The following applet is copied from [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=313.msg1009#msg1009]RC circuit (DC: charge/discharge)[/url]
The charging circuit is R1 and C, the discharge circuit is R2 and C.
All the adjustable parameters can be control by those sliders.
The red dots represent the electrons.
The color of the capacitor is yellow (red+green) to represent neutral charge.
When electron enter one side of the capacitor, color for part of the region turn into red.
Another side of the capacitor lack of electron so it color turn into green.
You can charge the capacitor or discharge it.