How does impedance differ from resistance in electrical circuits?

Impedance is a comprehensive measure of the opposition that a circuit presents to alternating current (AC), and it encompasses both resistance and reactance. Whereas resistance focuses solely on how much a component opposes current, resulting in energy dissipation as heat, impedance broadens the concept to incorporate reactance, which accounts for the effects of inductance and capacitance on the flow of current.

In AC circuits, inductive components (coils) create reactance by opposing changes in current, while capacitive components (capacitors) oppose changes in voltage. This means that while resistance remains constant regardless of frequency, impedance varies with both the frequency of the current and the circuit components involved. As a result, impedance can change in magnitude and phase, which is fundamentally different from resistance.

Resistance is one part of impedance, but it does not include the effects caused by inductive or capacitive elements, which is why resistance alone cannot fully describe the behavior of circuits where AC flows. Understanding this distinction is crucial for working with AC circuits, where calculating total impedance is necessary for predicting circuit behavior accurately.