Which condition signifies that a circuit is purely resistive?

A circuit is considered purely resistive when the current is in phase with the voltage. This means that the peaks and troughs of the current waveform align perfectly with those of the voltage waveform. In practical terms, this condition indicates that all the power supplied by the voltage source is being used to do useful work in the resistive components of the circuit, resulting in no reactive power.

When the current and voltage are in phase, the power factor, which is the cosine of the phase angle between current and voltage, is equal to one, indicating maximum efficiency in the circuit. This is a fundamental concept in alternating current (AC) circuits, where the relationship between voltage and current can change depending on the components present (resistors, inductors, and capacitors) and their respective arrangements.

The other conditions mentioned do not represent a purely resistive circuit. For instance, if voltage leads current by 90 degrees, the circuit is purely inductive. A high power factor with out-of-phase voltage would indicate a scenario where there is some reactance present, further supporting that it's not purely resistive. Similarly, a power factor of zero would indicate a purely reactive circuit, where the voltage and current are 90 degrees out of phase, and thus,