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Coulomb

From Academic Kids

The coulomb, symbol C, is the SI unit of electric charge, and is defined in terms of the ampere: 1 coulomb is the amount of electric charge (quantity of electricity) carried by a current of 1 ampere flowing for 1 second. It is also about 6.241506×1018 times the charge of an electron. It is named after Charles-Augustin de Coulomb (1736-1806).

Contents

Alternate definition

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, it is possible to combine these values (KJ ≡ 4.835 9791014 Hz/V and RK ≡ 2.5812807104 Ω) to form an alternate (not yet official) definition of the coulomb. Very simply, a coulomb is then equal to exactly 6.241509629152651018 elementary charges.

A wrong definition

It is sometimes incorrectly said that a coulomb is defined as one mole of electrons (approximately 6.022×1023, or Avogadro's number). This is completely wrong. One mole of electrons is known as a faraday. Just as the ampere and second were defined well before the electron's charge was known, the kilogram was defined well before the mass of the amu was known. Neither value has anything to do with the other. In terms of Avogadro's number (NA), a coulomb is equal to approximately 1.036 × NA × 10-5 elementary charges.

SI electricity units

Template:SI electromagnetism units

See also

cs:Coulomb da:Coulomb de:Coulomb (Einheit) fr:Coulomb (unit) id:Coulomb it:Coulomb hu:Coulomb (egysg) nl:Coulomb ja:クーロン pl:Kulomb pt:Coulomb ru:Кулон sl:Coulomb sr:Кулон fi:Coulombi sv:Coulomb zh:库仑

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