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!

Capacitor in AC circuit

  1. Apr 22, 2008 #1
    When a capacitor is connected in a circuit with an ac supply, a current flows in the circuit. fine. The problem is, does a pd develops across that capacitor, and does it store energy. As in does it "Charge" up?
  2. jcsd
  3. Apr 22, 2008 #2
    oh sorry, this thread shouldnt have been here.
    But still, anyone?
  4. Apr 22, 2008 #3
    Yes. No. Yes. No. Yes. No....:smile:
  5. Apr 22, 2008 #4
    ok now...comeon....:P

    say it clearly, im too dumb to understand your joke....

    Yes or no?
  6. Apr 22, 2008 #5
    Yes, there will be an ac Voltage across the capacitor. Depending on the quality of the capacitor, the Voltage will lag the current by up to 90 degrees.
  7. Apr 22, 2008 #6
    so will it store energy?

    since w=1/2 cv^2
  8. Apr 22, 2008 #7


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    A capacitor does store energy, but it is stored in the electric field between the plates. As the charge builds up on the two plates, a potential difference, and hence an electric field, is generated between the plates. To put more charge on the plates an emf must do work against this electric field and it is this work which is 'stored' as energy in the field.

    Do you follow?
  9. Apr 22, 2008 #8
    ok so what about AC current which changes direction 50 times every second?
    The direction of electric field has to change also.....
    So will it constantly cancel each other's effect or what?
  10. Apr 22, 2008 #9


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Here's a nice reference on http://www.physclips.unsw.edu.au/jw/AC.html#capacitors" [Broken].
    Last edited by a moderator: May 3, 2017
  11. Apr 22, 2008 #10
    That was helpful.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook