Calculating Charge on Capacitors in Series

[slammer]

Homework Statement

A circuit composed of 2 capacitors of .40MF and .50MF are connected in series to a 9V battery. Calculate the charge on each

I just have a general question. I know that capacitors in series have the same charge.
I found Q to be 2MC and I was wondering if 1.8MC is the charge on both caps or is it .9MC charge on both caps.

 

[LowlyPion]

Homework Statement

A circuit composed of 2 capacitors of .40MF and .50MF are connected in series to a 9V battery. Calculate the charge on each

I just have a general question. I know that capacitors in parallel have the same charge.
I found Q to be 1.8MC and I was wondering if 1.8MC is the charge on both caps or is it .9MC charge on both caps.

Capacitors in parallel have the same voltage but not necessarily the same charge unless the capacitances are the same.

Q = v * C

As for your question about the 1.8 mC - that is what is across the "equivalent" capacitor.

If you were to figure the voltages of the 2 capacitors and know they are supposed to add to 9 v, you will be able to answer your own question about how the charges are distributed.

 

[slammer]

Oops sorry my bad i mean capacitors in series have same charge. But I can't solve for V w/o finding out the capacitance on each capacitor. So what I am trying to say is does the both of the capacitors get 1.8mC of charge or do they each get .9mC?

 

[LowlyPion]

Oops sorry my bad i mean capacitors in series have same charge. But I can't solve for V w/o finding out the capacitance on each capacitor. So what I am trying to say is does the both of the capacitors get 1.8mC of charge or do they each get .9mC?

What voltage do you get across each capacitor for both of those possibilities?

Which possibility adds up to 9 v adding the voltages of both capacitors? Because that's the one that's your answer.

Btw, where did the 1.8 mC come from? Didn't you calculate the equivalent capacitance and multiply by the voltage?

 

[slammer]

What voltage do you get across each capacitor for both of those possibilities?

Which possibility adds up to 9 v adding the voltages of both capacitors? Because that's the one that's your answer.

Btw, where did the 1.8 mC come from? Didn't you calculate the equivalent capacitance and multiply by the voltage?

round errors and I figured it out. 1.8mC gets dumped on both of the caps.

 

[LowlyPion]

round errors and I figured it out. 1.8mC gets dumped on both of the caps.

Well if you had used 2 mC it would have maybe been a little more obvious?

Cheers.