Calculating Capacitance in a Mixed Circuit?

[brinstar]

Homework Statement

Please calculate the equivalent capacitance if C1 = 10.3 microfarads, C2 = 41.1 microfarads, and C3 = 95.5 microfarads in the diagram.

Homework Equations

1 / Ctotal for Parallel = (1/C1) + (1/C2) + ...
Ctotal for Series = C1 + C2 + ...

The Attempt at a Solution

So I tried to split it up. The total for the parallel part was 28.73389458 microfarads. Then the series was 10.3 microfarads, so when I add it up, I get 39.03389458 microfarads. Is this right?

 

[cnh1995]

1 / Ctotal for Parallel = (1/C1) + (1/C2) + ...
Ctotal for Series = C1 + C2 + ...

Are you sure?

 

[brinstar]

Are you sure?

Oops, sorry! It's the opposite, my bad >.<

Now I'm getting 146.9 microfarads?

 

[cnh1995]

Are you sure you should add the 10.3 microfarad directly to the parallel combination?

 

[gneill]

A quick reality check is to realize that any time you have capacitors in series the result must be less than the smallest in the string. In your figure capacitor C1 is definitely in series with whatever net capacitance follows it...

 

[brinstar]

Are you sure you should add the 10.3 microfarad directly to the parallel combination?

Well, being that I have absolutely no idea how to face this situation, I'm as sure as can be with a wild guess :/ I'm guessing I did it wrong, though, right?

So should I be adding its inverse?

 

[cnh1995]

Well, being that I have absolutely no idea how to face this situation, I'm as sure as can be with a wild guess :/ I'm guessing I did it wrong, though, right?

So should I be adding its inverse?

Yes. Series capacitors add like parallel resistors.

 

[brinstar]

Yes. Series capacitors add like parallel resistors.

Ah okay, I think I got it: 9.55 microfarads

Thank you!

 

[cnh1995]

Ah okay, I think I got it: 9.55 microfarads

Good! In such addition, the result is always less than the least of the component values, as gneill mentioned in #5.

 

[brinstar]

Good! In such addition, the result is always less than the least of the component values, as gneill mentioned in #5.

thank you for the help!