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Homework Help: Electric Field of a Charged Spherical shell

  1. Jan 31, 2007 #1
    1. The problem statement, all variables and given/known data

    A solid conducting sphere of radius 2.00 cm has a charge 6.70 µC. A conducting spherical shell of inner radius 4.00 cm and outer radius 5.00 cm is concentric with the solid sphere and has a charge -3.50 µC. Find the electric field at the folowing radii from the center of this charge configuration.

    a) r = 3 cm
    b) r = 7 cm

    2. Relevant equations

    E = Q(inside) / (4 * pie * Eo * r^2)

    Eo = 8.85 * 10^ -12

    3. The attempt at a solution

    Q(inside) is just 6.7 uc - 3.5 uc = 3.2 uc

    I just plug in r to the equation to solve for E

    It's wrong, please give me some hints. Thank You
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jan 31, 2007 #2
    that Q inside you calculated...

    would you that value of Q in both questions??

    remember enclosed charge
  4. Jan 31, 2007 #3


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    Homework Helper

    Gauss's Law: [tex]\int_\text{closed surface} \vec E. d\vec S = q_\text{enclosed}/\epsilon_0[/tex]
  5. Jan 31, 2007 #4
    Ohh I understand it now, thank you very much
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