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Homework Help: Gauss law

  1. May 10, 2008 #1
    1. The problem statement, all variables and given/known data

    A metal ball with radius R = 0,6 m is charged with Q = 0.15 nC. Find the electrical field as function of the distance r from the center of the ball.

    3. The attempt at a solution

    Gauss law:

    Q = e0*E(r)*A = e0*E(r)*4*pi*R^2

    which gives

    E(r) = Q / e0*4*pi*R^2

    I know that inside the ball, the field will be 0. But obviously this is not a function of r...Am I on the right track?
  2. jcsd
  3. May 10, 2008 #2

    Doc Al

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    Staff: Mentor

    You're fine.

    E(r) = 0 for r<R is perfectly acceptable as a function of r.
  4. May 10, 2008 #3
    And outside the ball? I would expext the field to decrease with increasing r, not be constant...
  5. May 10, 2008 #4

    Doc Al

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    Staff: Mentor

    Right. You have that already done in your first post. (Just change R to r in your equation for E.)
  6. May 11, 2008 #5

    I guess you are correct. The field inside a conductor is zero.

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