Two capacitors are identical, except that one is empty and the other is filled with a dielectric (k = 3.9). Th

Two capacitors are identical, except that one is empty and the other is filled with a dielectric (k = 3.9). The empty capacitor is connected to a 15 -V battery. What must be the potential difference across the plates of the capacitor filled with a dielectric so that it stores the same amount of electrical energy as the empty capacitor?

V2 = __________ V

Energy stored in capacitor = 0.5 * C * V^2

C2 (with dielectric) = 3.9 * C1

So voltage across C2 for same energy is V2 = sqrt (15^2 / 3.9) = 15 / sqrt(3.9)

V2 = 7.60 V