Voltage as the "cause of motion" of charges? I know voltage is defined as the potential energy difference per unit charge between two points A and B. In textbooks they often describe this potential difference as the "cause" of current through a wire. Further, if this potential difference gets high enough, the charges does not even require a wire to get from point A to point B (like lightning). This is what I fail to understand. Shouldn't the coulomb force still be the "cause" of motion for charges? If you increase the distance between two opposite charges, you also increase the voltage between them, but then the coulomb force is reduced, making their pull towards each other less. My question is basically, is a high potential difference enough to cause lightning, and if not, is it really correct to label voltage as the cause of current through a wire?