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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

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

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:

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.^{[citation needed]}

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!

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 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.

• 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 (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 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.

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

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