Is voltage just the difference in the density of electrons between two points on a conducting wire? If an atom has an electron in it's valence shell, and it's negatively charged, it's going to be in an elevated energy state. The atom doesn't want to remain in that elevated energy state, so it's going to want to transfer it's energy to whichever atom is open to being placed in a higher energy state. Current will naturally flow from a point of high potential to a point of low potential. This especially makes sense with the water pressure analogy. A one-gallon container filled with water to a pressure of two atmospheres is going to have more water in it than a one-gallon container filled with water to a pressure of one atmosphere, and if you were to connect the two containers, water would naturally come rushing in from the container with a pressure of two atmospheres. In a DC circuit, the point that has the higher density of electrons is going to be the negative point, and the point that has the lower density of electrons is going to be the positive point.

Amperage is the rate of movement of electrons within a circuit, with coulombs representing the number of electrons being moved, and voltage is the difference in the density of electrons between two points on a circuit. If I'm correct, does this mean that there is a maximum achievable voltage in nature? If every single atom within one point on a conducting wire has it's valence shell filled up, and if every single atom within the other end has it's valence shell empty, would this achieve maximum voltage?