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Homework Help: Gauss's Law, Sphere (Electric Field

  1. Sep 15, 2011 #1
    1. The problem statement, all variables and given/known data

    See figure attached.

    2. Relevant equations

    3. The attempt at a solution

    I'm extremely confused.

    For r<1,

    The total charge enclosed should always be,

    [itex] \rho \frac{4}{3\epsilon_{0} \epsilon_{r}} \pi r^{3} = \oint _{S} \vec{E} \cdot \vec{dA} = I[/itex]

    The electric field will disperse radially out of the sphere, in the same direction as [itex]\vec{dA}[/itex] so,

    [itex]I = E\oint_{S} dA = 4\pi r^{2}E[/itex]


    [itex]E = \frac{\rho r}{3 \epsilon_{0} \epsilon_{r}}[/itex]

    I'm confused about what is suppose to change in the region r > 1 ?

    Can someone explain?

    Attached Files:

  2. jcsd
  3. Sep 15, 2011 #2


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    The charge density is zero for r > 1.
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