In which type of circuit do capacitors block current once charged?

Capacitors are components that store electrical energy in an electric field. In a DC circuit, once a capacitor is fully charged, it reaches a point where it cannot allow further current to flow through it. This happens because the voltage across the capacitor becomes equal to the voltage of the DC supply, and at this point, the capacitor behaves like an open circuit. Thus, in a DC circuit, after charging, the capacitor effectively blocks any further flow of current.

In contrast, in an AC circuit, the voltage varies constantly, and as a result, the capacitor continuously charges and discharges in synchrony with the alternating current. This allows current to flow through the capacitor, albeit in a manner that alternates direction due to the nature of AC.

Therefore, the correct answer focuses on how a capacitor behaves uniquely in a DC circuit by ceasing current flow once it has charged fully.