Remember how heat is the flow of energy from an object with higher temperature to lower temperature? The flow of heat stops when the two objects reach the same temperature. The same is true for electric energy. Electric energy flows from an area of higher electric potential energy to an area of lower electric potential energy and stops once the electric potential energy in both areas is the same.

Take for example the charged comb that was rubbed with a piece of fur. If the comb comes into contact with the Earth, the charge will flow from the comb into the Earth until the electric potential is equal. In other words, electrons will flow as long as there is a potential difference. This flow of electrons is called an electric current. In this case, the flow will stop quickly because the potential difference gets to zero quickly. To keep an electric current going, there must always be a potential difference so the charges will continue to move.