Can vacuum be used as dielectric between metal plates of a capacitor?

Yes, a vacuum can be used as a dielectric between the metal plates of a capacitor. In fact, a vacuum has a dielectric constant of 1, which means it is an ideal insulator that does not allow current to flow between the plates while enabling the formation of an electric field. This results in a capacitor with a high breakdown voltage and can effectively store electrical energy. However, practical capacitors usually use other materials as dielectrics to achieve higher capacitance values.