On Fri, 28 Oct 1994 14:29:36 +0000, you said: > Unfortunately, if I remember rightly, a 220farad capacitor would have to be > about the size of Europe. Or am I wrong...
Take the smallest 100 microfarad capacitor you have ever seen. Imagine a capacitor that is 130 times as high and has 130 times the diameter. That would be a 220 farad capacitor. It's probably about the size of a dustbin. So yes, you are wrong. :-) Maybe we should actually ask Frode how big his capacitor is... :-) BTW, there are different types of capacitors. The most basic are the good old plates of metal separated by an insulator. Most capacitors below 1 microfarad are this type. If the insulator is SiO2 (which is what mica is), then the capacitance is roughly 3.48E-11 times the area divided by the separation distance. You would need a square of mica which measures about 3.7 km on each side to make a 1 farad capacitor assuming that the mica is 0.5mm thick. But most capacitors of 1 microfarad and above are electrolytic capacitors which have a much greater capacity than insulator- sandwich capacitors by virtue of the fact that they are able to store the charge chemically. There may well be a method for making extremely large capacitors which is even more efficient than that (Rechargeable batteries are a special case because they do not have the same charge-vs-voltage curve as "real" capacitors). imc
