What does coulomb mean?
The coulomb is the standard international (SI) unit of electric charge, abbreviated C and named after the French physicist Charles-Augustin de Coulomb, a pioneer of electrostatics. One coulomb corresponds to the quantity of electricity conveyed by a steady current of one ampere flowing for one second — an enormous number of individual electrons, roughly six billion billion of them. In practical terms, engineers and physicists use the unit to quantify how much electric charge a battery stores or moves, to describe static discharges such as lightning, and to express fundamental constants like the charge of a single electron, which is about 1.6 × 10⁻¹⁹ coulombs. Although rarely spoken aloud outside laboratories and classrooms, the coulomb underpins much of modern electrical science: relationships such as Ohm's law and Coulomb's law of electrostatic force are routinely stated in terms of it. Its name, like all SI eponymous units, is always lowercase when written out, while its symbol remains capitalized.
nounThe SI derived unit of electric charge, equal to the charge transported by a constant current of one ampere in one second; symbol C.
- The SI unit of electric charge, defined as the charge carried by a current of one ampere flowing for one second.
"A typical lightning bolt transfers several tens of coulombs between cloud and ground."
"The battery delivered about 5,400 coulombs before needing a recharge."
"Since current is charge per unit time, one ampere equals one coulomb per second."
Regular pluralization applies; the abbreviation C remains unchanged in the plural (e.g. '500 C', not '500 Cs').
"The capacitor stored nearly two thousand coulombs of charge."
One coulomb is about 6.24 quintillion electrons — yet it's roughly the charge you feel from a static shock off a doorknob.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of coulomb
The word coulomb is an eponym adopted into English from the name of Charles-Augustin de Coulomb (1736–1806), the French physicist who formulated Coulomb's law describing the force between electric charges. As a unit of measurement it was established internationally in the late 19th century alongside the ampere and other electrical units formalized by early standards bodies. Interestingly, the surname itself traces back through French to the Latin columba, meaning 'dove' or 'pigeon', making the unit distantly related to words like columbine.
How coulomb is actually used
A technical term used mainly in physics and electrical engineering; in everyday speech, charge is usually described indirectly through amperes or watt-hours. It is a named unit and takes the symbol C, capitalized because it honours Charles-Augustin de Coulomb.
Easily confused with coulomb
A column is a vertical pillar or an arranged list, while a coulomb is a unit of electric charge; the two merely resemble each other in spelling.
A volt measures electric potential difference, whereas a coulomb measures electric charge itself.