Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Capacitor with two dielectrics.

  1. Jun 18, 2011 #1
    1. The problem statement, all variables and given/known data
    A parallel-plate capacitor contains two dielectrics of different electric permitivities and conductivities 1 and 2, respectively (they are separated by a line with the horizontal). A voltage V is applied to the terminals, find:
    The free and polarization charge densities.
    The resistance and capacity, in terms of the given parameters.

    3. The attempt at a solution
    Not sure how to answer the first question, I think they should be zero but I'm not sure why. I can see why the free charge density is zero in a dielectric (no free motion of electrons) but not polarization density (when a voltage is applied dielectric will become polarized).

    For resistance I'd just use ohm's law and rewrite I as the flux integral JdS, and rewrite J in terms of the conductivity and electric field, but should I add the two conductivities?

    Same goes for the capacity, I could just use the expression for a parallel plate capacitor, but I'm not sure if I'd need to add both permitivities or do something else.
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted