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Homework Help: Energy of Configuration

  1. Aug 22, 2005 #1
    A sphere of radius R carries a charge density kr(where k is a constant!).What will be the energy of the Configuration??
  2. jcsd
  3. Aug 22, 2005 #2

    Meir Achuz

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    1. Find the potential phi(r) inside the sphere.
    2. Integrate rho*phi/2 over the volume of the sphere.
    3. The algebra is a bit complicated. I get 35pi^2k^2R^7/72, but check me for errors.
  4. Aug 22, 2005 #3
    Gentleman,Why won't will be find the Potential outside the sphere..
    I am very much perplexed with this Energy term..This is interaction energy
    Pls help logically,i can do the maths involved.!!
    Pls explain the origin of energy and i think we will integrate over whole space...but i don't have clear idea.!
  5. Aug 22, 2005 #4

    Well i got the solution as 4pi*k^2*R^7/21*epsilon!!
    I don't know whether you are correct or me!
  6. Aug 22, 2005 #5


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    The energy is due to the work done in configuring the sphere. Consider the sphere of radius r, and add a layer of thickness dr. Calculate the work dw is required to put this layer of charge. Integrate the work dw over the radius 0 to R. This will be the energy of the configuration
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