As has been said, voltage is related to energy and the voltage that must be applied across the conductor to make the electrons move. This energy (W), measured in Joules , is equal to the voltage difference across which the charge moves. So, W=QV. In practical terms, when a voltage is applied across a conductor, this energy QV is equal to the heat energy that is released in the conductor: if we were to measure the total amount of charge moving through (or in or out - they should all be the same) of the conductor then this would be Q.