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Homework Help: Magnitude of dipole moment

  1. Jan 25, 2010 #1
    1. The problem statement, all variables and given/known data
    A certain electric dipole is placed in a uniform electric field E of magnitude 20 N/C. Figure 22-59 gives the potential energy U of the dipole versus the angle θ between E and the dipole moment P. What is the magnitude of P?

    2. Relevant equations

    3. The attempt at a solution
    Somehow there is an integral needed to solve this but I don't know where to start. there is also a graph with this question.
  2. jcsd
  3. Jan 25, 2010 #2
    i thought...
    [tex]U=-\vec{p} \cdot \vec{E}[/tex]
    but idk if that really changes much.
  4. Jan 26, 2010 #3
    It does, i was just forgetting to multiply it by the factor of 10^-26 hehe. Thanks.
  5. Feb 10, 2011 #4
    can't you just take Us to be the maximum, and the angle of 180 to be the angle that corresponds to the maximum potential, and plug these into U=-pEcos(theta), along with the magnitude of E?
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