Which letter represents impedance in electrical circuits?

Impedance in electrical circuits is represented by the letter Z. Impedance is a complex quantity that measures how much a circuit opposes the flow of alternating current (AC) and combines both resistance (R) and reactance (X) in its calculation. It is expressed in ohms, similar to resistance, but includes both the resistive and reactive components of a circuit, allowing for a fuller understanding of how the circuit behaves in an AC environment.

In contrast, R typically stands for resistance, which only accounts for the opposition to current flow due to resistive elements in the circuit, and does not include any reactance effect from inductors or capacitors. X is used specifically to represent reactance, which may be either inductive or capacitive but does not account for resistance. C, on the other hand, often denotes capacitance in electrical terms and is not related to impedance. Thus, the definition and functional role of Z in circuit analysis makes it the correct representation of impedance.