And so the positive charge will decrease and the inside will become more negative. At the same time as these potassiums are being pumped into the outside, the outside will gain a certain positive charge. So as the positive charge builds up on the outside, the electric force begins to force the potassium back inside. So we build up our positive charge on the outside, and that drives via an electric force, these potassiums slowly back inside. And eventually when the electric force, due to the positive charge build up on the outside is exactly the same as the force that is pushing our potassiums to the outside. As a result of the concentration gradient, when these two forces are exactly the same and point in the opposite direction, equilibrium is reached.