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From: steveq@syd.dms.CSIRO.AU (Stephen Quigg)
Newsgroups: sci.electronics
Subject: Re: 3dB rolloff of a human (was Re: HELP!)
Message-ID: <1991Jan29.043048.24825@syd.dms.CSIRO.AU>
Date: 29 Jan 91 04:30:48 GMT
References: <20472@hydra.gatech.EDU> <2204@otc.otca.oz>
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In article <2204@otc.otca.oz> brendan@otc.otca.oz (Brendan Jones) writes:
**stuff deleted**
>In the studio, they had a Van Der Graff generator (I think), a horizontal
>circular anode that acted as a platform and about three metres above that 
>a pointed cathode.
>
>The generator was said to deliver 1 million volts EMF at a frequency of
>20 kHz.  The narrator then put on pointed thimble caps on the ends of
**stuff deleted**....
A Van de Graaf generator is DC. What you saw was almost certainly a Tesla
coil. This sort of demonstration was common before WW1.
**stuff deleted**
>So it goes to show that EMF is not the killer.  Current is, but obviously
>the body is a low pass filter and must have high attenuation at 20 kHz.
>So what is the 3dB rolloff?  I suspect around 100 Hz which is why 50 Hz
>is such a killer.
What was demonstrated was the "skin effect", where at high frequencies, current
tends to flow on the outside of the conductor only. Hence the nervous system
is not affected, and so the person is not electrocuted. Get the power density
up and you'll cook though; just ask any HAM operator about RF burns.
D