Question 25.39: In Fig. 25-45,C1 = 10.0 μF, C2= 20.0 μF, and C3= 25.0μF. If ......

(a) They each store the same charge, so the maximum voltage is across the smallest capacitor. With 100 V across 10 μF, then the voltage across the 20 μF capacitor is 50 V and the voltage across the 25 μF capacitor is 40 V. Therefore, the voltage across the arrangement is 190 V.

(b) Using Eq. 25-21 or Eq. 25-22, we sum the energies on the capacitors and obtain U$_{total}$ = 0.095 J.

$U=\frac{q^2}{2 C}$        (potential energy).      (25-21)

$U=\frac{1}{2} C V^2$              (potential energy).        (25-22)