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Homework Help: Problem On capacitor

  1. Jun 29, 2004 #1
    i am new to this forum from india and preparing for IIT
    well i have question
    "If a dielectric is placed between two plates of parallel plate capacitor which is isolated and charged the force between plates decrease or remain same . well i found answer in my book that it remains same but i dont know why?
    i think it should be reduced becuase induced charges appear on the edges of dieelectric and due to these charges two electric field nullify some of the effect?"
    Please help
  2. jcsd
  3. Jun 29, 2004 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Welcome to PF!

    Consider first the capacitor without a dielectric. The charge on one plate creates an electric field which exerts a force on the other plate. That field is proportional to the surface charge density, and is independent of distance. When the dielectric is introduced, induced surface charges do appear on each side of the dielectric, but they cancel. (They effect the field within the dielectric, but not outside it.)
  4. Jun 30, 2004 #3

    THANX for help
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