What does impedance refer to in electric systems?

Impedance in electric systems specifically refers to the total opposition that a circuit presents to alternating current (AC). This concept encompasses not only resistance, which opposes current flow, but also reactance, which arises from capacitors and inductors in the circuit that impede the change of current and voltage over time.

Impedance is measured in ohms and is represented as a complex quantity that combines both resistance (the component of impedance that dissipates energy) and reactance (the component of impedance that stores and releases energy). This makes it crucial for analyzing and understanding how AC circuits operate, especially in the presence of varying frequencies.

In contrast, while resistance pertains exclusively to direct current (DC), impedance is broader and applies to AC systems. This distinction is essential for anyone studying electrical engineering or working with AC circuits, as it helps in designing and analyzing systems that utilize alternating currents effectively.