The direct current circuit is the closed path in which direct current flows and is time independent. Since current flows in just one direction, it is commonly used in low voltage applications. The resistor is the most important component of the DC circuit. The historical significance of any circuit voltage or current has little effect on the circuit's current or voltage. This means that no time integrals or derivatives are used in the equation scheme that describes a DC circuit. Even if the circuit is defined as DC driven, it is common in electronics to refer to a circuit operated by a DC voltage source such as a battery or the output of a DC power supply as a DC circuit