What kind of current do capacitors block?

Capacitors are designed to block direct current (DC) while allowing alternating current (AC) to pass through. This behavior is due to the way a capacitor charges and discharges. When a DC voltage is applied across a capacitor, it will initially allow current to flow as it charges up to the voltage level of the source. Once fully charged, the current stops flowing because the capacitor acts like an open circuit for DC.

In contrast, when an AC voltage is applied, the voltage across the capacitor continually changes, allowing the capacitor to charge and discharge repeatedly. This cyclical charging and discharging process enables AC to pass through while blocking DC, which is why the correct answer focuses on direct current being blocked. Understanding the fundamental properties of capacitors, such as their reactance in AC circuits versus their behavior in DC circuits, is crucial for applications in electronics and circuit design.