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coulomb

  ('lŏm', -lōm') pronunciation
n. (Abbr. C)

The meter-kilogram-second unit of electrical charge equal to the quantity of charge transferred in one second by a steady current of one ampere.

adj. also cou·lom·bic (kū-lŏm'bĭk, -lōm'-)

Of or relating to the Coulomb force.

[After Charles Augustin de COULOMB.]


 
 

informal, coulomb

[Etymology: C. A. de Coulomb; France 1736-1806] quantity of electricity, electric charge. Symbol C. The coulombs of electricity transported or of charge delivered by a steady current equal the product of current in amperes and time in seconds. But the Coulomb was defined as a base unit for the e.s.u. system.

SI, Metric-m.k.s. = s·A. The following are among the coherent derived units:

C·m-2 for electric flux density, surface density of charge, electric polarization;
C·m-3 for volumic charge, charge density;
C·kg-1 for exposure to X- or gamma-rays;
C·V = joule for energy, work, quantity of heat;
C·V-1 = farad for electric capacitance.

This coulomb is equatable with 6.241 45~ × 1018 electrons.

Metric-c.g.s. See abcoulomb; statcoulomb. See also practical unit.

History

The name ‘coulomb’ was agreed, along with related units and the use of the c.g.s. system, in 1881 at the first International Electrical Conference,
[Nature Vol. 24, 512 (1881)] as the ‘quantity of electricity defined by the condition that an ampère gives one coulomb per second’, with the implication that there be both an absolute form and a corresponding practical unit. The former, later discriminated as the abcoulomb, falls within the e.m.u. system, and is fundamentally definable in terms of purely mechanical units. The practical coulomb = 10-1 abcoulomb.

The creation of explicit laboratory specifications of the ampere, ohm, and volt, which were subsequently found to be slightly discrepant from what was intended, gave a slightly altered coulomb as a unit derived from them. The IEC of 1908 covered the discrepancy by adopting the distinct name international coulomb. Because of experimental vagaries, the value for conversions is normally referred to as the mean international coulomb, = 0.999 85~ C. There is also the US international coulomb, = 0.999 835~ C.

With the implementation of the Metric-m.k.s.A. system in 1948, and its basing of electrical units on an ampere compatible with the original absolute units, the modern coulomb became essentially the old practical coulomb. Sometimes called the absolute coulomb, this became identically the coulomb of the SI.

Since quantity of electricity or electric charge is inherently a count of electrons (or equivalently charged particles), the logical practice would be to define the coulomb from the electron, then the volt from coulomb, rather than the existing reverse practice. Were the electromagnetic units being created afresh today, the coulomb would likely be the charge of 1018 electrons, i.e. 0.160 2~ of the extant coulomb.

 
('lŏm) [for C. A. de Coulomb], abbr. coul or C, unit of electric charge. The absolute coulomb, the current U.S. legal standard, is the amount of charge transferred in 1 second by a current of 1 ampere; i.e., it is 1 ampere-second.


 

1. the unit of electrical charge, defined as the quantity of electrical charge transferred by 1 ampere in 1 second. Symbol C.
2. the SI unit of exposure to radiation. 1 coulomb per kilogram = 3876 roentgen; abbreviated C/kg.

 

To convert from coulombs to:

statcoulombs, multiply by 2.998E+09.
faradays, multiply by 1.036E-05.

Convert:  Into: 
Result: 
Related measurements:
coulombs/sq.cm
coulombs/sq. inch
coulombs/sq. meter


 

Unit of electric charge. A negative coulomb charge consists of 6.24 × 1018 electrons.


 
Wikipedia: coulomb

The coulomb (symbol: C) is the SI unit of electric charge. It is named after Charles-Augustin de Coulomb.

Definition

1 coulomb is the amount of electric charge transported by a current of 1 ampere in 1 second.

1 \,\mathrm{C} = 1 \,\mathrm{A} \cdot 1 \,\mathrm{s}

It can also be defined in terms of capacitance and voltage, where one coulomb is defined as one farad of capacitance times one volt of electric potential difference:

1 \,\mathrm{C} = 1 \,\mathrm{F} \cdot 1 \,\mathrm{V}

Explanation

In principle, the coulomb could be defined in terms of the charge of an electron or elementary charge. 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 (KJ ≡ 4.835 979×1014 Hz/V and RK ≡ 2.581 280 7×104 Ω), it is possible to combine these values to form an alternative (not yet official) definition of the coulomb. A coulomb is then equal to exactly 6.241 509 629 152 65×1018 elementary charges. Combined with the present definition of the ampere, this proposed definition would make the kilogram a derived unit.

If two point charges of + 1 C are held one meter away from each other, the repulsive force they will feel is given by Coulomb's Law as 8.988×109 N [1]. This is roughly equal to the gravitational force of 900,000 metric tons of mass at the surface of the Earth; in everyday terms, it's enough force to accelerate an Airbus A380 airplane up to a final speed of 76,857 km/h in 1 second. In everyday life, most things don't have a large surplus of charge!

Historical note

The ampere was historically a derived unit - being defined as 1 coulomb per second. Therefore the coulomb, rather than the ampere, was the SI base electrical unit.

In 1960 the SI system made the ampere the base unit. [1]

SI multiples


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 zeptocoulomb 1021 C ZC zettacoulomb
10–24 C yC yoctocoulomb 1024 C YC yottacoulomb
Common multiples are in bold face.


Conversions

  • The electrical charge of one mole of electrons (approximately 6.022×1023, or Avogadro's number) is known as a faraday (actually –1 faraday, since electrons are negatively charged). One faraday equals 96.485 341 5 kC (the Faraday constant). In terms of Avogadro's number (NA), one coulomb is equal to approximately 1.036 × NA ×10−5 elementary charges.
  • The elementary charge is approximately 160.2176 zC.
  • One statcoulomb (statC), the CGS electrostatic unit of charge (esu), is approximately 3.3356×10-10 C or about 1/3 nC.
  • 1 coulomb is the amount of electrical charge in 6.241506×1018 electrons or other elementary charged particles.
  • The charge of one electron is equal to -1.6022×10-19 C


This SI unit is named after Charles-Augustin de Coulomb. As for all SI units whose names are derived from the proper name of a person, the first letter of its symbol is uppercase (C). But when an SI unit is spelled out, it should always be written in lowercase (coulomb), unless it begins a sentence or is the name "degree Celsius".
— Based on The International System of Units, section 5.2.

See also

References

  1. ^ Kowalski, Ludwik, "A SHORT HISTORY OF THE SI UNITS IN ELECTRICITY" pp 97-99 vo 24, The Physics Teacher, Feb 1986

Kowalski, Ludwik, "A SHORT HISTORY OF THE SI UNITS IN ELECTRICITY" pp 97-99 vo 24, The Physics Teacher, Feb 1986


 
 

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Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
Measures and Units. A Dictionary of Weights, Measures, and Units. Copyright © Donald Fenna 2002, 2004. All rights reserved.  Read more
Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Answers Corporation Unit Conversions. © 1999-2008 by Answers Corporation. All rights reserved.  Read more
Electronics Dictionary. Copyright 2001 by Twysted Pair. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Coulomb" Read more

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