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About electric potential

  1. Jun 7, 2010 #1

    I am sure this is very basic but i am struggling to derive or work this out, and i have looked, on the internet and text books and can't find this.

    The electric potential at a point is defined as the work done per unit charge to move a small test charge from infinity to that point.

    And an equation for it is : EP = k*(Q/R)

    I want to get back to the definition from this equation, but i cant get very far:

    here is what i have done: WD= work done

    Q/R = (wd/v)/R
    = wd/vR

    But i can't go much further without it just going back to the original form.... Can anyone help me?

  2. jcsd
  3. Jun 7, 2010 #2


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    hi ojsimon! :smile:

    (what's v ? :confused:)

    work done = ∫ force d(distance) = ∫R kQ/r2 dr :wink:

    (and d(work done)/dr = force)
  4. Jun 7, 2010 #3
    sorry v was meant to be voltage and came from the equation v=wd/q

    Thanks although i don't quite understand your integral?

  5. Jun 7, 2010 #4


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    The integral is the force integrated from infinity to the distance R, since the PE is the work done to get the charge from infinity to R.
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