The dielectric material used will determine when to apply the capacitor, which is responsible for storing energy and the amount of electrical charge it stores called capacitance. The dielectric material can be composed of various materials such as ceramics, teflon, mica, porcelain, cellulose, or even air. Dielectric is the insulating material that becomes conductive when subjected to certain electric field value. This change of state, from insulation to conductor, occurs when the electric field is greater than the dielectric strength of the material, that is, even the insulating materials can lead when dominated to determined value of electric charges.
Electrostatics is the branch of physics that studies electrical charges that are at rest, or in equilibrium, so when they are not in motion. When the capacitor is charging or discharging there is a variable value of electric current, but since there is a dielectric material between the plates of the capacitor, that energy goes from one plate to another and is stored. When the capacitor is fully charged (stationary) or fully discharged (open) there is no power flow because the charges are not in motion. To be electric current, the loads must be in motion.