# Coulomb > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Coulomb > Markdown URL: https://mediated.wiki/source/Coulomb.md > Source: https://en.wikipedia.org/wiki/Coulomb > Source revision: 1347487296 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) For other uses, see [Coulomb (disambiguation)](/source/Coulomb_(disambiguation)). The **coulomb** (symbol: **C**) is the unit of [electric charge](/source/Electric_charge) in the [International System of Units](/source/International_System_of_Units) (SI).[1][2] It is defined to be equal to the electric charge delivered by a 1 [ampere](/source/Ampere) current in 1 [second](/source/Second), with the [elementary charge](/source/Elementary_charge) *e* as a defining constant in the SI.[2][1] ## Definition The [SI](/source/International_System_of_Units) defines the coulomb as "the quantity of electricity carried in 1 second by a current of 1 ampere" by fixing the value of the [elementary charge](/source/Elementary_charge), .[3] Inverting the relationship, the coulomb can be expressed in terms of the elementary charge: 1 ~ \mathrm{C} = \frac{e}{1.602\,176\,634 \times 10^{-19}} \approx 6.241509\times 10^{18} ~ e . The approximation can be extended to any number of digits. It is not an integer multiple of the elementary charge. The coulomb was [previously defined](/source/Historical_definitions_of_the_SI_base_units) in terms of the [ampere](/source/Ampere) based on the force between two wires, as 1 A × 1 s.[4] The [2019 redefinition of the ampere](/source/2019_revision_of_the_SI#Ampere) and other SI base units fixed the numerical value of the elementary charge when expressed in coulombs and therefore fixed the value of the coulomb when expressed as a multiple of the fundamental charge. ## SI prefixes Main article: [Orders of magnitude (charge)](/source/Orders_of_magnitude_(charge)) Like other SI units, the coulomb can be modified by adding a [prefix](/source/Metric_prefix) that multiplies it by a [power of 10](/source/Power_of_10). ## Conversions - The magnitude of the electrical charge of one [mole](/source/Mole_(unit)) of [elementary charges](/source/Elementary_charge) (approximately , the Avogadro number) is known as a [faraday unit of charge](/source/Faraday_constant) (closely related to the [Faraday constant](/source/Faraday_constant)). One faraday equals In terms of the [Avogadro constant](/source/Avogadro_constant) (*N*A), one coulomb is equal to approximately 1.036×10-5 mol × *N*A elementary charges. - Every [farad](/source/Farad) of [capacitance](/source/Capacitance) can hold one coulomb per [volt](/source/Volt) across the [capacitor](/source/Capacitor). - One [ampere hour](/source/Ampere_hour) equals 3,600 C, hence 1 mA⋅h = 3.6 C. - One [statcoulomb](/source/Statcoulomb) (statC), the obsolete [CGS](/source/CGS) electrostatic unit of charge (esu), is approximately 3.3356×10-10 C or about one-third of a nanocoulomb. ## In everyday terms - The charges in [static electricity](/source/Static_electricity) from rubbing materials together are typically a few microcoulombs.[5] - The amount of charge that travels through a [lightning bolt](/source/Lightning) is typically around 15 C, although for large bolts this can be up to 350 C.[6] - The amount of charge that travels through a typical [alkaline](/source/Alkaline_battery) [AA battery](/source/AA_battery) from being fully charged to discharged is about 5 kC = 5,000 C ≈ 1,400 [mA⋅h](/source/Ampere_hour).[7] - A typical smartphone battery can hold 10,800 C ≈ 3,000 mA⋅h. ## Name and history [8] By 1878, the [British Association for the Advancement of Science](/source/British_Association_for_the_Advancement_of_Science) had defined the volt, ohm, and farad, but not the coulomb.[9] In 1881, the [International Electrical Congress](/source/International_Electrical_Congress), now the [International Electrotechnical Commission](/source/International_Electrotechnical_Commission) (IEC), approved the volt as the unit for electromotive force, the ampere as the unit for electric current, and the coulomb as the unit of electric charge.