Why does a Capacitor Block DC current and allow AC current to flow?

An electronic component known as a capacitor has the ability to stores electrical power in the form of an electric field. It comprises of two conducting plates separated by a dielectric, an insulating substance. The capacitor charges when a voltage is put across the plates, and it discharges when the voltage is removed.

Based on its charging & discharging characteristics, a capacitor’s function with respect to DC (direct current) & AC (alternating current) can be explained:

1) . Capacitors block DC

A capacitor starts to charge when a steady DC voltage is provided, continuing to charge until its maximum voltage is reached. The capacitor, however, functions as an open circuit for the DC signals after it is fully charged. This is due to the fact that in a steady-state, a DC circuit’s capacitor does not experience current flow. The dielectric substance effectively blocks DC signals by obstructing any additional current flow.

2). Capacitor passes AC

AC signals, in opposition to DC, alternate their polarity constantly throughout time. A capacitor will repeatedly charge and discharge when an AC voltage is supplied to it while the voltage changes its direction. The capacitor charges & stores energy throughout each half-cycle when the voltage increases, and it releases that energy when the voltage is decreased. This indicates that the capacitor in an AC circuit experiences a constant back-and-forth current flow. As a result, the capacitor permits the passage of AC signals.

While passing AC signals, capacitors may have varying impedances (resistance to the passage of AC current) at various frequencies. This can have an impact on how AC signals functions in a circuit. The AC signal frequency has an inverse proportional with a capacitor’s impedance, which has a direct proportional with capacitance. Numerous electronic applications, including filtering & coupling in AC circuits, make advantage of this feature.