Hey, A coulomb is the amount of charge that passes a point through a wire carrying one ampere for one second. Voltage is a measure of electrical potential energy in units of volts or joules per coulomb (energy/charge). Then 1 volt means 1 joule per coulomb; 2 volts mean 2 joules per coulomb, and 5 volts mean 5 joules per coulomb. But what is meant by 2 or 5 volts? If one coulomb contains a set amount of electrons, how can one coulomb have more energy or potential to do work than another coulomb? What is different?