- Capacitance of a parallel-plate capacitor is given by the following expression: DE A C = QV d where, A is the area of plates, d is the distance between the plates, Eo is the permittivity of free-space or vacuum (8.854 x 1012 C'N'm), D is the dielectric constant of the medium (= 1 for free-space), Q developed on the metal plates on the application of potential difference V. Two parallel-plate capacitors are constructed by sandwiching following different insulating materials between square plates made of silver (side length = 1 cm) L 100 micrometres thick mica (dielectric constant = 5) i. 1 mm thick piece of glass (dielectric constant = 10) Which case will store a higher amount of charge?