Electric fields build up wherever there are differences in charge between two electrically charged parts. For example, between the two electrodes of a capacitor.
The lines of force of the electric field exert a force on conductive parts that are in the electric field (E field), which can change the position of the parts. The electric field strength (E) depends on the voltage difference of the applied voltage and the distance between the two electrodes; the field lines go from the positively to the negatively charged electrode. Accordingly, the electric field strength is expressed in volts/ meter(V/m).
There is a natural electric field that builds up between the earth's surface and the ionosphere. And there are undesirable electric fields, such as those emanating from high-voltage power lines, which can affect electrical signals, components, circuits, and equipment. A typical occurrence of this is power line hum, which radiates from the power supply onto the circuitry and superimposes a 50- Hz hum on the signal. For this reason, interfering electric fields are shielded by metallic grids, surfaces or housings. The permeability of matter to electric fields is the permittivity.