# Electric Potential Energy Concept

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1. Jul 7, 2015

### r0306

I'm unsure if the following is true or not in the absence of external forces:
• Electric potential is a scalar quantity.
This I know is true because there is no direction associated with potential energy.
• It is always possible to assign a value of zero to the electric potential at the origin.
This I am completely unsure of though I think it is true because potential depends on a reference point that you can set yourself.
• The change in a particle's potential energy depends on the total length of its path between two points.
I suspect that this is true because U = qV and V is dependent on the distance between the points.
• The work required to move a charge q from a point at potential Vi to a point at potential Vf is q(Vf - Vi).
This should be false because (delta)U = q(Vf - Vi) and W = -(delta)U so it should be -q(Vf - Vi) instead.

Can someone please verify my reasoning and correct me if I'm wrong? Thank you.

2. Jul 7, 2015

### TESL@

q(Vf - Vi) is correct for the work done by the force opposing the electric force. If the work done by electric field was being considered, it would be q(Vi - Vf).

3. Jul 7, 2015

### r0306

That means all of the points listed are true then? I'm really uncertain about the second point.

4. Jul 7, 2015

### TESL@

Your second point is true as long as you offset the potentials of all the charges in the system wrt. the ground you take.

5. Jul 7, 2015

### ninipanini

what did u end up getting for this?