Capacitance Problem: Getting Charge on Each Capacitor

[Lancelot59]

I'm given that a $$2.0\mu F$$ capacitor is charged with 300V and $$6.0\mu F$$ capacitor is charged at 150V. They are then disconnected from the batteries and connected to each other.

I correctly got the net charge between their plates as $$3.0*10^{-4}C$$, however I can't get the charge on each capacitor. I tried getting the equivalent series capacitance, dividing by the net charge to get the voltage, and then using that voltage to get the charge. It didn't work. How can I go about getting the charge on each capacitor?

 

[gneill]

You should state *how* they are connected to each other. Positive plate to positive plate? Positive to negative? Simply in series with one lead each free? Details matter.

Now, presumably since you state that the net charge after connection is 3.0 x 10^-4 C, they've been connected in parallel, negative plate to positive. What's the net capacitance for two capacitors connected in parallel? Given the charge as you've stated, what's the voltage on the net capacitance?

 

[Lancelot59]

Actually it's negative to positive, would that not be treated as a series circuit?

 

[gneill]

Did you not read the rest of my reply?

 

[Lancelot59]

I did. It just sounds to me like positive to negative would be a series connection, not parallel. Why do you treat it as parallel?

 

[gneill]

The polarity of the plates has nothing to do with determining series or parallel. What matters is whether or not both leads of both capacitors are connected to each other with nothing else in between.

 

[Lancelot59]

Drawing that on paper still comes out as series to me. Eh, Ill just take your word for it.