Coulomb

The coulomb (unit symbol: C) is the International System of Units (SI) unit of electric charge. It is the charge (symbol: Q or q) transported by a constant current of one ampere in one second:

Thus, it is also the amount of excess charge on a capacitor of one farad charged to a potential difference of one volt:

It is equivalent to the charge of approximately 7018624200000000000♠6.242×10¹⁸ (6995103600000000000♠1.036×10⁻⁵ mol) protons, and −1 C is equivalent to the charge of approximately 7018624200000000000♠6.242×10¹⁸ electrons.

Name and notation

This SI unit is named after Charles-Augustin de Coulomb. As with every International System of Units (SI) unit named for 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.