889. In the simplest terms, how does a basic electrical circuit work? — CC, Port St. Joe, FL
An electric circuit is racetrack for electric charges. It must be a complete loop—a "circuit"—so that the charges don't pile up somewhere along the track. The simplest circuit has a source of energy for the electric charges (e.g., a battery) and a device that takes energy away from the electric charges (e.g., a light bulb). When the charges are in motion through the circuit, they are an electric current. By convention, current points in the direction of positive charge flow, so you can imagine a stream of positive charges circling this circuit over and over again, with current pointing always in the direction that those positive charges are moving. As the current passes through the battery, entering it at the battery's negative terminal and leaving it at its positive terminal, the charges pick up energy. The battery is converting some of its stored chemical potential energy into electric energy and giving that energy steadily to the current flowing through it. The battery is "pumping" the charges from its negative terminal to its positive terminal. The current continues around the circuit and then passes through the light bulb. In the light bulb, the charges give up most of their energies to the filament and the filament becomes white hot. The current continues out of the bulb and returns to the negative terminal of the battery to pick up more energy. This simple circuit is present in a flashlight. The same charges complete this circuit millions of times each second, shuttling energy from the battery to the bulb.