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Homework Help: Flux through various Gauss' surfaces

  1. Feb 3, 2015 #1
    1. The problem statement, all variables and given/known data

    I have uploaded a file that shows the question.

    2. Relevant equations

    I believe the only relevant equation is: flux = Q(enclosed)/E(knot)

    3. The attempt at a solution

    Well I have some questions first. The problem statement says that the sphere on the left has a net charge Q. I was under the assumption that all of the charge for a conducting sphere would be located on the outside of the sphere is this true? Does it matter that the sphere is made of a conducting vs insulating material? My attempt:

    A- No flux because no charge is enclosed.
    B- (Q/2)/E(knot)

    Now for the second sphere (the insulating material). Here I am not sure what the difference is as I said before. I know that if the question were regarding charge then I would need to deal with density. However, the question is about flux, so I guess my question is this: In an insulating material is the charge Q evenly distributed throughout the sphere? Or can I still say:

    D- Zero
    E- (Q/2)/E(knot)

    As for C, I am not sure what to do with C.


    Attached Files:

  2. jcsd
  3. Feb 3, 2015 #2


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    You'll want to assume that the charge is distributed uniformly through the insulating sphere. Work using that assumption. You won't be able to compute the charge in C exactly, you just need to figure out whether it's greater or less than the others.
  4. Feb 3, 2015 #3
    Okay so how does this sound:


    I was trying to think about D and C. Correct me if I am wrong but I think there volume is equal.
  5. Feb 3, 2015 #4


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    Sounds ok to me.
  6. Feb 3, 2015 #5
    Sorry I correct my post to late so is it going to be:

    E=B>D>C>A or are D and C equal?
  7. Feb 3, 2015 #6


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    Why would you think D and C are equal?
  8. Feb 3, 2015 #7
    Well if V of the larger circle is 4/3pR^3
    Yeah I don't anymore sorry I wasn't thinking straight :D Thanks for your help!
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