What does the term "impedance" refer to in AC circuits?

Impedance in AC circuits represents the total opposition that a circuit presents to the flow of alternating current. This opposition comprises both resistance, which is the opposition to direct current flow, and reactance, which arises from the inductive and capacitive elements in the circuit. The inclusion of reactance is particularly significant because it accounts for how AC circuits behave differently from DC circuits — inductors and capacitors can store and release energy, affecting the phase relationship between voltage and current.

Understanding impedance is critical in AC circuit analysis, as it helps determine how much current will flow for a given voltage according to Ohm's law applied in the context of AC. Impedance is commonly expressed as a complex number, where the real part represents resistance and the imaginary part represents reactance. This comprehensive understanding of impedance allows engineers and technicians to design and troubleshoot AC circuits effectively, ensuring the desired performance of electrical systems.