1. Not finding help here? Sign up for a free 30min 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 in Parallel and in Series

  1. Mar 23, 2009 #1
    1. The problem statement, all variables and given/known data

    In the FIGURE (shown below in "attempt at solution" section), find the equivalent capacitance of the combination. Assume that C1=10 nF; C2 = 5 nF; and C3 = 4 nF.


    2. Relevant equations

    For parallel capacitors: Ceq = C1 + C2 + C3 +...

    For series capacitors:
    Series%20Capacitance.JPG

    3. The attempt at a solution

    number%209.jpg

    My answer is 4.74 nF though my answer key says 3.16 nF. Am I doing something wrong?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Mar 23, 2009 #2
    in series : [tex]\frac{1}{C_{eq}}[/tex] = [tex]\frac{1}{C_{1}}[/tex] + [tex]\frac{1}{C_{2}}[/tex] + [tex]\frac{1}{C_{3}}[/tex].... etc

    in parallel [tex]{C_{eq}[/tex] = [tex]{C_{1}[/tex] + [tex]{C_{2}[/tex] + [tex]{C_{3}[/tex] ... etc

    basically the opposite to resistance

    so from your diagram... (C1 // C2) + C3

    so it should be [tex]\frac{1}{C_{eq}}[/tex] = [tex]\frac{1}{10 + 5}[/tex] + [tex]\frac{1}{4}[/tex]

    so [tex]C_{eq}[/tex] = 3.16nF

    hopefully that helps
     
  4. Mar 23, 2009 #3
    Thanks...I understand what I did wrong.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook