A direct current (DC) cannot pass through a parallel plate capacitor because the dielectric between the plates is non-conducting. In a parallel plate capacitor, two conductive plates are separated by a dielectric material (usually an insulator). When a voltage (potential difference) is applied across the plates, it creates an electric field between them, which stores electrical energy in the form of electric potential. The dielectric material between the plates is a non-conducting material, which means it does not allow the flow of electric current. Therefore, in a DC circuit, where current is the flow of charge over time, current cannot flow through the dielectric. Instead, the dielectric serves to store energy in the electric field between the plates without allowing the passage of charge.