Coulomb

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Coulomb
Coulomb diagram.svg
Diagram showing 1 coulomb (electric charge carried by a current of 1 ampere during 1 second) and the equivalent number of electrons
General information
Unit system SI
Unit of electric charge
SymbolC
Named after Charles-Augustin de Coulomb
Conversions
1 C in ...... is equal to ...
    SI base units     As
    CGS units     2997924580  statC
    Atomic units    6.241509×1018  e

The coulomb (symbol: C) is the unit of electric charge in the International System of Units (SI). [1] [2] It is defined to be equal to the electric charge delivered by a 1 ampere current in 1 second, with the elementary charge e as a defining constant in the SI. [2] [1]

Contents

Definition

The SI 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, e = 1.602176634×10−19 C. [3] Inverting the relationship, the coulomb can be expressed in terms of the elementary charge: It is approximately 6241509074460762607.776 e and is thus not an integer multiple of the elementary charge.

The coulomb was previously defined in terms of the ampere based on the force between two wires, as 1 A × 1 s. [4] The 2019 redefinition of the 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

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

SI multiples of coulomb (C)
SubmultiplesMultiples
ValueSI symbolNameValueSI symbolName
10−1 CdCdecicoulomb101 CdaCdecacoulomb
10−2 CcCcenticoulomb102 ChChectocoulomb
10−3 CmCmillicoulomb103 CkCkilocoulomb
10−6 CμCmicrocoulomb106 CMCmegacoulomb
10−9 CnCnanocoulomb109 CGCgigacoulomb
10−12 CpCpicocoulomb1012 CTCteracoulomb
10−15 CfCfemtocoulomb1015 CPCpetacoulomb
10−18 CaCattocoulomb1018 CECexacoulomb
10−21 CzCzeptocoulomb1021 CZCzettacoulomb
10−24 CyCyoctocoulomb1024 CYCyottacoulomb
10−27 CrCrontocoulomb1027 CRCronnacoulomb
10−30 CqCquectocoulomb1030 CQCquettacoulomb
Common multiples are in bold face.

Conversions

In everyday terms

Name and history

Charles-Augustin de Coulomb Charles de Coulomb.png
Charles-Augustin de Coulomb

The coulomb is named after Charles-Augustin de Coulomb . As with every SI unit named after 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. [9]

By 1878, the British Association for the Advancement of Science had defined the volt, ohm, and farad, but not the coulomb. [10] 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. [11] 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. [12]

See also

Notes and references

  1. 1 2 International Bureau of Weights and Measures (Dec 2022), The International System of Units (SI) (PDF), vol. 2 (9th ed.), ISBN   978-92-822-2272-0, archived from the original on 18 October 2021
  2. 1 2 BIPM (20 May 2019). "Mise en pratique for the definition of the ampere in the SI". BIPM. Retrieved 2022-02-18.
  3. The International System of Units (PDF) (9th ed.), International Bureau of Weights and Measures, Dec 2022, ISBN   978-92-822-2272-0
  4. "The NIST Reference on Units, Constants, and Uncertainty". NIST. 12 April 2010.
  5. "2022 CODATA Value: Faraday constant". The NIST Reference on Constants, Units, and Uncertainty. NIST. May 2024. Retrieved 2024-05-18.
  6. Martin Karl W. Pohl. "Physics: Principles with Applications" (PDF). DESY. Archived from the original (PDF) on 2011-07-18.
  7. Hasbrouck, Richard. Mitigating Lightning Hazards Archived 2013-10-05 at the Wayback Machine , Science & Technology Review May 1996. Retrieved on 2009-04-26.
  8. 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."
  9. "SI Brochure, Appendix 1" (PDF). BIPM. p. 144. Archived (PDF) from the original on 2006-06-18.
  10. 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."
  11. (Anon.) (September 24, 1881) "The Electrical Congress", The Electrician, 7.
  12. Donald Fenna, A Dictionary of Weights, Measures, and Units, OUP (2002), 51f.