Question

An isolated capacitor of unknown capacitance has been charged to a potential difference of 100 V. When the charged capacitor is then connected in parallel to an un-
charged 10.0 μF capacitor, the potential difference across the combination is 30.0 V.
Calculate the unknown capacitance.
10.0µF=10*10^-6F. C=Q/V => c=(10*10^-6)/70= unknown capactitance?
Im guessing this is it?

Answer 1

C = Q / 100...100 C = Q

capacitors add in parallel

the charge is the same (redistributed)

C + 10 = 100 C / 30

solve for C