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Homework Help: Find the Electric Field

  1. Sep 18, 2011 #1
    I have an exam on Monday in my E&M class. I've been doing the homework, etc etc. My prof. even has a link on his website that has old exams that we can use to study from. The exam Im practicing off of has the questions, a (sketchy) calculation, and an answer. This question has been driving me and my classmates NUTS! Nobody can solve it! I can't make sense of his calculations, can somebody please tell me Im not crazy…or, better yet…show me what Im not seeing. Thanks.


    That weird looking thing at the top that looks like R**(2.3) is supposed to be the radius to the power of 2.3. Yeah, I don't get it either, but thats what my prof. told me.

    The answer is in parenthesis.

    Is there something wrong with the calculations?

    Why can't I figure this out??
  2. jcsd
  3. Sep 18, 2011 #2


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    Staff: Mentor

    Rewriting this, in case you don't understand it: you have a spherical volume filled with distributed static charge. It's not uniformly distributed, it gets more dense the farther you move away from the centre. The charge density in the sphere is a function of distance from the centre=(5.5*10-15)*r2.3

    I've forgotten how to solve these. :redface: I guess it's going to involve an integral.
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