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Find electric Field through 3 plates using Gausses Law

  1. Feb 13, 2013 #1
    1. The problem statement, all variables and given/known data
    The figure shows three very thin parallel planes of charge with equal separation 8 cm between them. The charge density of the middle plane is +4 nC/m2 (nC = "nano Coulomb") and that of the two outer planes is -2nC/m2. Use Gauss's law to solve the following questions. We choose positive electric field along the y-direction.
    What is the Electric Field at point C?

    2. Relevant equations
    E=ρD/ε Electric Field at position D


    3. The attempt at a solution
    I've tried to Calculate the E at distance between The top Positive ρ and the point C and from the bottom ρ to point C. Should these two be equal?
    From top:
    (4e-9c/m^2 * 0.004m) / ε to give me field to point C

    From bottom:
    (2e-9c/m^2 * 0.004m) / ε to give field to point C

    I know the field results in a - I've tried to add them to get the answer and subtract.
    What am I to do from this point?
    Am I using the wrong equation?


    Thanks!
     

    Attached Files:

  2. jcsd
  3. Feb 13, 2013 #2

    TSny

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    Homework Helper
    Gold Member

    The question asks you to use Gauss' law to find the answer. Since you want the field at point C, you should try to construct a Gaussian surface that goes through C. Choose the shape of the Gaussian surface so that you can take advantage of any symmetry in the problem.
     
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