In an AC circuit, when does current flow into a capacitor?

Current flows into a capacitor during the time that the voltage across its terminals is rising. This occurs because a capacitor stores electrical energy in the form of an electric field, and this process requires a change in voltage.

When the voltage is increasing, it means that there is a difference in potential between the plates of the capacitor. This difference causes electrons to flow onto one plate, creating a positive charge on the opposite plate. Therefore, while the voltage is on the rise, the capacitor is allowing current to flow, as it is actively charging.

In contrast, if the voltage were constant, there would be no change in electric potential and thus no current flow into the capacitor. Additionally, if the voltage is falling, the capacitor would discharge instead of charge, leading to a flow of current out of the capacitor. The scenario where the voltage is capsizing is not accurate in the context of capacitor behavior, as it does not clearly define a specific condition relevant to current flow. Thus, the correct understanding hinges on recognizing that current is only introduced into the capacitor while there is a rising voltage.