[Summary] Analysis of the principle of AC-DC isolation of capacitor

For DC, in the instant of the closed switch, the capacitor is connected to the positive electrode of the power supply, the positive charge is the majority,

The negative charge on the plate connected to the anode of the power supply is the majority, and the electric potential of each point in the circuit is equal immediately.

Therefore, the capacitor in the DC circuit can play a role in separating the DC.

In AC circuits, when the switch is closed, free electrons do not pass through the capacitor, except for alternating voltages,

Allows free electrons to move back and forth through the circuit on the two plates of the capacitor C2, and the relative motion of the free electrons forms the current,

This is why the capacitor communicates.