What does impedance measure in an AC circuit?

Impedance is a crucial concept in alternating current (AC) circuits, as it quantifies the total opposition that a circuit presents to the flow of electric current. This total opposition is not merely a function of resistance; it also encompasses reactance, which represents the opposition to current flow due to the presence of inductors and capacitors in the circuit.

In more detail, resistance accounts for the energy dissipated as heat in the conductors, while reactance accounts for the energy stored in the magnetic and electric fields of inductors and capacitors, respectively. Therefore, impedance is a complex quantity represented by both a magnitude (which is measured in ohms) and a phase angle, which reflects the relationship between voltage and current.

Understanding impedance is essential for analyzing how circuits respond to AC signals, as it influences factors such as phase shifts and resonance, and ensures proper functioning of AC circuits at varying frequencies. This distinction highlights why options referring specifically to power, voltage drop, or energy consumption do not accurately describe what impedance measures.