How is "impedance" defined in the context of an AC circuit?

Impedance in the context of an AC circuit is defined as the total opposition to current flow, which includes both resistance and reactance. Resistance pertains to the opposition to direct current (DC) and remains constant across AC frequencies, while reactance can vary depending on the frequency of the AC current. Reactance arises from components such as inductors and capacitors, which store energy temporarily and affect the flow of alternating currents.

In practical terms, impedance is represented as a complex number, combining real and imaginary elements that account for both resistive and reactive effects in the circuit. This means that impedance affects both the magnitude and phase of the current flowing through the circuit. Understanding impedance is crucial for proper circuit analysis and design in AC systems, making it essential for anyone working with electrical and instrumentation applications.

The other options do not capture the comprehensive nature of impedance. Voltage alone does not account for how current is affected by circuit components, power consumption is just a measure of energy usage, and frequency describes how quickly the current oscillates rather than the opposition to current flow.