An electric circuit is a path in which electrons from a voltage or current source flow.
The point where those electrons enter an electrical circuit is called the “source” of electrons. The point where the electrons leave an electrical circuit is called the “return” or “earth ground”. The exit point is called the “return” because electrons always end up at the source when they complete the path of an electrical circuit.
The part of an electrical circuit that is between the electrons’ starting point and the point where they return to the source is called an electrical circuit’s “load”. A load of an electrical circuit may be as simple as those that power home appliances like refrigerators, televisions, or lamps or more complicated, such as the load on the output of a hydroelectric power generating station.
Circuits use two forms of electrical power: alternating current (AC) and direct current (DC). AC often powers large appliances and motors and is generated by power stations. DC powers battery operated vehicles and other machines and electronics. Converters can change AC to DC and vice versa. High-voltage direct current transmission uses big converters.