In electrical circuits, what does impedance measure?

Impedance is a fundamental concept in electrical circuits, particularly in alternating current (AC) systems. It measures the total opposition to the flow of alternating current. This opposition not only includes the pure resistance in the circuit, which impedes current flow regardless of the type of current, but also incorporates reactance. Reactance arises from capacitors and inductors in the circuit, impacting how the circuit responds to changes in current.

In essence, impedance combines both resistance and reactance, represented in complex form, allowing for a more complete understanding of how AC circuits behave as a whole. It’s crucial for calculating circuit characteristics like phase angles and currents that vary with time in AC systems. Therefore, choosing the option that identifies impedance as the total opposition to alternating current is accurate and reflects how it governs the circuit's behavior.