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In [[physics]] and [[chemistry]], the '''Faraday constant''' (named after [[Michael Faraday]]) is the magnitude of [[electric charge]] per [[mole (unit)|mole]] of [[electron]]s.<ref>The term "magnitude" is used in the sense of "[[absolute value]]": The charge of an electron is negative, but ''F'' is always defined to be positive.</ref> It has the currently accepted value | |||
:9.64853399(24) x 10<sup>4</sup> C mol<sup>-1</sup>. | |||
The constant ''F'' has a simple relation to two other physical constants: | |||
:<math>F\,=\,eN_{A}</math> | |||
where | |||
:{{physconst|e|symbol=yes|round=auto|after=;}} | |||
:{{physconst|NA|symbol=yes|round=auto|after=.}} | |||
''N''<sub>A</sub> is the [[Avogadro constant]] (the ratio of the number of particles 'N' to the amount of substance 'n' - a unit mole), and ''e'' is the [[elementary charge]] or the magnitude of the [[electric charge|charge]] of an [[electron]]. This relation is true because the amount of charge of a mole of electrons is equal to the amount of charge in ''one'' electron multiplied by the number of electrons in a mole. | |||
The value of ''F'' was first determined by weighing the amount of [[silver]] deposited in an electrochemical reaction in which a measured [[Current (electricity)|current]] was passed for a measured time, and using [[Faraday's law of electrolysis]].<ref>[http://physics.nist.gov/cuu/Constants/historical1.html NIST Introduction to physical constants]</ref> Research is continuing into more accurate ways of determining the interrelated constants ''F'', ''N''<sub>A</sub>, and ''e''. | |||
==Other Common Units of Faraday's Constant== | |||
* 96,485 J (96.485 kJ) per volt gram equivalent | |||
* 23.061 kcal per volt gram equivalent | |||
* 26.801 A·h/mol | |||
==Faraday unit of charge== | |||
Related to Faraday's constant is the "faraday", a unit of [[electrical charge]]. It is much less common than the [[coulomb]], but sometimes used in electrochemistry.<ref>[http://books.google.com/books?id=r-Qpy0KQayIC&pg=PA51 ''Foundations Of Physics, Volume 2'', by R. S. Gambhir, p51]</ref> One faraday of charge is the magnitude of the charge of one mole of electrons, i.e. {{physconst|F|unit=no|after= [[coulomb|C]].}} | |||
Expressed in faraday's, the Faraday constant F equals "1 faraday of charge per mole". | |||
This faraday unit is not to be confused with the [[farad]], an unrelated unit of [[capacitance]] (1 farad= 1 coulomb/1 volt). | |||
==Popular media== | |||
''[[The Simpsons]]'' episode "[[Dark Knight Court]]" (RABF10) has [[Mr. Burns]] asking [[Comic Book Guy]] how much he wants for his entire comic book inventory. He says "the speed of light expressed as dollars" and Mr. Burns says to Smithers, "give him Faraday's Constant." The check is written for $96,485.34. | |||
==See also== | |||
* [[Faraday cage]] | |||
* [[Faraday efficiency]] | |||
* [[Faraday's law of electrolysis]] | |||
* Faraday's law of [[Electromagnetic induction]] | |||
==References== | |||
{{reflist}} | |||
<!-- Some of these cats may be redundant --> | |||
[[Category:Electrochemistry]] | |||
[[Category:Physical constants]] | |||
[[Category:Michael Faraday]] | |||
[[Category:Units of electrical charge]] | |||
[[Category:Units of amount of substance]] | |||
{{physical-chemistry-stub}} | |||
{{electromagnetism-stub}} |
Revision as of 21:34, 22 November 2013
In physics and chemistry, the Faraday constant (named after Michael Faraday) is the magnitude of electric charge per mole of electrons.[1] It has the currently accepted value
- 9.64853399(24) x 104 C mol-1.
The constant F has a simple relation to two other physical constants:
where
NA is the Avogadro constant (the ratio of the number of particles 'N' to the amount of substance 'n' - a unit mole), and e is the elementary charge or the magnitude of the charge of an electron. This relation is true because the amount of charge of a mole of electrons is equal to the amount of charge in one electron multiplied by the number of electrons in a mole.
The value of F was first determined by weighing the amount of silver deposited in an electrochemical reaction in which a measured current was passed for a measured time, and using Faraday's law of electrolysis.[2] Research is continuing into more accurate ways of determining the interrelated constants F, NA, and e.
Other Common Units of Faraday's Constant
- 96,485 J (96.485 kJ) per volt gram equivalent
- 23.061 kcal per volt gram equivalent
- 26.801 A·h/mol
Faraday unit of charge
Related to Faraday's constant is the "faraday", a unit of electrical charge. It is much less common than the coulomb, but sometimes used in electrochemistry.[3] One faraday of charge is the magnitude of the charge of one mole of electrons, i.e. Template:Physconst
Expressed in faraday's, the Faraday constant F equals "1 faraday of charge per mole".
This faraday unit is not to be confused with the farad, an unrelated unit of capacitance (1 farad= 1 coulomb/1 volt).
Popular media
The Simpsons episode "Dark Knight Court" (RABF10) has Mr. Burns asking Comic Book Guy how much he wants for his entire comic book inventory. He says "the speed of light expressed as dollars" and Mr. Burns says to Smithers, "give him Faraday's Constant." The check is written for $96,485.34.
See also
- Faraday cage
- Faraday efficiency
- Faraday's law of electrolysis
- Faraday's law of Electromagnetic induction
References
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
Template:Physical-chemistry-stub Template:Electromagnetism-stub
- ↑ The term "magnitude" is used in the sense of "absolute value": The charge of an electron is negative, but F is always defined to be positive.
- ↑ NIST Introduction to physical constants
- ↑ Foundations Of Physics, Volume 2, by R. S. Gambhir, p51