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Nonconductive wall with charge density and finding electric field

  1. Feb 9, 2009 #1
    1. The problem statement, all variables and given/known data
    A nonconducting wall carries a uniform
    charge density of 13.62 μC/cm2.
    What is the electric field 5.7 cm in front of
    the wall? Answer in units of N/C.



    2. Relevant equations
    Gauss's law...?


    3. The attempt at a solution
    Honestly, this bugger's got me scratching my head since our prof never even mentioned it in lecture, and I'm trying to get the homework done a week ahead of time. I've looked around for the relation of electric field to charge density...and it's not been pretty. I tried E=Q/e where little e is our freespace constant, but that's wrong, so I'm not seeing this right.

    And I've searched everywhere on the web and not one god damned how-to for this type of problem. Anybody want to be merciful?
     
  2. jcsd
  3. Feb 9, 2009 #2

    gabbagabbahey

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    Are you told the dimensions of the wall? Or are you supposed to assume that it is "very large"?

    If you are 5.7 cm from a "very large wall", it essentially looks like an infinite plane doesn't it?....Surely you've calculated the field due to a uniformly charged infinite plane in your lectures?:wink:
     
  4. Feb 9, 2009 #3
    You'd be amazed just how bad my prof is. We haven't. And the problem is the problem word for word. Just told it has a uniform charge density, and to find the electric field.

    I did try E=σ/2ε. Shot down my answer twice with it. :/
     
  5. Feb 9, 2009 #4

    gabbagabbahey

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    Did you make sure to convert your answer to units of N/C? What was your answer?
     
  6. Feb 9, 2009 #5
    769491 was the latest one. I take care of the coulomb and meter conversions when I punch through the calculations, so I'm not sure what exactly is up with this problem. Since the answer is rather large it might just be anal about significant figures of some sort since it doesn't define any freespace constants, as they usually do. Blah...
     
  7. Feb 9, 2009 #6

    gabbagabbahey

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    You seem to be missing about 4 zeroes from the end of that!
     
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