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Homework Help: Electric Potential Energy of electron orbits

  1. Sep 23, 2008 #1
    An electron and a proton are initially very far apart (effectively an infinite distance apart). They are then brought together to form a hydrogen atom, in which the electron orbits the proton at an average distance of 5.43 * 10-11 m. What is EPEfinal - EPEinitial, which is the change in the electric potential energy?

    I have no idea where to start
     
  2. jcsd
  3. Sep 23, 2008 #2

    LowlyPion

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    Isn't the potential energy given by PE = kq1*q2/r

    If EPE at infinity is 0, then ... The change is ...
     
  4. Sep 23, 2008 #3
    In my notes I have [tex]\Delta E.P.E[/tex] of electron = q(Vb-Va) = (-e)(Vb-Va)

    I am really not getting this


    Im sorry, I might have something here... One minute..
     
  5. Sep 23, 2008 #4
    Okay I am confused
     
  6. Sep 23, 2008 #5

    LowlyPion

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    What is the charge of an electron and a proton?

     
    Last edited: Sep 23, 2008
  7. Sep 23, 2008 #6
    So, would it be...

    (-1.6*10^19)(0 - 5.43 *10^-11)
     
  8. Sep 23, 2008 #7

    LowlyPion

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    It's the product of both charges.

    PE = kq1*q2/r


    And check the exponent of the charges. And don't forget k.
     
  9. Sep 23, 2008 #8
    Okay, so I did PE = [(9*10^9)(-1.6*10^-19)(1.6*10^-19)] / 5.43*10^-11

    My answer is right!!! -4.24 * 10^18

    Thank you
     
  10. Sep 23, 2008 #9

    LowlyPion

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    You're welcome.

    And don't act so surprised. You had it nailed from kqq/r.

    Good luck.
     
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