weber | |
---|---|

Unit system | SI |

Unit of | magnetic flux |

Symbol | Wb |

Named after | Wilhelm Eduard Weber |

Conversions | |

1 Wb in ... | ... is equal to ... |

SI base units | 1 kg⋅m ^{2}⋅s ^{−2}⋅A ^{−1} |

Gaussian units | 1×10^{8} Mx |

In physics, the **weber** ( /ˈveɪb-,ˈwɛb.ər/ *VAY-, WEH-bər*;^{ [1] }^{ [2] } symbol: **Wb**) is the unit of magnetic flux in the International System of Units (SI). The unit is derived (through Faraday's law of induction) from the relationship 1 Wb = 1 V⋅s (volt-second). A magnetic flux density of 1 Wb/m^{2} (one weber per square metre) is one tesla.

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

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.

^{ [3] }

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^{[ citation needed ]}:

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.

In 1861, the British Association for the Advancement of Science (known as "The BA"^{ [4] }) established a committee under William Thomson (later Lord Kelvin) to study electrical units.^{ [5] } 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."^{ [6] }

The International Electrotechnical Commission began work on terminology in 1909 and established Technical Committee 1 in 1911, its oldest established committee,^{ [7] } "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."^{ [8] }

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.

^{ [9] }

In 1930, TC1 decided that the magnetic field strength (**H**) is of a different nature from the magnetic flux density (**B**),^{ [9] } and took up the question of naming the units for these fields and related quantities, among them the integral of magnetic flux density.^{[ citation needed ]}

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).^{ [9] }^{ [10] }

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".

^{ [11] }

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)."^{ [12] }

In 1938, TC24 "recommended as a connecting link [from mechanical to electrical units] the permeability of free space with the value of *μ*_{0} = 4π×10^{−7} 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.^{ [9] } "After consultation, the ampere was adopted as the fourth unit of the Giorgi system in Paris in 1950."^{ [11] }

Like other SI units, the weber can modified by adding a prefix that multiplies it by a power of 10.

Submultiples | Multiples | ||||
---|---|---|---|---|---|

Value | SI symbol | Name | Value | SI symbol | Name |

10^{−1} Wb | dWb | deciweber | 10^{1} Wb | daWb | decaweber |

10^{−2} Wb | cWb | centiweber | 10^{2} Wb | hWb | hectoweber |

10^{−3} Wb | mWb | milliweber | 10^{3} Wb | kWb | kiloweber |

10^{−6} Wb | μWb | microweber | 10^{6} Wb | MWb | megaweber |

10^{−9} Wb | nWb | nanoweber | 10^{9} Wb | GWb | gigaweber |

10^{−12} Wb | pWb | picoweber | 10^{12} Wb | TWb | teraweber |

10^{−15} Wb | fWb | femtoweber | 10^{15} Wb | PWb | petaweber |

10^{−18} Wb | aWb | attoweber | 10^{18} Wb | EWb | exaweber |

10^{−21} Wb | zWb | zeptoweber | 10^{21} Wb | ZWb | zettaweber |

10^{−24} Wb | yWb | yoctoweber | 10^{24} Wb | YWb | yottaweber |

10^{−27} Wb | rWb | rontoweber | 10^{27} Wb | RWb | ronnaweber |

10^{−30} Wb | qWb | quectoweber | 10^{30} Wb | QWb | quettaweber |

Common multiples are in bold face. |

- ↑ Wells, John (3 April 2008).
*Longman Pronunciation Dictionary*(3rd ed.). Pearson Longman. ISBN 978-1-4058-8118-0. - ↑ "weber (main entry is American English, Collins World English (further down) is British)".
*Dictionary.com*. - ↑ "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. - ↑ "The BA (British Association for the Advancement of Science)".
- ↑ Frary, Mark. "In the beginning...The world of electricity: 1820-1904". International Electrotechnical Commission. Retrieved 2018-04-19.
- ↑ Giorgi, Giovanni (February 1902). "Rational Units of Electromagnetism" (Manuscript with handwritten notes by Oliver Heaviside). p. 9. Retrieved 2014-02-21.
- ↑ "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.
- ↑ "IEC Technical Committee 1". International Electrotechnical Commission. Retrieved 2018-04-19.
- 1 2 3 4 "The role of the IEC / Work on quantities and units".
*History of the SI*. International Electrotechnical Commission. Archived from the original on 11 June 2007. Retrieved 2018-04-19. - ↑ "Summary: Electrical Units".
*IEC History*. International Electrotechnical Commission. Retrieved 2018-04-19. - 1 2 Ruppert, Louis (1956).
*Brief History of the International Electrotechnical Commission*(PDF). International Electrotechnical Commission. p. 5. Retrieved 2018-04-19. - ↑ Raeburn, Anthony. "Overview: IEC technical committee creation: the first half-century (1906-1949)". International Electrotechnical Commission. Retrieved 2018-04-19.

