Question. What is voltage? By which I mean: what is it about an electric current that makes it current at whatever voltage it is at. To state this as a specific question: what is the difference between current of 1 amp in a circuit where the potential difference between the two ends of the circuit is 1 volt and current of 1 amp in a circuit where the potential difference is 2 volts? Elaboration of the question. I think the bit I am confused about is the fact that voltage causes two things. It causes current, ie amps. But it also causes joules per coulomb. Is that right? If there is a circuit of 1 ohm and we put 1 volt accross it we get current of 1 amp and that current has energy of 1 joule per coulomb. If we then double the voltage to 2 volts we get 2 amps but also 2 joules per coloumb. The overall power delivery is therefore 4 times as much. Ie 4 joules per second. What is it about the current that means it has got 2 joules per coulomb instead of 1 joule per coulomb? ... Maybe this is where the water pressure analogy fails. If we were producing water flow in a pipe by water pressure difference between the two ends and then we doubled the pressure. That would double the flow rate. Say we were using the water flow to power something, a wheel for example. Then we would get twice as much wheel turning work done. All this corresponds to the doubling of current in the electrical example. But what is it in the water pressure analogy that corresponds to the increase of joules per coulomb? We wouldn't get four times as much wheel turning work done. ... Sorry if this question is really stupid. I've got nothing more than school level physics. If you can keep your answer untechnical that would be great. Thank you.