Active power, measured in watts (W), is the actual power consumed by electrical devices to perform useful work. It represents the energy that is converted into mechanical work, heat, or light. In an electrical circuit, active power is the portion of power that contributes to the output, as opposed to reactive power, which does not perform any useful work. Active power is crucial for the efficient operation of appliances like light bulbs, motors, and heaters. Understanding active power helps in managing energy consumption and optimizing the performance of electrical systems, ensuring that devices operate effectively while minimizing waste.