Let's say you put ina battery that's 9 volts. YOu can vary the voltage on the device. Is it changing the battery voltage or the voltage used throughout the system? How can you have a set voltage> THe equation for current goes V/R=I. SO if you have a certian resistanve and current the batteriy can't be at a certain voltage. It would depende on the reseistance and current. Lastly do all wires have the same amount of electrons. Potential energy over COloumbs equalls voltage. FOr a battery maker to know that tany battery has a certain number of volts means there has to be a standard number of COulombs in the wire. Is it the Coloumbs in the wiring or batteryt hat counts to the voltage?