Capacitance in Parallel and in Series

[islandboy401]

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: C_eq = C₁ + C₂ + C₃ +...

For series capacitors:

The Attempt at a Solution

My answer is 4.74 nF though my answer key says 3.16 nF. Am I doing something wrong?

 

[unknown_2]

in series : $$\frac{1}{C_{eq}}$$ = $$\frac{1}{C_{1}}$$ + $$\frac{1}{C_{2}}$$ + $$\frac{1}{C_{3}}$$... etc

in parallel $${C_{eq}$$ = $${C_{1}$$ + $${C_{2}$$ + $${C_{3}$$ ... etc

basically the opposite to resistance

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

so it should be $$\frac{1}{C_{eq}}$$ = $$\frac{1}{10 + 5}$$ + $$\frac{1}{4}$$

so $$C_{eq}$$ = 3.16nF

hopefully that helps

 

[islandboy401]

Thanks...I understand what I did wrong.