Question

A parallel-plate capacitor is connected to a power supply that
maintains a fixed potential difference between the plates.
a) If a sheet of dielectric is then slid between the plates, what happens to (i)
the electric field between the plates, (ii) the magnitude of charge on each
plate, and (iii) the energy stored in the capacitor?
b) Now suppose that before the dielectric is inserted, the charged capacitor is
disconnected from the power supply. In this case what happens to the
electric field, the magnitude of charge, and the energy stored?
Explain any difference between the2cases