Define power factor in AC circuits.

In an AC circuit, power is delivered in two forms: real power (P) and reactive power (Q). Real power does useful work, such as powering appliances or generating heat, while reactive power is required for magnetic fields in inductive components (e.g., motors, transformers, coils) and capacitive elements in capacitors.

The apparent power (S) in an AC circuit is the vector sum of real power and reactive power:

S = √(P^2 + Q^2)

The power factor (PF) is then calculated as the ratio of real power to apparent power:

PF = P / S

The power factor ranges from 0 to 1, or 0% to 100%. A power factor of 1 (or 100%) means all the power supplied to the circuit is being used for useful work (no reactive power is present). A power factor less than 1 indicates that some of the power is being lost as reactive power, leading to inefficiencies in the system.

Efficient electrical systems strive to have a power factor as close to 1 as possible. Low power factors can lead to increased energy consumption, higher losses in the power distribution network, and additional stress on electrical equipment. Power factor correction techniques are used to improve power factor and optimize energy usage in AC circuits.