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Homework Help: Electric potential energy and electric potential.

  1. Aug 24, 2009 #1
    1. The problem statement, all variables and given/known data

    I've just come across a lot of concept questions about electric potential energy and electric potential, and I can't differentiate between the two really. I know electric potential is also called voltage.

    Here's one question for example:
    How can electric potential be high when electric potential energy is relatively low?

    3. The attempt at a solution

    Electric potential only involves one charge, and electric potential energy involves two charges, right? That's all I've got. >.<
  2. jcsd
  3. Aug 24, 2009 #2

    Chi Meson

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    Potential is a quantity (or quality) of a position in space.

    Potential energy is a quantity of an object in that position of space.

    That is, a position will have a certain potential, say 15 V. That means any charge placed there will have 15 joules of potential energy for each coulomb of net charge for the object. A volt is equivalent to a "joule per coulomb." Notice how that basically is the same as the formula V=E/q , which is what defines the potential of any location.

    An object of greater net charge will have more electric potential energy when placed in that same position.

    So in what manner can you have a position at great potential, but an object with low potential energy?
    Last edited: Aug 24, 2009
  4. Aug 24, 2009 #3
    So if you had a relatively small charge in a very powerful space, then the electric potential would be high and the electric potential energy would be low?
  5. Aug 24, 2009 #4

    Chi Meson

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    Essentially, yes. But don't call it "powerful," because power is a different thing. A high potential can be caused by being NEAR a large point charge. The potential of the space surrounding a point charge,Q, is (V=kQ/d). So when you put a second charge,q, in the vicinity of the first charge, the second charge will have potential energy of E=qV = kQq/d .

    Notice that ultimately it doesn't matter which of the two charges you consider "first" or "second."
  6. Aug 24, 2009 #5
    thanks :)

    and sorry about the "powerful" thing, I just wasn't sure about what word to use.
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