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A nonconducting spherical shell problem

  1. Nov 21, 2008 #1
    A nonconducting spherical shell of inner radius a=2.00 cm and outer radius b = 2.40 cm has (withing its thickness) a positive charge density p = A/r, where A is a constant and r is the distance from the center of the shell. In addition, a small ball of charge q=45.0 fC is located at that center. What value should A have if the electric field in the shell (a[tex]\leq[/tex]r[tex]\leq[/tex]b) is to be uniform?

    I know the answer that A value is 1.79[tex]\times[/tex]10-11. The problem is I don't know how to solve it. I don't even know which equation I should use. I tried to start with E = kq/r2, but what is the value of r. It is not specified where should I calculate.

    Please help.
    Thank you.
  2. jcsd
  3. Nov 21, 2008 #2


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    r can have any value between a and b. It is a variable, with no specific value.

    Do you know what charge the "q" refers to in your equation for E?
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