How does a capacitor behave in an AC circuit?

In an AC circuit, a capacitor behaves as a reactive component that stores and releases energy.

Capacitors are passive components that store electrical energy in an electric field between two conductive plates. In an AC circuit, the voltage across the capacitor changes periodically, causing the capacitor to charge and discharge. When the voltage is positive, the capacitor charges up, and when the voltage is negative, the capacitor discharges. This charging and discharging process causes the capacitor to behave as a reactive component that opposes changes in voltage.

The opposition to voltage changes is known as capacitive reactance, which is measured in ohms. The capacitive reactance of a capacitor decreases as the frequency of the AC signal increases. This means that capacitors allow high-frequency AC signals to pass through while blocking low-frequency signals. Capacitors are often used in AC circuits to filter out unwanted noise or to block DC signals.

Capacitors also have a phase relationship with the voltage in an AC circuit. The voltage across a capacitor lags behind the current by 90 degrees. This means that the capacitor stores energy when the current is at its peak and releases energy when the current is at its minimum. The phase relationship between the voltage and current in an AC circuit is important for understanding the behaviour of capacitors and other reactive components.