An understanding of the relative amount of capacitance to be expected in a cable is helpful in specifying cable and designing terminal equipment for the cable to be used. Although capacitance in a cable may have negligible effect on DC or 60 cycle AC cable circuits used for power or control, it does affect higher frequency AC voltages. The more electrons that are concentrated on a surface, the larger the electric charge on that surface. Positively charged surfaces may be regarded as having a deficiency of electrons.
Charge is measured in coulombs.
One coulomb consists of many trillions of electrons. Since they repel each other, a collection of electrons will distribute over a surface. Since electrons in motion constitute an electric current current flows off one surface through the battery onto the other, untii the repulsion of charges being forced onto the surfaces equals the forcing voltage. When the battery is removed, a voltage equal to that of the battery exists between the surfaces due to the stored charge. If the voltage source is AC, the charge exchange occurs each half cycle.