Active power, measured in watts (W), is the portion of electrical power that performs useful work in a circuit. It represents the actual energy consumed by devices like light bulbs, motors, and heaters to produce heat, light, or mechanical motion. Active power is essential for the functioning of electrical appliances and is a key factor in energy consumption. In an electrical system, active power is distinct from reactive power, which does not perform useful work but is necessary for maintaining voltage levels. The relationship between active power and reactive power is crucial for understanding the overall efficiency of power systems, especially in industries and large facilities.