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Homework Help: Dielectric and force between charges

  1. May 9, 2008 #1
    The problem statement, all variables and given/known data

    suppose I have a charge q at (x=-d) and a charge q at (x=+d).
    the force between them is q^2/(4*pi*(eps_0)*4*d^2).

    now, I insert a dielectric (K) between (-d/2<x<d/2), what would be the force between the charges now?

    The attempt at a solution

    it seems like it would be the same but it sounds strange...
    If I use the D field, it is not effected by the dielectrics, and thus I can see that the electrical field E is the same as before (D/eps_0) and thus the force is the same...

    could it be?????
  2. jcsd
  3. May 9, 2008 #2

    someone?? please???
    I really need help with this...
  4. May 9, 2008 #3


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    F=qE and E=D/(K*epsilonzero)
  5. May 10, 2008 #4
    that's just it, i don't think this is it.
    notice that the two charge are in the matter eps_0.

    * the other dielectric is only found at (-d/2 < x < d/2 ).
    * the two charges are in (x = -d) and (x = +d).

    so it seems like the force will be F=qE and E=d/eps_0.
    which is exactly like if there was no dielectric between them, and it seems pretty weird to me...
  6. May 10, 2008 #5


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    Science Advisor

    What happens at the dielectric surface/boundary?
    Reilly Atkinson
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