The coulomb is named after Charles-Augustin de Coulomb. As with every SI unit named for a person, its symbol starts with an upper case letter (C), but when written in full it follows the rules for capitalisation of a common noun; i.e., "coulomb" becomes capitalised at the beginning of a sentence and in titles, but is otherwise in lower case.
By 1878, the British Association for the Advancement of Science had defined the volt, ohm, and farad, but not the coulomb. In 1881, the International Electrical Congress, now the 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.
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 of power.
The coulomb (later "absolute coulomb" or "abcoulomb" for disambiguation) was part of the EMU 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.
One coulomb is the charge of approximately 6241509074460762607.776 elementary charges, where the number is the reciprocal of 1.602176634×10−19 C. This is also 160.2176634 zC of charge.
The exact value of 1 coulomb is
^6.241509074...×1018 is the reciprocal of the 2018 CODATA recommended value of the elementary charge, 1.602176634×10−19 C.
"SI Brochure (2019)" (PDF). SI Brochure. BIPM. p. 127. Retrieved May 23, 2019.
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^"SI Brochure, Appendix 1" (PDF). BIPM. p. 144. Archived (PDF) from the original on 2006-06-18.
^W. Thomson, et al. (1873) "First report of the Committee for the Selection and Nomenclature of Dynamical and Electrical Units," 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."
^(Anon.) (September 24, 1881) "The Electrical Congress," The Electrician, 7.
^Donald Fenna, A Dictionary of Weights, Measures, and Units, OUP (2002), 51f.
^"SI brochure (2019)" (PDF). SI Brochure. BIPM. p. 130. Retrieved May 23, 2019.
^"SI brochure (2019)" (PDF). SI Brochure. BIPM. p. 132. Retrieved May 23, 2019.
^"The NIST Reference on Units, Constants, and Uncertainty".
^"2018 CODATA Value: elementary charge". The NIST Reference on Constants, Units, and Uncertainty. NIST. 20 May 2019. Retrieved 2019-05-20.
^"2018 CODATA Value: Faraday constant". The NIST Reference on Constants, Units, and Uncertainty. NIST. 20 May 2019. Retrieved 2019-05-20.
^Martin Karl W. Pohl. "Physics: Principles with Applications" (PDF). DESY. Archived from the original (PDF) on 2011-07-18.
^Hasbrouck, Richard. Mitigating Lightning Hazards Archived 2013-10-05 at the Wayback Machine, Science & Technology Review May 1996. Retrieved on 2009-04-26.
^How to do everything with digital photography – David Huss, p. 23, at Google Books, "The capacity range of an AA battery is typically from 1100–2200 mAh."