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Gauss Law in a plane sheet, and thick sheet (Infinite)

  1. Apr 3, 2015 #1
    We have learnt the below formula for a plane sheet of charge with thickness.

    E=σ/ϵ

    and the one below for with no thickness (negligible)

    E=σ/2ϵ

    The problem, I am facing is digesting the derived equations. It is one thing for sure that these formulas must be right. But then the fact that E is proportional to the square of the distance between the test charge (Or any other charge, taken from columbs law.) is disobeyed by it (Atleast that's what I think.) I have seen alternate derivations with the same expression. Why is this not obeyed, or is it obeyed over here.

    Thank you.
     
  2. jcsd
  3. Apr 4, 2015 #2
    The contribution from each individual charge does obey the inverse square law, but the geometry of the situation leads to the result.
    This might help
    http://mlg.eng.cam.ac.uk/mchutchon/chargedPlanes.pdf
    Notice that the sin θ term increases with the distance from the plate and this counteracts the inverse square relationship.
     
  4. Apr 4, 2015 #3
    Thanks a tonne :D
     
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