Capacitor how the plates are connected

[rasmusuperfan]

Homework Statement

Capacitor C1 is charged so that potential difference between its plates is 20V. Another capacitor C2=33 microF has potential difference of 4 V. After plates of the capacitor that carry the charge of the opposite sign were connected the potential difference became 2V, find C1.

Homework Equations

Q=C/V

The Attempt at a Solution

I know Q1=C1*20V and Q2=(33uF)*(4V), but don't have the slightest clue what happens when the plates are connected. Are they connected in series, or parallel, does that even matter? I know there is a conservation of charges, but would it be something like (Q1-Q2) = Ceq*V? Thanks for any help or guidance

 

[gneill]

They end up in parallel, and yes, there will be some charge cancellation.

 

[rasmusuperfan]

I am sorry, but I still don't see what to do. I feel like this is a simple problem, but I am lost. I don't want to seem like I am just asking for an answer, but I've been struggling with this for the past 2 hours and nothing is making sense. After they are connected it would be something like Q=(C1+C2)*V, but what is the charge? Would Q= Q1-Q2 or something like that?

 

[gneill]

Yes, Q1 - Q2, or Q2 - Q1, whichever yields a positive remainder -- it is stated that the final potential difference is 2V, a positive number.