Coulomb

The coulomb (symbol: C) is the SI unit of electric charge. It is named after Charles-Augustin de Coulomb (1736 to 1806).

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Definition

1 coulomb is the amount of electric charge carried by a current of 1 ampere flowing for 1 second.

<math> C = A \cdot s</math>
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Explanation

The coulomb could in principle be defined in terms of the charge of an electron or elementary charge. Since the values of the Josephson (CIPM (1988) Recommendation 1, PV 56; 19) and von Klitzing (CIPM (1988), Recommendation 2, PV 56; 20) constants have been given conventional values (KJ ≡ 4.835 979×1014 Hz/V and RK ≡ 2.581 280 7×104 Ω), it is possible to combine these values to form an alternative (not yet official) definition of the coulomb. A coulomb is then equal to exactly 6.241 509 629 152 65×1018 elementary charges. Combined with the current definition of the ampere, this proposed definition would make the kilogram a derived unit.

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SI multiples

Multiple Name Symbol Multiple Name Symbol
100 coulomb C      
101 decacoulomb daC 10–1 decicoulomb dC
102 hectocoulomb hC 10–2 centicoulomb cC
103 kilocoulomb kC 10–3 millicoulomb mC
106 megacoulomb MC 10–6 microcoulomb µC
109 gigacoulomb GC 10–9 nanocoulomb nC
1012 teracoulomb TC 10–12 picocoulomb pC
1015 petacoulomb PC 10–15 femtocoulomb fC
1018 exacoulomb EC 10–18 attocoulomb aC
1021 zettacoulomb ZC 10–21 zeptocoulomb zC
1024 yottacoulomb YC 10–24 yoctocoulomb yC

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Conversions

  • One mole of electrons (approximately 6.022×1023, or Avogadro's number) is known as a faraday (actually -1 faraday, since electrons are negatively charged). One faraday equals 96.485 341 5 kC (the Faraday constant). In terms of Avogadro's number (NA), one coulomb is equal to approximately 1.036 × NA ×10−5 elementary charges.
  • one ampere-hour = 3600 C
  • The elementary charge is approximately 160.2176 zC.
  • One statcoulomb (statC), the CGS electrostatic unit of charge (esu), is approximately 3.3356×10-10 C or about 1/3 nC.
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See also