1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Energy of a parallel plate capacitor homework

  1. Nov 30, 2013 #1
    Hi all

    "A parallel plate capacitor in which plates of area A are separated by a distance d, has a capacitance C = [itex]\frac{Aε_{0}ε_{r}}{d}[/itex]
    It is charged to a pd V. Neglecting edge effects, derive an equation for the electric field E in the capacitor, and show that the energy stored per unit volume is w= 0.5[itex]ε_{r}ε_{0}E^{2}[/itex]"

    I believe that the electric field in a capacitor to be equal to [itex]\frac{\sigma}{\epsilon_{0}}[/itex]
    via Gauss Law, and using V = Ed you can then get V = [itex]\frac{\sigma d}{\epsilon_{0}}[/itex].

    I have then tried to use the various equations for work done = 0.5CV^2, 0.5QV etc to no avail.

    Any help much appreciated.

  2. jcsd
  3. Dec 1, 2013 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    That would be correct if the interplate material is air, but it's not.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted