What does capacitive reactance measure?

Capacitive reactance measures the opposition to a change in voltage across a capacitor in an alternating current (AC) circuit. This concept is crucial in understanding how capacitors behave when subjected to varying electrical signals. Unlike resistors, which dissipate energy as heat, a capacitor's reactance reflects its ability to allow or impede the flow of current based on the frequency of the AC signal. The reactance decreases with increasing frequency, meaning that at higher frequencies, a capacitor offers less opposition to changes in voltage, allowing more current to flow.

This concept is fundamental in circuits where capacitors are used for filtering, timing, and other AC applications. By effectively measuring the opposition a capacitor presents to changes in voltage, it becomes easier to predict how the capacitor will behave in a circuit, enabling designers and engineers to make informed decisions regarding circuit performance and stability.