current

Electric current is the phenomenon most often experienced in the form of electricity. Any time an object with a net electric charge is in motion, such as an electron in a wire or a positively charged ion jetting into the atmosphere from a solar flare, there is an electric current; the total current moving through some cross-sectional area in a given direction is simply the amount of positive charge moving through that cross-section. Current is sometimes confused with electric potential or voltage, but a voltage difference between two points (such as the two terminals of a battery) means only that current can potentially flow between them; how much does in fact flow depends on the resistance of the material between the two points. Electrical signals transmitted through a wire generally propagate at nearly the speed of light, but the current in the wire actually moves very slowly: pushing electrons into one end of the wire is rather like pushing a marble into one end of a tube filled with marbles—a marble (or electron) gets pushed out the other end almost instantly, even though the marbles (or electrons) inside move only incrementally.