coulomb Unit system: SI derived unit Unit of... Electric charge Symbol: C Named after: Charles-Augustin de Coulomb Unit conversions 1 C in... is equal to... SI base units 1 A s CGS units 2997924580 statC Atomic units 6.24150965(16)×1018 e
Name and notation
This SI unit is named after Charles-Augustin de Coulomb. As with every SI unit whose name is derived from the proper name of a person, the first letter of its symbol is upper case (C). When an SI unit is spelled out in English, it should always begin with a lower case letter (coulomb), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius" conforms to this rule because the "d" is lowercase. —Based on The International System of Units, section 5.2. 
In the SI system, the coulomb is defined in terms of the ampere and second: 1C = 1A × 1s. The second is defined in terms of a frequency which is naturally emitted by caesium atoms. The ampere is defined using Ampère's force law; the definition relies in part on the mass of the international prototype kilogram, a metal cylinder housed in France. In practice, the watt balance is used to measure amperes with the highest possible accuracy.
SI multiples for coulomb (C) Submultiples Multiples Value Symbol Name Value 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 not used 1021 C ZC zettacoulomb 10−24 C yC not used 1024 C YC yottacoulomb Common multiples are in bold face.
See also SI prefix.
- 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 is equal to 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 mAh = 3.6 C
- The elementary charge is 1.602176487×10−19 C
- One statcoulomb (statC), the CGS electrostatic unit of charge (esu), is approximately 3.3356×10−10 C or about 1/3 nC.
- One coulomb is the magnitude (absolute value) of electrical charge in 6.24150965(16)×1018 protons or electrons. 
Relation to elementary charge
The elementary charge, the charge of a proton (equivalently, the negative of the charge of an electron), is approximately 1.602176487(40)×10−19 C. 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. 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. Specifically, exactly. SI itself may someday change its definitions in a similar way. 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 1.602176487×10−19 coulomb" This proposal is not yet accepted as part of the SI system: The SI definitions are unlikely to change until at least 2015.
In everyday terms
- The charges in static electricity from rubbing materials together are typically a few microcoulombs.
- The amount of charge that travels through a lightning bolt is typically around 15 C, although large bolts can be up to 350 C.
- The amount of charge that travels through a typical alkaline AA battery is about 5 kC = 5000 C = 1400 mAh. After that charge has flowed, the battery must be discarded or recharged.
- According to Coulomb's Law, two point charges of +1 C, placed one meter apart, would experience a repulsive force of 9×109 N, a force roughly equal to the weight of 920,000 metric tons of mass on the surface of the Earth.
- Abcoulomb, a cgs unit of charge
- Ampère's circuital law
- Coulomb's law
- Elementary charge
- Faraday (unit), an obsolete unit
- Quantity of electricity
- ^ a b c d Mohr, Peter J.; Taylor, Barry N.; Newell, David B. (2008). "CODATA Recommended Values of the Fundamental Physical Constants: 2006". Rev. Mod. Phys. 80: 633–730. Bibcode 2008RvMP...80..633M. doi:10.1103/RevModPhys.80.633. http://physics.nist.gov/cuu/Constants/codata.pdf. Direct link to value. The inverse value (the number of elementary charges in 1C) is given by 1/[1.602176487(40)×10-19] = 6.24150965(16)×1018.
- ^ "SI Brochure, Appendix 1,". BIPM. p. 144. http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf.
- ^ "SI brochure, section 2.2.2". BIPM. http://www.bipm.org/en/si/si_brochure/chapter2/2-2/table3.html.
- ^ "SI brochure, section 184.108.40.206". BIPM. http://www.bipm.org/en/si/si_brochure/chapter2/2-1/second.html.
- ^ "SI brochure, section 220.127.116.11". BIPM. http://www.bipm.org/en/si/si_brochure/chapter2/2-1/ampere.html.
- ^ a b "Watt Balance". BIPM. http://www.bipm.org/en/scientific/elec/watt_balance/.
- ^ a b c d Mills, I. M.; Mohr, P. J.; Quinn, T. J.; Taylor, B. N.; Williams, E. R. (2005). "Redefinition of the kilogram: a decision whose time has come". Metrologia 42: 71. Bibcode 2005Metro..42...71M. doi:10.1088/0026-1394/42/2/001.
- ^ Report of the CCU to the 23rd CGPM
- ^ Anon (November 2010). "BIPM Bulletin". BIPM. http://www.bipm.org/utils/en/pdf/BIPM_Bulletin.pdf. Retrieved 2011-01-28.
- ^ Martin Karl W. Pohl. "Physics: Principles with Applications". DESY. http://www-zeuthen.desy.de/~pohlmadq/teach/112/ch16.pdf.
- ^ Hasbrouck, Richard. Mitigating Lightning Hazards, Science & Technology Review May 1996. Retrieved on 2009-04-26.
- ^ How to do everything with digital photography – David Huss at Google Books, "The capacity range of an AA battery is typically from 1100–2200 mAh."
SI units Base units Derived units Accepted for use
See also Book:International System of Units · Category:SI base units
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