Is the potential difference between a point A and a point B equal to negative the potential difference between point B and point A? Or, are they the same?
The potential difference $V$ between two points is the work per unit charge required to move the charge between the two points. The magnitude of the potential difference (work required per unit charge) from A is B is the same as from B to A. But the sign of the change in potential of one is the negative of the other. That is because if a given charge gains electrical potential moving from A to B (gaining electrical potential energy), that same charge loses the same amount of electrical potential moving from B to A (losing electrical potential energy).
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