Is impedance a measure of a circuit's overall opposition to voltage?

Impedance is indeed a measure of a circuit's overall opposition to alternating current (AC), but this does not apply to direct current (DC) circuits in the same way. In AC circuits, impedance takes into account not only the resistance (which is the opposition to current flow) but also the effects of inductance and capacitance, which can cause the current and voltage to be out of phase. This results in a more complex opposition to the flow of electrical energy, which is quantified as impedance.

In contrast, in a DC circuit, the concept of impedance does not apply in the same manner because the current and voltage are in phase and only resistance is considered as opposition. Therefore, the assertion that impedance is a measure of a circuit's overall opposition to voltage can be misleading when referring to all types of circuits without specification.

Given this understanding, it is clear that stating that impedance is a measure of a circuit's overall opposition to voltage in a broad sense is not accurate, as it applies primarily to AC circuits.