An isolated capacitor has a dielectric slab k between its two plates. The capacitor is charged by a battery. After the capacitor is charged, the battery is removed. The dielectric slab is then removed. Finally, the capacitor reaches equilibrium. Initially the parallel-plate capacitor has a capacitance of 2.19nF is charged to an initial potential difference of 94 V. The dielectric material has a dielectric constant k = 7.54. What is the magnitude of the work required when the dielectric slab is then removed? I used: W= Ui - Uf U= 0.5CV^2 Uf= (0.5)C(k*Vi)^2 Ui = (0.5)C(Vi)^2 Vi=initial potential difference. I have tried to double check the math, so I guess I messed up with the formulas. Where did I go wrong?