Potential difference across capacitors, can someone check this?

[JFonseka]

Homework Statement

What is the potential difference across C2 when C1 = 5.0 µF, C2 = 15 µF, C3 = 30 µF, and V0 = 24 V?
http://img503.imageshack.us/img503/9994/capacitanceqb1.jpg

Homework Equations

C = Q/V

The Attempt at a Solution

I calculated total capacitance of C1 and C3 in parallel, that is 3.5 x 10^-5 Farads.

So the charge going across is Q = CV = 3.5x10^-5 x 24 = 8.4 x 10^-4 C

Therefore the voltage going across the other capacitor is V = Q/C, which 8.4x10^-4/15x10^-6 = 56V

Which looks really wrong.

Help?

Thanks in advance.

 

[JFonseka]

Wait I redid it. I first calculated the total capacitance which turned out to be 1.5x10^-5 Farads.

Got the total charge by Q = CV, 1.5x10^-5 x 24 = 3.6x10^-4 C

3.6x10^-4/15x10^-6 = 24 V

So is that right?

 

[ogb p]

I would approach this problem by first double-checking my calculations to ensure that I have not made any errors. I would also consider the fact that the capacitors are connected in series, meaning that the charge on each capacitor is the same. Therefore, the potential difference across each capacitor can be calculated using the formula V = Q/C, where Q is the total charge and C is the individual capacitance.

In this case, the total capacitance is 50 µF (5+15+30), and the total charge is 8.4 x 10^-4 C. Therefore, the potential difference across C2 would be V = 8.4x10^-4/15x10^-6 = 56V, which is the same as your previous calculation. This may seem counterintuitive since C2 has a larger capacitance, but it is due to the fact that the larger capacitance is offset by the smaller charge on C2 compared to C1 and C3.

I would also suggest checking the direction of the potential difference across each capacitor to ensure it aligns with the given diagram. If the potential difference is in the opposite direction, it would result in a negative value.

In summary, it is important to double-check calculations and consider the circuit configuration when determining the potential difference across capacitors.