Coulomb is a measure of electric charge and bears the name of Charles-Augustin de Coulomb. The electrons can be treated as an electrical charge, so the coulomb is a count of electrons and is, therefore, a dimensionless unit. The coulomb was the basic unit of measurement until the Institute of Standards (SI) made the amperage the basic unit of measurement in 1960. The coulomb can be easily calculated from the current in an electrical circuit and the time the circuit is closed.

It defines the coulomb as the amount of electric charge that 1 amp carries in a second. This can be expressed as 1C=1As and makes the coulomb equal to approximately 6.24 x 10^18 electrons.

Examine an equivalent definition of coulomb as the charge stored by a farad capacitor with an electric potential of one volt. This can be shown mathematically as 1C x 1F = 1V.

Use the **Definition of Coulomb** to calculate current and time coulombs. Then we have C = from where C is the charge in coulombs, A is the current in amperes and s is the time in seconds.

## Calculate Coulombs

Express the Coulomb law. This is given as F = Ke * q1 * q2 /r^2 where F is the force exerted by charges q1 and q2, Ke is the Coulomb’s constant (8.987 x 10 ^ 9 Nm square/square pinning) and r is the distance separating q1 and q2.