What happens to AC signals in capacitive coupling?

In capacitive coupling, the primary function of a capacitor is to allow alternating current (AC) signals to pass while blocking direct current (DC) components. This occurs because a capacitor has a reactance that decreases with increasing frequency; thus, AC signals, which vary over time, can charge and discharge through the capacitor. As a result, AC signals effectively continue through the circuit while any steady DC voltage present is blocked, as it cannot flow through the capacitor.

This mechanism is essential in various applications, such as in audio electronics, where retaining the AC audio signal is crucial while preventing any DC bias from affecting the circuit operation. Capacitive coupling is widely used in signal processing and filtering circuits for this very reason.