Two identical air-filled parallel-plate capacitors C1 and C2,
each with capacitance C, are connected in series to a battery that
has voltage V. While the two capacitors remain connected to the
battery, a dielectric with dielectric constant K > 1 is inserted
between the plates of one of the capacitors, completely filling the
space between them. Let Up be the total energy stored in the two
capacitors without the dielectric and U be the total energy stored
after the dielectric is inserted. In terms of K,
what is the ratio U/Uo? Does the total stored energy increase,
decrease, or stay the same after the dielectric is
inserted?