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Homework Help: Help with Dielectrics

  1. Jan 4, 2009 #1
    Hi. I have a problem in trying to find the field [tex] \vec E [/tex] in the following situation:
    I have an infinite charged plane, with charge density [tex] \sigma [/tex], and two dielectrics, like in picture:
    http://img53.imageshack.us/img53/2301/testrb0.jpg [Broken]
    Now, if i think of [tex] \vec D [/tex] being orthogonal to the charged plane, using Gauss law i get [tex] \vec D = \frac{\sigma}{2} \vec k [/tex], then i get the fields [tex] \vec E [/tex]in the dielectrics: [tex] \vec E_1 = \frac{\sigma}{2\varepsilon_0 k_1} \vec k [/tex] and [tex] \vec E_2 = \frac{\sigma}{2\varepsilon_0 k_2} \vec k [/tex].. but, because of [tex] \oint \vec E \cdot d\vec x = 0 [/tex], I obtain [tex] E_{t_1} = E_{t_2}[/tex] , where [tex] E_{t_i}[/tex] is the tangential (to the contact surface of dielectrics) component of [tex] \vec E [/tex] in dielectric [tex] i [/tex]. But [tex] E_{t_1} = \|\vec E_1}\| \ne \|\vec E_2\| = E_{t_2}[/tex].

    What is wrong?
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Jan 4, 2009 #2


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    Re: Dielectrics

    The basic equation is E1=E2. Then find D1 and D2. There will be a sigma1 and silgma2.
  4. Jan 4, 2009 #3
    Re: Dielectrics

    In the problem [tex]\sigma[/tex] is fixed :shy:
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