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

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

    User Avatar

    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

    User Avatar

    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
    rajxen

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

     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook