Why does a Capacitor Block DC but Allow AC?
A capacitor stores electric charge and allows current only while its voltage is changing. ●DC: The voltage becomes constant after the capacitor is fully charged, so dV/dt = 0. Hence, current becomes zero. Therefore, a capacitor blocks DC. ●AC: The voltage continuously changes with time, so dV/dt ≠ 0. The capacitor continuously charges and discharges, allowing current to flow. Therefore, a capacitor allows AC.