What potential difference actually means

[franjo]

Does potential difference only indicate how much energy each coulomb have, or make current flow, or do both?

 

[BvU]

A potential difference is a measure for the amount of energy it takes (or yields) to move a unit charge from the one place to the other.

A potential difference (actually, the derivative of a potential) is a measure for the force a unit test charge experiences.

Current is (net) motion of charge.

 

[conscience]

A potential difference (actually, the derivative of a potential) is a measure for the force a unit test charge experiences.

Electric Field

 

[Dale]

Does potential difference only indicate how much energy each coulomb have, or make current flow, or do both?

Potential difference, by itself, does not make current flow. Consider a charged capacitor, there is a potential difference but no current.

 

[sophiecentaur]

I never understand why "Joules per Coulomb is Potential Difference" gives people so much difficulty.
Perhaps it's something to do with the fact that people look at an electric circuit and they seem more concerned with how the charges flow through the wires in a simple, ideal circuit than what goes on in the resistor or the battery. Wires, in practice, are chosen to be fat enough and short enough that very few Joules are dissipated for every Coulomb that passes through them. (That ensures that nearly all the Energy gets from the source to the load.) In an electric toaster, the element wires are specially chosen to have a much higher resistance than the supply leads so the Potential Difference across the actual element is very nearly the whole supply Volts.
I could blame that danged Water Flow Model which doesn't help in the slightest to help the student in that respect.