Consider two particles A and B having equal charges and placed at some distance. The particle A is slightly displaced towards B. Does the force on B increase as soon as the particle A is displaced? Does the force on the particle An increase as soon as it is displaced?
Yes, the force on particle B as well as particle A will increase when particle is A is displaced towards particle B.
By Coulomb’s Law, Electric force is inversely proportional to the square of the distance between the two charges.
F α 1/r2
Thus, when A is displaced towards B, the distance between them decreases and hence the force on both the particles will increase.