Question

How does the stored energy change when a full dielectric is inserted into an isolated capacitor with constant charge?

Options

• \[U=\frac{K}{U_0}\]

• \[U=\frac{U_0}{K}\]

• \[U=U_0+K\]

• \[U=KU_0\]

Answer 1

For constant charge, stored energy is \[U=Q^2/(2C)\]. The capacitance increases by a factor of \[K\], so the stored energy decreases to \[U_0/K\].