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Unread 22-12-2006, 09:19
Richard Wallace's Avatar
Richard Wallace Richard Wallace is offline
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Re: What to do with big capacitors?

Quote:
Originally Posted by Doug G View Post
If charged up at the max rating of 40 VDC - I don't think they will cause anyone that much harm. Resistance of people is on the order of 50,000 ohms - 500,000 ohms. Ohms Law says Current = Volts/Resistance, therefore... at 40 Volts and 50,000 Ohms, Current should be around 0.0008 Amps, which won't do much. It won't get your attention until you get up to 10 mA or higher. Maybe on your tongue will the resistance be low enough to give a good tingle. I use .1 Farad capacitors in my physics class and we charge them up with 9 V and the kids handle them without any shocks; they like putting tin foil on the terminals and watching sparks.
Human body resistance can be as high as you say, but can also be much lower depending on conditions. Look here or here for some interesting discussion and examples.
Quote:
Originally Posted by Doug G View Post
Power stored in a Capacitor is P = 1/2 * C * V^2, so 1/2 * .025 * 40^2 = 20 W in each Cap if its fully charged up to 40 V.
You mean energy, not power. The formula above gives stored energy in Joules. And 20 Joules is more than enough to stop your heart under the right (er, wrong ) conditions.
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I believe in intuition and inspiration. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.
(Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97)
 


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