What does electrical impedance measure?

Electrical impedance is a comprehensive measurement that quantifies the total opposition a circuit presents to the flow of alternating current (AC). It encompasses not only resistance, which is the opposition to current flow in an electrical circuit, but also reactance, which is the opposition caused by capacitors and inductors in an AC circuit.

When analyzing AC circuits, impedance is represented as a complex number that combines both the resistive and reactive components. This means that impedance not only takes into account how resistors affect current flow but also how inductors and capacitors temporarily store and release energy, altering the effective opposition to current flow.

In contrast, the other options do not accurately describe the concept of impedance. The total voltage in a circuit is a measure of electrical potential and does not directly relate to how resistance or reactance affects AC current. The opposition to direct current flow specifically refers to resistance, and while resistance is a part of impedance, it does not include reactance. Lastly, the efficiency of electrical components involves how effectively they convert electrical energy into useful work, which is unrelated to the concept of impedance itself.