Capacitors in circuit

This chapter discusses applications of capacitors in circuits. In parallel connections, the charges on each capacitor will depend upon the individual capacitances, while for series connections, the charge on each capacitor remains same. When an electric field is established in a dielectric, there is a distortion of the electron orbits around the atoms making up the dielectric material. This effect produces a mechanical stress in the dielectric, which in turn produces heat. Because the production of heat represents a dissipation of power, practical dielectrics always introduce a power loss, generally very small but particularly important when the capacitors are used in high frequency circuits where there is a continual and rapid change of plate polarities. If the potential difference between the plates of a capacitor is increased beyond a certain amount, a point is reached where the dielectric insulation is unable to withstand the electric stress setup across it, and there is a spark discharge that penetrates the material and destroys its insulating properties in the region of the breakdown. The potential gradient necessary to cause such a breakdown is a measure of the ability of a material to resist breakdown, which is usually expressed in volts or kilovolts per millimeter. The mechanical problems of capacitor design depend largely upon three factors: (1) the capacity required, (2) the maximum working voltage at which it can be used, and (3) whether it is to be employed at direct current at low frequencies or at high frequencies.