What is Coulomb's law of electrostatics?
It describes the amount of force between two electrical charges. The force is actractive if charges are of opposite sign (+ and -), repulsive if charges are of same sign (-- or ++).
The force is modulated by medium between the two charges with a factor called dielectric constant dc and is proportional to product of the two charges Q1 and Q2. The force obviously decrease if distance r between the two charges increase, as the square of the distance: F=(dcQ1Q2)/r^2