wildswing

This is only my second post here so please cut me some slack if I'm overstepping my "newbie" back bencher status. I'm an electrical technologist so I hope I can add to the correct info here. Most of what you guys are saying is correct except for the one statement about the current not going back to the battery during charging. I disagree with that.

When the capacitor is first connected (let's assume no test lamp or resistor) the cap looks like a dead short to the battery. Think of it as a simple series circuit, out of the battery, through the cap, then back to the battery. It's like a garden hose full of marbles. Put another marble in and one MUST fall out the other end. If it didn't, a cap would not have a second (-) terminal.

When it's first connected to the battery, the cap has no charge (no voltage drop across the cap), therefore there is no resistance to current flow. That means big instantaneous current. This current charges the cap. As the cap charges, the voltage across it's terminals increases. The caps polarity is opposite to the battery, thus it creates an opposition to the flow from the battery and the flow decreases. Once fully charged, the current flow stops.

If voltage of the circuit connected to the positive side of tha cap falls, the higher voltage within the cap forces current flow out of the cap. That's when it's doing it's job.

BassHamster

Dont worry, your not oversteping your bounds at all!
You're dead on! But inexperienced people here are going to try to tell you you're wrong. I went on a big rant about this in another thread. Oh well rant over. You Rock!