Electric Current Most electrical devices are not electrostatic devices.
Most electrical devices require the flow of a current.
A current requires moving charges. The current density is a vector . It represents the amount of net charge that crosses a unit area perpendicular to the flow per second. If just as many negative as positive charges move across a unit area in the same direction per second, then the current density is zero. In ordinary conductors the positive charges have zero average velocity and only the negative charges are moving.