A battery or generator produces voltage -- the force that drives current through the circuit. Take the simple case of an electric light. Two wires connect to the light. For electrons to do their job in producing light, there must be a complete circuit so they can flow through the light bulb and then back out.our blood vessels, arteries, veins and capillaries are like the wires in a circuit. The blood vessels carry the flow of blood through your body. The wires in a circuit carry the electric current to various parts of an electrical or electronic system.