The tesla (symbol: T) is the unit of magnetic flux density (B) (also called magnetic B-field) in the International System of Units (SI). One tesla is equal to one weber per square metre. The unit was announced during the General Conference on Weights and Measures in 1960 and is named in honour of Serbian-American electrical and mechanical engineer Nikola Tesla, upon the proposal of the Slovenian electrical engineer France Avčin. As with every SI unit named after a person, its symbol is upper case (T) but the name of the unit is written in sentence case (tesla).
Definition
A particle, carrying a charge of one coulomb (C), and moving perpendicularly through a magnetic field of one tesla, at a speed of one metre per second (m/s), experiences a force with magnitude one newton (N), according to the Lorentz force law. That is,
T = N ⋅ s C ⋅ m . {\displaystyle \mathrm {T={\dfrac {N{\cdot }s}{C{\cdot }m}}} .}
Expressed in SI base units, 1 tesla is:
T = k g A ⋅ s 2 , {\displaystyle \mathrm {T={\dfrac {kg}{A{\cdot }s^{2}}}} ,}
where A is ampere, kg is kilogram, and s is second.
In terms of other SI derived units As an SI derived unit, the tesla can also be expressed in terms of other units. For example, a magnetic flux of 1 weber (Wb) through a surface of one square meter is equal to a magnetic flux density of 1 tesla. That is,
T = W b m 2 . {\displaystyle \mathrm {T={\dfrac {Wb}{m^{2}}}} .}
Additional equivalences result from the derivation of coulombs from amperes (A), C = A ⋅ s {\displaystyle \mathrm {C=A{\cdot }s} } :
T = N A ⋅ m , {\displaystyle \mathrm {T={\dfrac {N}{A{\cdot }m}}} ,}
the relationship between newtons and joules (J), J = N ⋅ m {\displaystyle \mathrm {J=N{\cdot }m} } :
T = J A ⋅ m 2 , {\displaystyle \mathrm {T={\dfrac {J}{A{\cdot }m^{2}}}} ,}
and the derivation of the weber from volts (V), W b = V ⋅ s {\displaystyle \mathrm {Wb=V{\cdot }s} } :
T = V ⋅ s m 2 . {\displaystyle \mathrm {T={\dfrac {V{\cdot }{s}}{m^{2}}}} .}
Conversion to non-SI units The CGS system has a unit similar to the tesla called the gauss. One tesla corresponds to 104 G, but there are subtle differences in the meaning of the units and the gauss is not acceptable for use with SI units according to NIST guidelines. The unit γ (gamma), formerly used in geophysics and defined as 10-5 G, corresponds to 10-9 T. The modern convention is to use the nanotesla (nT) instead of γ. The 2019 revision of the SI changed the definition of the ampere and that changed the definition of the tesla by 106.67 parts in 109. The revision also changed the definition of the permeability constant, μ 0 {\displaystyle \mu _{0}} , altering the meaning of conversions between SI units like the tesla and CGS units like the gauss, and making them a little uncertain. Use of these conversions has been discouraged in scholarly journals.
Examples
The following examples are listed in the ascending order of the magnetic-field strength.
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