The **centimetre–gram–second system of units** is a variant of the metric system based on the centimetre as the unit of length, the gram as the unit of mass, and the second as the unit of time. All CGS mechanical units are unambiguously derived from these three base units, but there are several different ways in which the CGS system was extended to cover electromagnetism.

The **gauss**, is a unit of measurement of magnetic induction, also known as magnetic flux density. The unit is part of the Gaussian system of units, which inherited it from the older centimetre–gram–second electromagnetic units (CGS-EMU) system. It was named after the German mathematician and physicist Carl Friedrich Gauss in 1936. One gauss is defined as one maxwell per square centimetre.

The **volt** is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI).

The **coulomb** (symbol: **C**) is the unit of electric charge in the International System of Units (SI). In the present version of the SI it is equal to the electric charge delivered by a 1 ampere constant current in 1 second and to 5×10^{27}/801088317 elementary charges, `e`, (about 6.241509×10^{18}`e`).

The **oersted** is the coherent derived unit of the auxiliary magnetic field **H** in the centimetre–gram–second system of units (CGS). It is equivalent to 1 dyne per maxwell.

In physics, specifically electromagnetism, the **magnetic flux** through a surface is the surface integral of the normal component of the magnetic field **B** over that surface. It is usually denoted Φ or Φ_{B}. The SI unit of magnetic flux is the weber, and the CGS unit is the maxwell. Magnetic flux is usually measured with a fluxmeter, which contains measuring coils, and it calculates the magnetic flux from the change of voltage on the coils.

The **henry** is the unit of electrical inductance in the International System of Units (SI). If a current of 1 ampere flowing through a coil produces flux linkage of 1 weber turn, that coil has a self inductance of 1 henry. The unit is named after Joseph Henry (1797–1878), the American scientist who discovered electromagnetic induction independently of and at about the same time as Michael Faraday (1791–1867) in England.

The **maxwell** is the CGS (centimetre–gram–second) unit of magnetic flux.

The **tesla** is the unit of magnetic flux density in the International System of Units (SI).

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A **magnetic circuit** is made up of one or more closed loop paths containing a magnetic flux. The flux is usually generated by permanent magnets or electromagnets and confined to the path by magnetic cores consisting of ferromagnetic materials like iron, although there may be air gaps or other materials in the path. Magnetic circuits are employed to efficiently channel magnetic fields in many devices such as electric motors, generators, transformers, relays, lifting electromagnets, SQUIDs, galvanometers, and magnetic recording heads.

**Permeance**, in general, is the degree to which a material admits a flow of matter or energy. Permeance is usually represented by a curly capital P: P.

**Magnetic reluctance**, or **magnetic resistance**, is a concept used in the analysis of magnetic circuits. It is defined as the ratio of magnetomotive force (mmf) to magnetic flux. It represents the opposition to magnetic flux, and depends on the geometry and composition of an object.

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In electromagnetism, **current density** is the amount of charge per unit time that flows through a unit area of a chosen cross section. The **current density vector** is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the positive charges at this point. In SI base units, the electric current density is measured in amperes per square metre.

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The **gyrator–capacitor model** - sometimes also the capacitor-permeance model - is a lumped-element model for magnetic circuits, that can be used in place of the more common resistance–reluctance model. The model makes permeance elements analogous to electrical capacitance rather than electrical resistance. Windings are represented as gyrators, interfacing between the electrical circuit and the magnetic model.

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, 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.

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