Ampere
The ampere (symbol: A) is the SI unit of electric current, and one of the seven base units in the International System of Units (SI). It is named after the French physicist André-Marie Ampère (1775–1836).
A similar unit, used for pratical measurements of current, is the conventional ampere (A90).[Note 1] The 2006 CODATA recommended value for A90 is:[1]
- A90 = V90/Ω90 = (KJ–90RK–90/KJRK) V = [1 − 0.3(2.5) × 10−8] A
The international ampere (symbol: Aint) is now obsolete.
Definition
The current definition of the ampere was approved by the 9th General Conference on Wieghts and Measures in 1948:[2][3]
The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 × 10−7 newton per metre of length.
This definition, which is based on the Biot–Savart law, has the effect of fixing the value of the magnetic constant μ0 in SI units, so that {{{1}}}.
Notes and references
Notes
References
- ↑ Mohr, Peter J.; Taylor, Barry N.; Newell, David B. CODATA Recommended Values of the Fundamental Physical Constants: 2006. Rev. Mod. Phys. 2008, 80 (2), 633–730. doi:10.1103/RevModPhys.80.633, <http://physics.nist.gov/cuu/Constants/codata.pdf>.
- ↑ 9th CGPM (1948), Resolution 2.
- ↑ 3.0 3.1 The International System of Units (SI), 8th ed.; International Bureau of Weights and Measures: Sèvres, France, 2006; p 113. ISBN 92-822-2213-6, <http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf>.
- ↑ 9th CGPM (1948), Resolution 7.
External links
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See also the corresponding article on Wikipedia. |
- ampere at Sizes.com
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