Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    The charge density is zero for r > 1.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook