The coulomb (symbol: C) is the
1 C = 1 A ⋅ 1 s displaystyle 1~ text C =1~ text A cdot 1~ text s Thus, it is also the amount of excess charge on a capacitor of one farad charged to a potential difference of one volt: 1 C = 1 F ⋅ 1 V displaystyle 1~ text C =1~ text F cdot 1~ text V It is equivalent to the charge of approximately 7018624200000000000♠6.242×1018 (6995103600000000000♠1.036×10−5 mol) protons, and −1 C is equivalent to the charge of approximately 7018624200000000000♠6.242×1018 electrons. Contents 1 Name and notation 2 Definition 3 SI prefixes 4 Conversions 5 Relation to elementary charge 6 In everyday terms 7 See also 8 Notes and references Name and notation[edit]
This SI unit is named after Charles-Augustin de Coulomb. As with every
SI multiples for coulomb (C) Submultiples Multiples Value SI symbol Name Value SI symbol Name 10−1 C dC decicoulomb 101 C daC decacoulomb 10−2 C cC centicoulomb 102 C hC hectocoulomb 10−3 C mC millicoulomb 103 C kC kilocoulomb 10−6 C µC microcoulomb 106 C MC megacoulomb 10−9 C nC nanocoulomb 109 C GC gigacoulomb 10−12 C pC picocoulomb 1012 C TC teracoulomb 10−15 C fC femtocoulomb 1015 C PC petacoulomb 10−18 C aC attocoulomb 1018 C EC exacoulomb 10−21 C zC zeptocoulomb 1021 C ZC zettacoulomb 10−24 C yC yoctocoulomb 1024 C YC yottacoulomb Common multiples are in bold face. See also SI prefix. Conversions[edit] One coulomb is the magnitude (absolute value) of electrical charge in
6.24150934(14)×10^18 protons or electrons.[1]
The inverse of this number gives the elementary charge of
6981160217662079999♠1.6021766208(98)×10−19 C.[7]
The magnitude of the electrical charge of one mole of elementary
charges (approximately 6.022×1023, or Avogadro's number) is known as
a faraday unit of charge (closely related to the Faraday constant).
One faraday equals 96485.3399 coulombs. 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 ∴ 1 mA⋅h = 3.6 C.
One statcoulomb (statC), the obsolete
Relation to elementary charge[edit] The elementary charge, the charge of a proton (equivalently, the negative of the charge of an electron), is approximately 6981160217662079999♠1.6021766208(98)×10−19 C[7]. In SI, the elementary charge in coulombs is an approximate value: no experiment can be infinitely accurate. However, in other unit systems, the elementary charge has an exact value by definition, and other charges are ultimately measured relative to the elementary charge.[8] For example, in conventional electrical units, the values of the Josephson constant KJ and von Klitzing constant RK are exact defined values (written KJ-90 and RK-90), and it follows that the elementary charge e = 2/(KJRK) is also an exact defined value in this unit system.[8] Specifically, e90 = (6991200000000000000♠2×10−9)/(7004258128070000000♠25812.807 × 7005483597900000000♠483597.9) C exactly.[8] SI itself may someday change its definitions in a similar way.[8] For example, one possible proposed redefinition is "the ampere...is [defined] such that the value of the elementary charge e (charge on a proton) is exactly 6981160217648699999♠1.602176487×10−19 coulombs",[9] (in which the numeric value is the 2006 CODATA recommended value, since superseded). This proposal is not yet accepted as part of the SI. In everyday terms[edit] The charges in static electricity from rubbing materials together are typically a few microcoulombs.[10] The amount of charge that travels through a lightning bolt is typically around 15 C, although large bolts can be up to 350 C.[11] The amount of charge that travels through a typical alkaline AA battery from being fully charged to discharged is about 5 kC = 5000 C ≈ 1400 mA⋅h.[12] The hydraulic analogy uses everyday terms to illustrate movement of charge and the transfer of energy. The analogy equates charge to a volume of water, and voltage to pressure. One coulomb equals (the negative of) the charge of 7018624000000000000♠6.24×1018 electrons. The amount of energy transferred by the flow of 1 coulomb can vary; for example, 300 times fewer electrons flow through a lightning bolt than in the discharge of an AA battery, but the total energy transferred by the flow of the lightning's electrons is 300 million times greater. See also[edit] Abcoulomb, a cgs unit of charge Ampère's circuital law Coulomb's law Electrostatics Elementary charge Faraday constant, the number of Coulombs per Mole Quantity of electricity Notes and references[edit] ^ a b 6.24150934(14)×10^18 is the reciprocal of the 2010 CODATA
recommended value 1.602176565(35)×10^−19 for the elementary charge
in coulomb.
^ "SI Brochure, Appendix 1," (PDF). BIPM. p. 144.
^ "SI brochure, section 2.2.2". BIPM.
^ "SI brochure, section 2.2.1.3". BIPM.
^ "SI brochure, section 2.2.1.4". BIPM.
^ a b "
v t e SI units Authority:
Base units ampere candela kelvin kilogram metre mole second Derived units with special names becquerel coulomb degree Celsius farad gray henry hertz joule katal lumen lux newton ohm pascal radian siemens sievert steradian tesla volt watt weber Other accepted units astronomical unit bar dalton day decibel degree of arc electronvolt hectare hour litre minute minute of arc neper second of arc tonne atomic units natural units See also Conversion of units Metric prefixes Proposed redefinitions Systems of measurement |