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Homework Help: V=kq/d or W=qEd

  1. Jun 16, 2009 #1
    I'm really confused about these two equations; are they the same or do they denote different things?

    I know they are both to do with electric potential, but in what context do I employ them in? Our teacher told us to use one of them in a uniform field and another one of them in a non-uniform field but I don't remember which one is which.

    Thanks in advance.
  2. jcsd
  3. Jun 16, 2009 #2


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    Homework Helper

    No, V is the electric potential (not potential energy) and W is work (energy). The electrical potential energy, not to be confused with the electric potential, is the potential energy a charge has in an electrical field.

    It is similar to gravity, where if you lift an object a short distance h from the ground the object has a potential energy of mgh. The work required to lift that object a distance h is then also mgh. The electric field works the same way. When you move an object away from an electrical charge you have to do work.

    The formula [itex]V=k\frac{q}{d}[/itex] gives the potential at a distance d. This formula is only valid for point charges. The formula [itex]W=qEd[/itex] is the work needed to move a charge q in an electrical field E a distance d. The general formula is W=qV, for a uniform electrical field V=Ed. Therefore you can only use W=qEd for a point charge in a uniform electrical field.
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