In
physics
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...
, the weber ( ; symbol: Wb) is the unit of
magnetic flux in the
International System of Units (SI), whose units are volt-second. A
magnetic flux density
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
of one Wb/m
2 (one weber per square
metre
The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its prefi ...
) is one
tesla.
The weber is named after the
German
German(s) may refer to:
* Germany (of or related to)
** Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ge ...
physicist
Wilhelm Eduard Weber
Wilhelm Eduard Weber (; ; 24 October 1804 – 23 June 1891) was a German physicist and, together with Carl Friedrich Gauss, inventor of the first electromagnetic telegraph.
Biography of Wilhelm
Early years
Weber was born in Schlossstrasse i ...
(1804–1891).
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
The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827).
Defin ...
(produce an electric
potential difference
Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...
of one volt across two open-circuited terminals).
Officially:
That is:
One weber is also the total magnetix 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 tesla is:
The weber is used in the definition of the
henry
Henry may refer to:
People
*Henry (given name)
* Henry (surname)
* Henry Lau, Canadian singer and musician who performs under the mononym Henry
Royalty
* Portuguese royalty
** King-Cardinal Henry, King of Portugal
** Henry, Count of Portugal, ...
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
History
In 1861, the
British Association for the Advancement of Science (known as "The BA") established a committee under William Thomson (later
Lord Kelvin
William Thomson, 1st Baron Kelvin, (26 June 182417 December 1907) was a British mathematician, mathematical physicist and engineer born in Belfast. Professor of Natural Philosophy at the University of Glasgow for 53 years, he did important ...
) to study electrical units.
[
] In a February 1902 manuscript, with handwritten notes of
Oliver Heaviside
Oliver Heaviside FRS (; 18 May 1850 – 3 February 1925) was an English self-taught mathematician and physicist who invented a new technique for solving differential equations (equivalent to the Laplace transform), independently developed ...
,
Giovanni Giorgi
Giovanni Giorgi (November 27, 1871 – August 19, 1950) was an Italian physicist and electrical engineer who proposed the ''Giorgi system'' of measurement, the precursor to the International System of Units (SI).
Early Life
Giovanni Giorgi was ...
proposed a set of rational units of
electromagnetism
In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of ...
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 In physics, field strength means the ''magnitude'' of a vector-valued field (e.g., in volts per meter, V/m, for an electric field ''E'').
For example, an electromagnetic field results in both electric field strength and magnetic field strength ...
(H) is of a different nature from the
magnetic flux density
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
(B),
[ 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).][
: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]
/ref>
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 system of units, MKS dimensional system of units, the whole now known simply as the SI system (Système International d'unités)."[
]
In 1938, TC24 "recommended as a connecting link rom mechanical to electrical unitsthe permeability of free space with the value of ''μ''0 = 4π H/m. This group also recognized that any one of the practical units already in use (ohm
Ohm (symbol Ω) is a unit of electrical resistance named after Georg Ohm.
Ohm or OHM may also refer to:
People
* Georg Ohm (1789–1854), German physicist and namesake of the term ''ohm''
* Germán Ohm (born 1936), Mexican boxer
* Jörg Ohm (b ...
, ampere, volt
The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827).
Defin ...
, henry
Henry may refer to:
People
*Henry (given name)
* Henry (surname)
* Henry Lau, Canadian singer and musician who performs under the mononym Henry
Royalty
* Portuguese royalty
** King-Cardinal Henry, King of Portugal
** Henry, Count of Portugal, ...
, farad, coulomb, and weber), 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."
Multiples
Like other SI units, the weber can modified by adding a prefix that multiplies it by a power of 10
A power of 10 is any of the integer powers of the number ten; in other words, ten multiplied by itself a certain number of times (when the power is a positive integer). By definition, the number one is a power (the zeroth power) of ten. The f ...
.
Conversions
* One maxwell (Mx), the CGS unit of magnetic flux, equals 10−8 Wb
Notes and references
{{DEFAULTSORT:Weber (Unit)
SI derived units
Units of magnetic flux