Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Quadrupole moment?

  1. Feb 8, 2007 #1
    quadrupole moment??

    The problem basically states that there are three point charges: q, -2q, q, placed along the z-axis at: a, 0, -a. The problem asks to find the monopole moment, dipole moment and quadrupole moment. I've been able to get the first to, but I have no idea how to go about getting the quadrupole moment. Tge prof never really explained it, so can someone please explain what the quadrupole moment matrix is....
  2. jcsd
  3. Feb 9, 2007 #2


    User Avatar
    Homework Helper
    Gold Member

    These links may help

    http://orca.phys.uvic.ca/~tatum/elmag/em3.pdf [Broken] - pdf file
    Last edited by a moderator: May 2, 2017
  4. Feb 10, 2007 #3

    Meir Achuz

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    For a collection of point charges, the quadrupole moment is defined as
    Q=Sum_i{q_i r_i^2 [3cos^2(theta_i)-1]/2}.
    For your case, theta is either 0 or 180.
  5. Feb 11, 2007 #4
    Thank you both:):)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook