot }\mathrm {m} ^{2}}{\mathrm {s} ^{2}{\cdot }\mathrm {A} }}=\mathrm {V} {\cdot }\mathrm {s} =\mathrm {H} {\cdot }\mathrm {A} =\mathrm {T} {\cdot }\mathrm {m} ^{2}={\dfrac {\mathrm {J} }{\mathrm {A} }}=10^{8}\mathrm {Mx} }$

where Wb = weber,
V = volt,
T = tesla,
J = joule,
m = metre,
s = second,
A = ampere,
H = henry,
Mx = maxwell.

This SI unit is named after Wilhelm Eduard Weber. As with every International System of Units (SI) unit named for a person, the first letter of its symbol is upper case (Wb). However, when an SI unit is spelled out in English, it is treated as a common noun and should always begin with a lower case letter (weber)—except in a situation where any word in that position would be capitalized, such as at the beginning of a sentence or in material using title case.

## History

In 1861, the British Association for the Advancement of Science (known as "The BA"[3]) established a committee under William Thomson (later Lord Kelvin) to study electrical units.[4] 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."[5]

The International Electrotechnical Commission began work on terminology in 1909 and established Technical Committee 1 in 1911, its oldest established committee,[6] "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."[7]

It was not until 1927 that TC1 dealt with the study of various outstanding problems concerning electrical and magnetic quantities and units. Discussions of a theoretical nature were opened at which eminent electrical engineers and physicists considered whether magnetic field strength and magnetic flux density were in fact quantities of the same nature. As disagreement continued, the IEC decided on an effort to remedy the situation. It instructed a task force to study the question in readiness for the next meeting.[8]

In 1930, TC1 decided that the magnetic field strength (H) is of a different nature from the magnetic flux density (B),[8] 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 (and the maxwell for the CGS unit).[8][9]

It was decided to extend the existing series of practical units into a complete comprehensive system of physical units, the recommendation being adopted in 1935 "that the system with four fundamental units proposed by Professor Giorgi be adopted subject to the fourth fundamental unit being eventually selected". This system was given the designation of "Giorgi system".[10]

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 (Système International d’unités)."[11]

In 1938, TC24 "recommended as a connecting link [from mechanical to electrical units] the permeability of free space with the value of µ0 = 4π×107 H/m. This group also recognized that any one of the practical units already in use (ohm, ampere, volt, henry, farad, coulomb, and weber), could equally serve as the fourth fundamental unit.[8] "After consultation, the ampere was adopted as the fourth unit of the Giorgi system in Paris in 1950."[10]

## Notes and references

1. ^ In America also /ˈwɛbər/.
"weber (main entry is American English, Collins World English (further down) is British)". Dictionary.com.
2. ^ "CIPM, 1946: Resolution 2 / Definitions of Electrical Units". International Committee for Weights and Measures (CIPM) Resolutions. International Bureau of Weights and Measures (BIPM). 1946. Retrieved 2008-04-29.
3. ^
4. ^ Frary, Mark. "In the beginning...The world of electricity: 1820-1904". International Electrotechnical Commission. Retrieved 2018-04-19.
5. ^ Giorgi, Giovanni (February 1902). "Rational Units of Electromagnetism" (Manuscript with handwritten notes by Oliver Heaviside). p. 9. Retrieved 2014-02-21.
6. ^ "Strategic Policy Statement, IEC Technical Committee on Terminology" (PDF). International Electrotechnical Commission. Archived from the original (PDF) on 2006-09-04. Retrieved 2008-04-29.
7. ^ "IEC Technical Committee 1". International Electrotechnical Commission. Retrieved 2018-04-19.
8. ^ a b c d "The role of the IEC / Work on quantities and units". History of the SI. International Electrotechnical Commission. Archived from the original on 25 Sep 2013. Retrieved 2018-04-19.
9. ^ "Summary: Electrical Units". IEC History. International Electrotechnical Commission. Retrieved 2018-04-19.
This page incorrectly states that the units were established in 1930, since that year, TC 1 decided "that the question of names to be allocated to magnetic units should not be considered until general agreement had been reached on their definitions" [1]
10. ^ a b Ruppert, Louis (1956). Brief History of the International Electrotechnical Commission (PDF). International Electrotechnical Commission. p. 5. Retrieved 2018-04-19.
11. ^ Raeburn, Anthony. "Overview: IEC technical committee creation: the first half-century (1906-1949)". International Electrotechnical Commission. Retrieved 2018-04-19.
Index of physics articles (W)

The index of physics articles is split into multiple pages due to its size.

To navigate by individual letter use the table of contents below.

List of scientists whose names are used as SI units

List of scientists whose names are used as SI units is the list of those scientists whose names are assigned as the names of the international units by the International Committee for Weights and Measures. The International System of Units (abbreviated SI from French: Système international d'unités) is the most widely used system of units of measurement. There are seven base units and 22 derived units (excluding compound units). These units are used both in science and in commerce. Two of the base units and 17 of the derived units are named after scientists. By this convention, their names are immortalised. Below is the list of the scientists whose names are used as SI units. As a rule, the units are written in lowercase letters, but symbols of units derived from the name of a person begin with a capital letter.

Maxwell (unit)

The maxwell (symbol: Mx) is the CGS (centimetre-gram-second) unit of magnetic flux (Φ).

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.