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Homework Help: Electrostatics Problem

  1. Dec 2, 2006 #1
    1. The problem statement, all variables and given/known data
    An electron orbits a nucleus which carries a charge of +9.6E-19 C. If the electron's orbit radius is 2.0E-10 m, what is its electric potential energy?

    2. Relevant equations
    Ep = kQ1Q2/r
    V = kQ/r
    V = Ep/Q

    3. The attempt at a solution
    I tried using Ep = kQ1Q2/r
    Ep = (9E9)(9.6E-19C)(-1.6E-19C) / (2.0E-10m)
    Ep = -6.9E-18 J
    the answer key is saying -6.9E-19 J

    and V = kQ/r , V = Ep/Q
    V = (9E9)(9.6E-19C) / (2.0E-10m)
    V = 43.2 V
    V = Ep/Q
    Ep = 43.2 V x (1.6E-19)
    Ep = -6.9E-18 J
    the answer key is saying -6.9E-19 J

    Am I doing something wrong, or is the answer key off by an exponent?

  2. jcsd
  3. Dec 2, 2006 #2
    you seem to be very correct to me

  4. Dec 2, 2006 #3
    ok, thank you
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