MadSci Network: Physics |
There are two things to consider, concerning what will give an unpleasent or even painful, posibly deadly electric shock; namely, voltage and current. Nicholi Tesla showed that several hundred thousand volts could run through a human being safely if at high frequency (alternating current) or very low current (low amperage, in the micro ampere range). Tesla coils and Van De Graff generators, which generate very high voltage in the hundred thousand volt range but at very low amperage are excellent at demonstrating this. In fact, some scinece exhibits such as the Franklin Institute in Philadelphia have a great deal of fun with the crowds using a Van De Graff generator which can throw an electric arc several feet to your hand without hurting you. And if fifty people are holding hands they all feel the jolt. A Van De Graff generator is very easy to build from home junk parts and the design can be had by searching around any high school or local library. Begin by looking through science projects books in physics. This is an excellent science project, I would know because my brother and I built one when we were kids (they really freak cats out because it makes their hair stand strait up from several yards away). A Van De Graff generator sort of looks like a UFO on a pedastool. In the dark, the static which coats the surface (which actually qualifies as a plasma) glows and discharges into the air in an eery way. Tesla coils, on the other hand, are a bit more involved to build safely and I'd wait a few years on that one. As far as amperage goes, I believe a standard 9 volt battery has a current output of about a hundred milliamperes - which at 9 volts just seems to hit the threshold of pain, safely (you ever heard of tongue testing a battery?). A car battery is only 3 more volts, at 12 volts, but has an output of several amps and can seriously burn through flesh. I can't think of any other common examples of low voltage-high current off the top of my head, but the basic principle is that the current, measured in amperes, which indicates the amount of electrons flowing, is what actually determines the... severity of the shock, not the voltage. Try building the Van De Graff generator, they're a lot of fun to play with. I just searched and found a web site at: http://www.seorf.ohiou.edu/~xx053/science/vandegraff.html which gives all the info you need to know and build a VDG. Havefun.
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