Electrostatic forces between any two charges depends upon

Electro static force between two charges

$\text{F}\propto {\text{q}}_{\text{1}}{\text{q}}_{\text{2}}$

${\text{q}}_{\text{1}}{\text{q}}_{\text{2}}$- magnitude of two charges

$\text{F}\propto \frac{1}{{\text{r}}^{\text{2}}}$

r – separation between two charges

$\text{F}\propto \frac{{\text{q}}_{\text{1}}{\text{q}}_{\text{2}}}{{\text{r}}^{\text{2}}}$

$\text{F=}\frac{1}{4\pi {\epsilon }_0}\frac{{\text{q}}_{\text{1}}{\text{q}}_{\text{2}}}{{\text{r}}^{\text{2}}}$

${\epsilon }_0\to$permittivity of free space

$\epsilon \to$permittivity of medium

$\text{=}\frac{1}{4\pi \epsilon }\frac{{\text{q}}_{\text{1}}{\text{q}}_{\text{2}}}{{\text{r}}^{\text{2}}}$