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Homework Help: Charge distribution, quadrupole

  1. Oct 30, 2012 #1
    1. The problem statement, all variables and given/known data

    Show that, if a charge distribution  has cylindrical symmetry, then knowing the value
    of Qzz allows you to determine the entire quadrupole moment matrix.

    2. Relevant equations

    Tr Q=0, ie Qxx+Qyy+Qzz=0

    3. The attempt at a solution

    Because of the cylindrical symmetry, the charge density changes as a function of ρ, where ρ=(x^2+y^2)^1/2. Then I don't really know where to go from there.
  2. jcsd
  3. Oct 30, 2012 #2
    I have now worked out all values for the quadrupole matrix, I just need to calculate what Qzz is. If anyone can help that would be really useful. Also I realised I made a mistake above, cylinrical symmetry means that it is dependent only z only.
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