The equation for calculating the electrical force between the two charges is given by Coulomb's law
F=\frac{k q1 q2}{r^{2}}
K=constant= 9 x 10⁹ N m²/C²
q1= charge on first particle
q2= charge on second particle
r= distance between the two charges
Greater is the magnitude of the charges, greater will be the force between the two charges. The force is inversely proportional to the square of the distance between the charges.