Publisher Summary This chapter describes the properties of capacitors and the concept of capacitance. Electrostatic is the branch of electricity that is concerned with the study of electrical charges at rest. An electrostatic field accompanies a static charge and this is utilized in the capacitor. Charged bodies attract or repel each other depending on the nature of the charge. The rule is—like charges repel, unlike charges attract. A capacitor is a device capable of storing electrical energy. The difference in charge between the plates results in a potential difference (p.d.) existing between them, the flow of electrons dying away and ceasing when the p.d. between the plates equals the supply voltage. The plates are then said to be charged and there exists an electric field between them. A dielectric is an insulating medium separating charged surfaces. Every system of electrical conductors possesses capacitance. For a parallel plate capacitor, capacitance is proportional to area, inversely proportional to the plate spacing, and depends on the nature of the dielectric and the number of plates.