Grumpy_Mike:
That is because the large electrolytic smooths the voltage and so the ripple voltage ( hence current ) that the ceramic is subjected to is a lot smaller.
Well here's another thing I don't understand. How does the electricity decide to flow into the larger cap first, to reduce the ripple the smaller one sees?
I would assume both caps would see the same dip in voltage, and both would react simultaneously to correct for it.
In other words, let's say you had a power rail that was oscillating between 4.95V and 5.05V. If you connect the small cap, it tries to stabilize the voltage, but the current being drawn is so high that it's voltage is just swinging wildly back and forth. Now you connect the large cap, and with it's larger capacity it can supply the necessary current, so the voltage doesn't drop as much...
And ah, I think I get what's going on now. The small cap stops swinging so wildly back and forth because the large cap is preventing the voltage swing from happening in the first place.
This also makes it easy to understand what happens when you have two caps that are identical. The capacitances add up the capacitors are capable of supplying more current, and thus more able to prevent the voltage from dipping, and so each dips half as far each cycle.
This of course assumes the cycles or spikes in voltage are short enough that the capacitors don't drain completely.
If they did... I suppose I'd calculate how much current the capacitors are supplying based on their Farads? Or... would they never drain completely because even if the voltage dips to 4.95V and stays there, one side of the capacitor is at 4.95V and the other side is still at 0V, so technically it's oscillating with only a fraction of it's full capacity?
Now I've gone and confused myself again.