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Coulomb
Coulomb  

Unit system  SI derived unit 
Unit of  Electric charge 
Symbol  C 
Named after  CharlesAugustin de Coulomb 
Unit conversions  
1 C in ...  ... is equal to ... 
SI base units  1 A s 
CGS units  Script error: No such module "Gaps". statC 
Atomic units  Script error: No such module "Gaps".^{[1]} 
The coulomb (named after CharlesAugustin de Coulomb, unit symbol: C) is the SI unit of electric charge (symbol: Q or q), defined as the charge transported by a constant current of one ampere in one second:
 <math>1 \text{ C} = 1 \text{ A} \cdot 1 \text{ s}</math>
Thus it is also the amount of excess charge on a capacitor of one farad charged to a potential difference of one volt:
 <math>1 \text{ C} = 1 \text{ F} \cdot 1 \text{ V}</math>
It is equivalent to the charge of approximately 6.241×10^{18} protons, and −1 C is equivalent to the charge of about 6.241×10^{18} electrons.
Contents
Name and notation
This SI unit is named after CharlesAugustin de Coulomb. As with every International System of Units (SI) unit whose name is derived from the proper name of a person, the first letter of its symbol is upper case (C). However, when an SI unit is spelled out in English, it should always begin with a lower case letter (coulomb), except in a situation where any word in that position would be capitalized, such as at the beginning of a sentence or in material using title case. Note that "degree Celsius" conforms to this rule because the "d" is lowercase.— Based on The International System of Units, section 5.2.^{[2]}
Definition
In the SI system, the coulomb is defined in terms of the ampere and second: 1 C = 1 A × 1 s.^{[3]} The second is defined in terms of a frequency which is naturally emitted by caesium atoms.^{[4]} The ampere is defined using Ampère's force law;^{[5]} the definition relies in part on the mass of the international prototype kilogram, a metal cylinder housed in France.^{[6]} In practice, the watt balance is used to measure amperes with the highest possible accuracy.^{[6]}
Since the charge of one electron is known to be about −1.602176565(35)×10^{−19}Lua error: Unmatched closebracket at pattern character 67.,^{[7]} −1 C can also be considered to be the charge of roughly Script error: No such module "Gaps". (or +1 C the charge of that many positrons or protons), where the number is the reciprocal of Script error: No such module "Gaps"..
The proposed redefinition of the ampere and other SI base units would have the effect of fixing the numerical value of the fundamental charge to an explicit constant expressed in coulombs, and therefore it would implicitly fix the value of the coulomb when expressed as a multiple of the fundamental charge (the numerical values of those quantities are the multiplicative inverses of each other).
SI prefixes
#REDIRECTmw:Help:Magic words#OtherThis page is a soft redirect. colspan="7" #REDIRECTmw:Help:Magic words#Other
This page is a soft redirect. Common multiples are in bold face.
Submultiples  Multiples  

Value  Symbol  Name  Value  Symbol  Name  
10^{−1} C  dC  decicoulomb  10^{1} C  daC  decacoulomb  
10^{−2} C  cC  centicoulomb  10^{2} C  hC  hectocoulomb  
10^{−3} C  mC  millicoulomb  10^{3} C  kC  kilocoulomb  
10^{−6} C  µC  microcoulomb  10^{6} C  MC  megacoulomb  
10^{−9} C  nC  nanocoulomb  10^{9} C  GC  gigacoulomb  
10^{−12} C  pC  picocoulomb  10^{12} C  TC  teracoulomb  
10^{−15} C  fC  femtocoulomb  10^{15} C  PC  petacoulomb  
10^{−18} C  aC  attocoulomb  10^{18} C  EC  exacoulomb  
10^{−21} C  zC  zeptocoulomb  10^{21} C  ZC  zettacoulomb  
10^{−24} C  yC  yoctocoulomb  10^{24} C  YC  yottacoulomb 
See also SI prefix.
Conversions
 The magnitude of the electrical charge of one mole of elementary charges (approximately 6.022×10^{23}, or Avogadro's number) is known as a faraday unit of charge (closely related to the Faraday constant). One faraday equals Script error: No such module "Gaps".. In terms of Avogadro's number (N_{A}), one coulomb is equal to approximately 1.036 × N_{A}×10^{−5} elementary charges.
 One amperehour = 3600 C, 1 mA⋅h = 3.6 C.
 The elementary charge is 1.602176565(35)×10^{−19}Lua error: Unmatched closebracket at pattern character 67..^{[7]}
 One statcoulomb (statC), the obsolete CGS electrostatic unit of charge (esu), is approximately 3.3356×10^{−10} C or about onethird of a nanocoulomb.
 One coulomb is the magnitude (absolute value) of electrical charge in Script error: No such module "Gaps". protons or electrons.^{[1]}
Relation to elementary charge
The elementary charge, the charge of a proton (equivalently, the negative of the charge of an electron), is approximately 1.602176565(35)×10^{−19}Lua error: Unmatched closebracket at pattern character 67.^{[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 K_{J} and von Klitzing constant R_{K} are exact defined values (written K_{J90} and R_{K90}), and it follows that the elementary charge e = 2/(K_{J}R_{K}) is also an exact defined value in this unit system.^{[8]} Specifically, e_{90} = (2×10^{−9})/(25812.807 × 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 1.602176487×10^{−19}Lua error: Unmatched closebracket at pattern character 67.",^{[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; the SI definitions are unlikely to change until at least 2015.^{[10]}
In everyday terms
 The charges in static electricity from rubbing materials together are typically a few microcoulombs.^{[11]}
 The amount of charge that travels through a lightning bolt is typically around 15 C, although large bolts can be up to 350 C.^{[12]}
 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.^{[13]}
 According to Coulomb's law, two negative point charges of 1Lua error: Unmatched closebracket at pattern character 67., placed one meter apart, would experience a repulsive +force of 9×10^{9}Lua error: Unmatched closebracket at pattern character 67., a force roughly equal to the weight of Script error: No such module "Gaps". metric tons of mass on the surface of the Earth.
 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 6.24×10^{18}Lua error: Unmatched closebracket at pattern character 67.. 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 through an AA battery, but the total energy transferred by the flow of the lightning's electrons is 300 million times greater.
See also
 Abcoulomb, a cgs unit of charge
 Ampère's circuital law
 Coulomb's law
 Electrostatics
 Elementary charge
 Faraday (unit), an obsolete unit
 Quantity of electricity
Notes and references
 ^ ^{a} ^{b} Script error: No such module "Gaps". is the reciprocal of the 2010 CODATA recommended value Script error: No such module "Gaps". 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} "Watt Balance". BIPM.
 ^ ^{a} ^{b} ^{c} "CODATA Value: elementary charge". The NIST Reference on Constants, Units, and Uncertainty. US National Institute of Standards and Technology. June 2011. Retrieved 20110623.
 ^ ^{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 (2): 71. Bibcode:2005Metro..42...71M. doi:10.1088/00261394/42/2/001.
 ^ Report of the CCU to the 23rd CGPM
 ^ Anon (November 2010). "BIPM Bulletin" (PDF). BIPM. Retrieved 20110128.
 ^ Martin Karl W. Pohl. "Physics: Principles with Applications" (PDF). DESY.
 ^ Hasbrouck, Richard. Mitigating Lightning Hazards, Science & Technology Review May 1996. Retrieved on 20090426.
 ^ 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."
