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!

Capacitors in circuits

  1. Mar 27, 2014 #1
    If a capacitor is fully charged in a circuit, am I correct in saying that you can ignore that section of the circuit because no current goes through/leaves it?
     
  2. jcsd
  3. Mar 27, 2014 #2

    BiGyElLoWhAt

    User Avatar
    Gold Member

    In DC, yea, pretty much, but not in AC. In AC circuits they act as high pass filters.
     
  4. Mar 27, 2014 #3

    BiGyElLoWhAt

    User Avatar
    Gold Member

    I would still math it out, just because some circuits can do wierd things, but most caps can handle upwards of a couple hundred volts, and if it's "fully charged" you're either saying: 1 it's in equilibrium with the voltage supply, or 2 it's at a higher voltage then your voltage supply, so current flows backwards, unless you have a huge supply.
     
  5. Mar 27, 2014 #4
    I am only learning DC right now, so do I still need to worry about that?

    Also, if you have a capacitor that is not fully charged, how would you analyze the circuit then?
     
  6. Mar 27, 2014 #5
    IN the case of DC - and in a steady state - nothing changing, once the cap is charged, it "looks" like an open circuit. As soon as anything changes in time, the capacitor needs to be considered.
    So when you say not fully charged - what do you mean, charged to it's maximum voltage - or you change something in the circuit like close a switch? For example - at Time 0 the cap is at 2 V and then something changes and the capacitor may charge to 6V.... this is still a DC case, but the Capacitor needs to included in your analysis.
     
  7. Mar 27, 2014 #6

    BiGyElLoWhAt

    User Avatar
    Gold Member

    I'm pretty sure you'll want to use q=VC for it. Charge stored in the capacitor = voltage across the capacitor time its capacitance. If its not, sorry, I haven't analyzed DC circuited in forever. The only other equation coming to mind is the impedence, but that requires a frequency. Z=1/iwc in AC you use both, q for time dependent analysis, and z for complex analysis. Hope this helps, if not Google is your best friend, I'd look but I'm on my Droid now
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Capacitors in circuits
Loading...