Question

Initially, the space between the plates of the capacitor is filled with air, and the field strength in the gap is equal to E0.

Answer 1

The capacitance of a set of charged parallel plates is increased by the insertion of a dielectric material. The capacitance is inversely proportional to the electric field between the plates, and the presence of the dielectric reduces the effective electric field.

                                   An insulating material which has the effect of increasing the capacitance of a vacuum-filled parallel plate capacitor, when it is inserted between its plates, is called a dielectric material, and the factor by which the capacitance is increased is called the dielectric constant of that material