Question

a parallel -plate capacitor has plate separation d. the space between the plates is empty. a battery supplying voltage v o is connected across the capacitor , resulting in electromagnetic energy u o stored in the capacitor . a dielectric of dielectric constant k is inserted so that it just fills the space between the plates .if the battery is still connected, what are the electric field e and the energy u stored in the dielectric in terms of vo and uo

Answer 1

the capacitance increases by a factor of k but since the battery is same the potential difference is constant the charge on the capacitor will change accordingly
so the final energy will be k*uo