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!

Capacitance Question

  1. Oct 27, 2007 #1
    Hey gang,
    I am doing a Mastering physics question, and it's got me stumped. ><

    Q: You need a capacitance of 50.0 microF, but you don't happen to have a 50.0 microfarads capacitor. You do have a 80.0 microF capacitor.

    What additional capacitor is needed to get a capacitance of 50 microF?

    I was thinking it has something to do w/ C = Q / deltaV. But that would mean that I would need to have some sort of knowledge of Q. I then tried

    Ceq = (1/C1 +1/C2)^-1
    and solved for 1/C1 to get 49.9875 microF. But that doesn't seem logical (+ I got it wrong ><)

    Any suggestions / help? Greatly appreciated!
  2. jcsd
  3. Oct 27, 2007 #2


    User Avatar
    Gold Member

    Well you obviously solved for the unknown incorrectly. Why not try to solve the simpler equation (assuming series capacitors):

    [tex]C_{eq} = \frac{C1 \cdot C2}{C1+C2}[/tex]
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook