A Direct Current circuit is a circuit that Electric Current flows through in one direction. DC is commonly found in many low-voltage applications, especially where these are powered by Battery. Most electronic circuits require a DC power supply. A Direct Electric Current flows only when the Electric Circuit is closed, but it stops completely when the circuit is open. A Switch is a device for making or breaking an Electric Circuit. While the Switch is closed, Figure 1(a), the circuit is closed and the Light Bulb turns On; while the Switch is opened, Figure 1(b), the circuit is open and the Light Bulb turns Off.