Coulomb's Law

Coulomb's Law gives the equaton for electrostatic forces acting on two particles. For two particles, where particle 1 has charge $q_1$, particle 2 has charge $q_2$, separated by distance $r$, the electostatic force is given as

$$\mathbf{F}=k\frac{q_1{q}_2}{r^2}\hat{r}$$

where $\hat{r}$ is a unit vector that points along the radial axis extending through the two particles and $k$ is the electrostatic constant $\frac{1}{4\pi {ϵ}_0}$, where ${ϵ}_0$ is the permittivitiy constant, and is ${ϵ}_0=8.85\times {10}^{-12}{C}^2/N\cdot m^2$.

The magnitude of the electrostatic force in Coulomb's law becomes

$$F=\frac{1}{4\pi {ϵ}_0}\frac{|q_1||q_2|}{r^2}$$

A coulumb is defined as the charge that flows from 1 ampere of current in one second:

$$1C=(1A)(1s)$$