What distinguishes active power from reactive power in an electrical system?

The distinction between active power and reactive power is fundamental in understanding how electrical systems operate. Active power, measured in watts, represents the portion of electrical power that is used to perform useful work, such as lighting a bulb, running a motor, or heating. This type of power is what is consumed by electrical devices to produce work and is essential for the functionality of these devices in a power system.

On the other hand, reactive power, measured in volt-amperes reactive (VAR), does not perform useful work in the same way but is necessary for creating electric and magnetic fields in inductive and capacitive components, such as transformers and motors. Essentially, reactive power supports the operation of these components without contributing to net work output. This ability to maintain voltage levels and support the transmission of active power is crucial for the stability and efficiency of the electrical grid.

Therefore, the correct understanding is that active power performs useful work while reactive power supports the electric fields that are necessary for devices to function properly in an alternating current (AC) system. This understanding is vital for ensuring that electrical systems operate efficiently and effectively.