Electric circuits or networks are formed by interconnecting various devices, sources, and components. Although the effects of each element (such as heating effects, electric-?eld effects, or magnetic-?eld effects) are distributed throughout space, one often lumps them together as lumped elements. The passive components are the resistance R representing the heating effect, the capacitance C representing the electric-?eld effect, and the inductance L representing the magnetic-?eld effect. Their characteristics will be presented in this section. The capacitor models the relation between voltage and current due to changes in the accumulation of electric charge, and the inductor models the relation due to changes in magnetic ?ux linkages, as will be seen later. While these phenomena are generally distributed throughout an electric circuit, under certain conditions they can be considered to be concentrated at certain points and can therefore be represented by lumped parameters.