[10] At that time, the volt was defined as the potential difference [i.e., what is nowadays called the "voltage (difference)"] across a conductor when a current of one ampere dissipates one [watt](/source/Watt) of power. The coulomb (later "absolute coulomb" or "[abcoulomb](/source/Abcoulomb)" for disambiguation) was part of the [EMU](/source/Centimetre%E2%80%93gram%E2%80%93second_system_of_units#Relations_between_ESU_and_EMU_units) system of units. The "international coulomb" based on laboratory specifications for its measurement was introduced by the IEC in 1908. The entire set of "reproducible units" was abandoned in 1948 and the "international coulomb" became the modern coulomb.[11] ## See also - [Abcoulomb](/source/Abcoulomb), a cgs unit of charge - [Ampère's circuital law](/source/Amp%C3%A8re's_circuital_law) - [Coulomb's law](/source/Coulomb's_law) - [Electrostatics](/source/Electrostatics) - [Elementary charge](/source/Elementary_charge) - [Faraday constant](/source/Faraday_constant), the number of coulombs per mole of elementary charges ## Notes and references 1. International Bureau of Weights and Measures (Dec 2022), [*The International System of Units (SI)*](https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf), Vol. 2, no. 1, 9th ed., ISBN 978-92-822-2272-0, [archived](https://web.archive.org/web/20211018184555/https://www.bipm.org/documents/20126/41483022/SI-Brochure-9.pdf/fcf090b2-04e6-88cc-1149-c3e029ad8232) 18 October 2021 at the Wayback Machine 1. BIPM (20 May 2019). ["Mise en pratique for the definition of the ampere in the SI"](https://www.bipm.org/documents/20126/41489676/SI-App2-ampere.pdf/0987a90e-051b-dd7f-827d-3f7b32751a61?version=1.5&t=1637237858322&download=false). *BIPM*. Retrieved 2022-02-18. 1. ["The NIST Reference on Units, Constants, and Uncertainty"](https://physics.nist.gov/cuu/Units/units.html). *NIST*. 12 April 2010. 1. Martin Karl W. Pohl. ["Physics: Principles with Applications"](http://www-zeuthen.desy.de/~pohlmadq/teach/112/ch16.pdf). [DESY](/source/DESY). [Archived](https://web.archive.org/web/20110718230251/http://www-zeuthen.desy.de/~pohlmadq/teach/112/ch16.pdf) 2011-07-18 at the Wayback Machine. 1. Hasbrouck, Richard. [Mitigating Lightning Hazards](https://www.llnl.gov/str/pdfs/05_96.1.pdf) [Archived](https://web.archive.org/web/20131005005230/https://www.llnl.gov/str/pdfs/05_96.1.pdf) 2013-10-05 at the Wayback Machine, Science & Technology Review May 1996. Retrieved on 2009-04-26. 1. [How to do everything with digital photography – David Huss](https://books.google.com/books?id=eftR-e1nVAgC), "The capacity range of an AA battery is typically from 1100–2200 mAh." 1. ["SI Brochure, Appendix 1"](http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf). BIPM. p. 144. [Archived](https://web.archive.org/web/20060618214631/http://www1.bipm.org/utils/common/pdf/si_brochure_8_en.pdf) 2006-06-18 at the Wayback Machine. 1. W. Thomson, et al. (1873) ["First report of the Committee for the Selection and Nomenclature of Dynamical and Electrical Units,"](https://www.biodiversitylibrary.org/page/29853513#page/324/mode/1up) *Report of the 43rd Meeting of the British Association for the Advancement of Science* (Bradford, September 1873), pp. 222–225. From p. 223: "The 'ohm', as represented by the original standard coil, is approximately 109 C.G.S. units of resistance; the 'volt' is approximately 108 C.G.S. units of electromotive force; and the 'farad' is approximately 1/109 of the C.G.S. unit of capacity." 1. (Anon.) (September 24, 1881) ["The Electrical Congress"](https://babel.hathitrust.org/cgi/pt?id=nyp.33433090837489;view=1up;seq=309), *The Electrician*, **7**. 1. Donald Fenna, *A Dictionary of Weights, Measures, and Units*, OUP (2002), 51f. --- Adapted from the Wikipedia article [Coulomb](https://en.wikipedia.org/wiki/Coulomb) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Coulomb?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.