I'm a bit stuck on understanding capacitors properly. I can use them for the simple things, but without a clear understanding of exactly how they work.
First: if the current flowing into a capacitor is related to the change in voltage, wouldn't it always be empty in a simple parallel DC battery/capacitor/LED circuit? The voltage across the capacitor will be 0 volts before we power up the circuit; then, power is connected, and the voltage across the leads is now 9 volts (without any ramp-up time... or is this where the answer lies?).
I guess you could think of it as an infinite rate of change during an infinitely short time, but clearly the battery can't fill the capacitor in that time, if nothing else then due to internal resistance.
So... what actually happens here? Will the capacitor change fully (to 9 volts in this example)? Or not at all?
Second question: if we assume that the cap charges up well and nice, and we then remove the battery, causing it to discharge... Wouldn't the current from the capacitor be in the "wrong direction", passing onto the cathode of the LED, thus either doing nothing or possible causing damage to it?
As I'm sure you can see, I'm rather confused, and reading 10 different explanations of capacitors didn't quite sort that out, as most explain them in a near-identical way.
First: if the current flowing into a capacitor is related to the change in voltage, wouldn't it always be empty in a simple parallel DC battery/capacitor/LED circuit? The voltage across the capacitor will be 0 volts before we power up the circuit; then, power is connected, and the voltage across the leads is now 9 volts (without any ramp-up time... or is this where the answer lies?).
I guess you could think of it as an infinite rate of change during an infinitely short time, but clearly the battery can't fill the capacitor in that time, if nothing else then due to internal resistance.
So... what actually happens here? Will the capacitor change fully (to 9 volts in this example)? Or not at all?
Second question: if we assume that the cap charges up well and nice, and we then remove the battery, causing it to discharge... Wouldn't the current from the capacitor be in the "wrong direction", passing onto the cathode of the LED, thus either doing nothing or possible causing damage to it?
As I'm sure you can see, I'm rather confused, and reading 10 different explanations of capacitors didn't quite sort that out, as most explain them in a near-identical way.