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Free and bound charge at dielectric-conductor interface

  1. Oct 23, 2008 #1
    Say I have a capacitor filled with a linear dielectric in a purely electrostatic setup. Then there will exist a uniform electric field inside the capacitor, and the field inside the electrodes is of course zero. The dielectric will polarize, and I should get bound charge at the dielectric-conductor interface. It seems to me that you would also get some induced free charge from the conductor as well at this interface.

    What kind of coulomb forces would I get in this situation, if what I described is in fact correct?

    To generalize my question, what in general happens at a conductor-dielectric interface? How does the induce charge behave? Is there only surface polarization charge from the dielectric, or does induced free charge come into play from the conductor?

  2. jcsd
  3. Oct 25, 2008 #2


    Staff: Mentor

    Actually, you have it exactly backwards. There is an applied charge on the surface of the conductor that causes the E-field between the plates. The dielectric material polarizes in response to this externally applied E-field. For all practical purposes the dielectric is uncharged, including on its surface. Being polarized is not the same as being charged.
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