18.71 A 13.5 micro F capacitor is connected to a power supply that keeps a constant potential difference of 26.0 V across the plates. A piece of material having a dielectric constant of 3.75 is placed between the plates, completely filling the space between them. A. How much energy is stored in the capacitor before the dielectric is inserted? in J B. How much energy is stored in the capacitor after the dielectric is inserted? in J C. By how much did the energy change during the insertion? in J