Welcome to the MedLibrary.org Wikipedia Supplement on Coulomb -- Please Click to Return to Front Page

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

Contents 1 Definition 2 Explanation 3 Historical note 4 SI multiples 5 Conversions 6 See also 7 References

Definition

1 coulomb is the amount of electric charge transported in 1 second by a steady current of 1 ampere.^{1 23}

One coulomb is the amount of charge stored by a capacitance of one farad charged to a potential difference of one volt:

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 (K_J ≡ 4.835 979×10¹⁴ Hz/V and R_K ≡ 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.

In everyday situations, positive and negative charges are usually balanced out. According to Coulomb's Law, two point charges of +1 C, one meter apart, would experience a repulsive force of 9×10⁹ N, roughly the equivalent of 900,000 metric tons of weight.

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 made the ampere the base unit. ⁴

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 96485.3399 coulombs (the Faraday constant). In terms of Avogadro's number (N_A), one coulomb is equal to approximately 1.036 × N_A ×10⁻⁵ elementary charges.

• one ampere-hour = 3600 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.

• 1 coulomb is the amount of electrical charge in 6.241506×10¹⁸ electrons or other elementary charged particles.

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 uppercase (C). When an SI unit is spelled out in English, it should always begin with a lowercase 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.

See also

• Abcoulomb, a cgs unit of charge
• Statcoulomb, a cgs unit of charge
• Faraday (unit), an obsolete unit
• Coulomb's law
• Current (electricity)
• Faraday constant
• Quantity of electricity
• SI
• Ampere
• Ampère's circuital law
• Farad

References

1. ^ BIPM Table 3
2. ^ NIST: Table 3. SI derived units with special names
3. ^ BIPM SI Brochure, Appendix 1, p. 144
4. ^ Kowalski, Ludwik, "A Short History of the SI Units in Electricity", pp. 97-99 vol 24, The Physics Teacher, Feb 1986

1.Kowalski, Ludwik, "A Short History of the SI Units in Electricity", pp. 97-99 vol 24, The Physics Teacher, Feb 1986

Wikipedia content modification information:

• This page was last modified on 20 November 2008, at 19:10.

Wikipedia Authorship and Review

Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.

Wikipedia Usage Guidelines

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Coulomb".

The URL for this specific entry is:

• http://medlibrary.org/medwiki/Coulomb

All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.