What type of circuit is primarily affected by impedance?

Impedance is a concept that specifically applies to alternating current (AC) circuits and is a measure of the opposition that a circuit presents to the flow of electric current. In AC circuits, impedance encompasses not only the resistance (ohmic resistance) but also the reactance, which arises from capacitance and inductance in the circuit. Reactance can vary with frequency, making it a critical factor in AC circuit analysis.

In contrast, direct current (DC) circuits are primarily influenced by resistance alone, as they do not involve changing frequencies or reactive components in the same way that AC circuits do. Open circuits and short circuits are conditions related to the flow of current but do not inherently involve the concept of impedance; an open circuit means there is a break in the circuit preventing current flow, while a short circuit presents a low-resistance path that can lead to excessive current flow. Hence, the type of circuit that is fundamentally based on the concept of impedance is exclusively AC circuits.