1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Surface Charge Density and electron

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

    an electron with mass m = 9.11 x 10^-31 is released at rest near a very large positively charged non-conducting charged sheet lying horizontally. What should the surface charge density on this sheet be to keep the electron balanced at rest above the ground? Is it above or below the sheet?

    2. Relevant equations

    F = qE
    d(density) = Eϵ

    3. The attempt at a solution


    qE = mg
    E = (mg)/ q

    d = Eϵ
    d = (mgϵ )/q

    When I plug in all my values I get 4.938 x 10^-22 C/m^2

    but the answer is 9.88 x 10^-22 (if I multiply my answer by 2 it would be right but I dont think thats how I need to do it.)
     
  2. jcsd
  3. Oct 1, 2008 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi grouchy! :smile:

    I'm not sure what you've done, but I think you've used the equation for a point (or nearly point) charge.

    This is a spread-out charge, so you'll have to integrate over the whole plane. :smile:
     
  4. Oct 1, 2008 #3
    I found my mistake, I used the equation for conducting sheet of charge E = d/ϵ

    but the problem says non conducting which is E = d/2ϵ which tells me its right when I multiply by 2 :)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Surface Charge Density and electron
  1. Surface Charge Density (Replies: 17)

  2. Surface charge density (Replies: 1)

Loading...