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Capacitance in Parallel and in Series

  • #1

Homework Statement



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.


Homework Equations



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

For series capacitors:
Series%20Capacitance.JPG


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?

Homework Statement





Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
29
0
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
 
  • #3
Thanks...I understand what I did wrong.
 

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