Which power factor indicates a load that consumes only real power without reactive power?

A unity power factor indicates that a load consumes only real power without any reactive power. In electrical systems, power factor is a measure of how effectively electrical power is being converted into useful work output. It is defined as the ratio of real power (measured in watts) to apparent power (measured in volt-amperes).

When the power factor is unity, it equals 1, meaning all the power being consumed by the load is being used effectively as real power, and there is no reactive power involved. Reactive power arises from inductive or capacitive elements in a circuit, which lead to energy being stored and released but not consumed. Therefore, a unity power factor signifies optimal efficiency in power usage with no waste in terms of reactive power components.

In contrast, other power factors, whether leading or lagging, indicate the presence of reactive power. A leading power factor usually occurs in capacitive loads, while a lagging power factor is seen in inductive loads. A zero power factor suggests that all the power is reactive, with no real power effectively being used for doing work. Thus, unity power factor is the only condition that meets the criteria set by the question.