In terms of power factor, which value represents a purely resistive circuit?

A purely resistive circuit is characterized by a power factor of 1. This means that the voltage and current are in phase, signifying that all the power supplied by the source is being used effectively as real power. In such a circuit, there is no reactive power since there are no inductive or capacitive components present that can store energy temporarily.

Having a power factor of 1 indicates that the circuit converts electrical energy into work (thermal energy in the case of resistors) without any losses due to energy storage and release, which is typical in circuits with reactive elements. In summary, a power factor of 1 is indicative of a purely resistive load where the energy flow is efficient and solely utilized for the intended purpose, without any phase difference between voltage and current.