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: Surface charge density

  1. Jul 11, 2010 #1
    1. The problem statement, all variables and given/known data
    A large plane having uniform charge density has an electric field just outside the plane that points directly toward the plane with magnitude 1.50×10^4 N/C .

    What is the surface charge density?
    Express your answer with the appropriate unit

    2. Relevant equations

    I am not sure how to start this, the relevant equations would probably be enough to get me through this questions.

    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jul 11, 2010 #2
    Right. By Gauss Law electric field of an infinitely large plane non-conducting sheet is σ/2ε where σ is charge density and ε is permittivity of free space.
     
  4. Jul 11, 2010 #3
    thanks for that, what is the permittivity of free space????? also is this meant to be an easy question?
     
  5. Jul 12, 2010 #4
    Permittivity constant accounts the dielectric properties of the medium and for air(or vacuum) it is 8.854×10−12 Fm-1.
    Remember the constant in the Coulomb's Law? It is actually 1/4πε .
    As for the question itself if you are familiar with Gauss law it shouldn't be difficult and the result is used as a standard formula in many texts.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook