 Coulomb

The coulomb is the SI unit of electric charge. A constant electric current of $1\mathrm{A}$ transports $1\mathrm{C}$ in a time of $1\mathrm{s}$; a constant current of $2\mathrm{A}$ for $3\mathrm{s}$ transports $6\mathrm{C}$. The prefix in $1\mathrm{nC}=10^{-9}\mathrm{C}$ explains the much smaller charge scale used in the worked Coulomb's law example. ^[ref]

The coulomb (symbol: C) is the unit of electric charge in the International System of Units (SI). It is defined as the amount of charge that is transported by a constant current of one ampere (A) in one second (s).