What defines the term "impedance" in an electrical circuit?

The term "impedance" in an electrical circuit refers to the overall opposition that a circuit presents to the flow of electric current, particularly in alternating current (AC) circuits. This concept encompasses not only the resistance, which is the opposition to direct current (DC), but also the impact of reactance, which arises due to capacitance and inductance in the circuit.

Impedance is a complex quantity that is measured in ohms and is represented as a combination of real (resistive) and imaginary (reactive) components. While resistance (the real part) opposes the flow of current uniformly, reactance (the imaginary part) varies with frequency and plays a significant role in AC circuits due to the influence of inductors and capacitors.

This definition makes it clear that impedance is a comprehensive term that applies to both AC and DC conditions, though its effects are most significant in AC. Understanding impedance is essential for designing and analyzing circuits, ensuring that the correct voltage and current levels are maintained under varying conditions.