Find Final Voltage of Parallel Capacitors

[pelzerni]

Homework Statement

Two capacitors of 34.0 μF and 125 μF are separately charged to 126 μC and 250 μC, respectively. They are then attached in parallel so that the + plate of one goes to the - plate of the other, and vice versa. Determine the final voltage across the two plates.

Homework Equations

C=Q/Vc

The Attempt at a Solution

I calculated the change in voltage by adding Q1 and Q2 and then dividing by the sum of C1 and C2. (126+250)/(34+125)=2.36 V. How do I find the initial voltage so that I can get the final voltage?

 

[lewando]

Note how the 2 caps are attached to each other. "Initial voltage" does not seem like a relevant concept.

 

[tomcue]

To find the initial voltage, you can use the formula V=Q/C, where V is the voltage, Q is the charge, and C is the capacitance. In this case, you can use the values of Q1 and Q2 and the respective capacitance values of C1 and C2 to find the initial voltage for each capacitor. Once you have the initial voltage for each capacitor, you can then use the formula V=Q/C to find the final voltage across the two plates. The final voltage will be the same for both capacitors since they are in parallel.