Ham Amateur Radio Technician 2025 – 400 Free Practice Questions to Pass the Exam

Impedance is a measure of how much a circuit resists the flow of alternating current. It is represented as a complex number, consisting of a real part (resistance) and an imaginary part (reactance). The real part of impedance corresponds to the resistance in the circuit, while the imaginary part corresponds to the reactance.

In a purely resistive circuit, the impedance is wholly composed of resistance, which means that there is no reactance involved. This results in the impedance being purely real, with the imaginary component being zero. Therefore, when we analyze a purely resistive circuit, it exhibits characteristics where voltage and current are in phase and the reactive power is absent. This leads to a straightforward calculation and understanding of the circuit behavior since the power factor is 1.

Other scenarios may involve either reactance or a mix of resistance and reactance, which result in an impedance that includes both real and imaginary components, preventing it from being purely real. For instance, resonance can lead to the reactive components cancelling each other out, but it may still not be considered purely real if any resistance is present.