1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    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 required to charge up a capacitor

  1. Jun 12, 2012 #1
    The energy required to charge a capacitor is:

    W = ½εrCV2

    From this we see that a capacitor with a linear dielectric in between its plates requires a bigger energy to charge up to a given potential. My question is: Should this be intuitive?
    My teacher said that it is because the parts of the electric field is cancelled off by the bound charges. I guess I can understand that since you then have to pull in more charge overall. However - wont these charges being pulled in also experience a weaker repulsion due to the cancelled off charges?
  2. jcsd
  3. Jun 12, 2012 #2


    User Avatar

    Staff: Mentor

    Welcome to the PF.

    Your equation does not look correct. See for example this thread:


    If you want to include non-linear dielectric effects, then it seems like you would write the capacitance as a function of voltage, like:

    [tex]W = \frac{1}{2}C(V)V^2[/tex]

    And use an integral to calculate how much energe is stored in charging up the cap...
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook