In an AC circuit that only contains resistance, what will the power factor be?

In an AC circuit that contains only resistance, the power factor is defined as the ratio of real power flowing to the load to the apparent power in the circuit. When there is only resistance present, all of the electrical power is actively used to do work (convert electrical energy into heat, light, or mechanical energy) without any reactive component. In this scenario, the power factor is 1, which can also be expressed as 100%.

This value indicates that the circuit is perfectly efficient in using electrical power, with no phase difference between voltage and current. In practical terms, a power factor of 100% means that all energy supplied is effectively used, which is typical for purely resistive loads like incandescent light bulbs or electric heaters.