Assignment:
Consider a positive point charge.
i) Give an example of how you might place two other point charges so that the net force on the initial charge is zero.
ii) If the net force on the charge is zero then this charge is in equilibrium. The equilibrium will be stable if, when the charge is displaced slightly in any direction from its position of equilibrium, there is a force pushing it back toward the equilibrium position. Sketch the necessary electric field for this to be the case.
iii) Show, using Gauss' law, that this is not possible for a distribution of surrounding charges.