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Homework Help: Polarisation on the surface of a sphere

  1. Jan 31, 2007 #1
    I am trying to answer a question that states:
    There is a sphere of radius R centred at the origin with a polarisation P = C(xi+yi+zk), where C is a constant, at the surface. What is the total charge in the sphere if there is no net charge?

    I know that P= Nqd where N is the number of charges, q is the charge on each one, and d is the separation distance in the dipoles. But I do not see how to relate this to the sphere in the question. I do not know of any individual charges in the sphere or of any dipoles, or should I be taking these as atoms?
    Any pointers in the right direction would be much appreciated.
  2. jcsd
  3. Feb 1, 2007 #2


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    Homework Helper
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    The collection of dipoles leads to formation of bound charges on the surface and within the material.

    So, to calculate the total charge, you need to apply Gauss's law for a dielectric.

    For additional material try,
    - http://www.du.edu/~jcalvert/phys/polariza.htm - The influence of matter on the electric field
    - Chapter 4 (3rd edition), Introduction to Electrodynamics, David J Griffiths
    Last edited: Feb 1, 2007
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