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Electric Potential Energy Concept

  1. Jul 7, 2015 #1
    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. jcsd
  3. Jul 7, 2015 #2
    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).
  4. Jul 7, 2015 #3
    That means all of the points listed are true then? I'm really uncertain about the second point.
  5. Jul 7, 2015 #4
    Your second point is true as long as you offset the potentials of all the charges in the system wrt. the ground you take.
  6. Jul 7, 2015 #5
    what did u end up getting for this?
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