👉 In physics, coulomb is a unit of electric charge that measures the number of electrons in a particular volume. It is defined as 1 Coulomb (C) = 1.602 × 10^-19 C. The symbol for coulomb is C. It can also be expressed in SI units, such as Ampere (A), Joule (J), and Farad (F). For example, 1 Coulomb equals 3.5