• Question: could you please explain why a concentration of electrons can produce an instantanious di pole?

    Asked by oshkar to Ben, Clare, Ezzy, Mario, Sam on 10 Mar 2012.
    • Photo: Mario Campanelli

      Mario Campanelli answered on 9 Mar 2012:

      a concentration of charges will be characterised by its total charge, Q and all successive moments, namely dipole, quadrupole, octupole etc., reflecting the space distribution of these charges. A perfect dipole with no net charge is just made of a positive and negative charge separated by some distance d; if instead of, say, a proton and an electron, with a charge density 2e, we have and electron instead of the proton and three electrons instead of the initial one, we have a situation where the charge density is still 2e, but the net charge will be -4e; in any case, we have created a dipole out of four electrons, and no positive charges.

    • Photo: Ben Smart

      Ben Smart answered on 10 Mar 2012:

      Imagine all the electrons are close together in a small blob (this blob is your concentration of electrons). These electrons wont be sitting still, they’ll be whizzing about, but they will still be together in their little blob. Now at any one moment, the electrons might all happen to move over to one side of the blob (they’re all whizzing about randomly, so this can happen). If there are more electrons at one side of the blob than the other side, then the side of the blob with lots of electrons will have lots of negative electrical charge (electrons have a negative electrical charge). The side of the blob with very few electrons will have very little negative electrical charge. So now you have a blob with lots of negative electrical charge on one side of it, and less negative charge on the other side of it. That is a dipole! So at that instant in time you have an instantanious dipole 🙂 Hope this answers your question, if it’s not clear, just ask some more and I’ll try to help!

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