We once calculated the conductivity of water as compared to copper and found that copper is something like 7000 times more conductive than water to electricity. I can't remember the exact figure or if this was AC or DC, but it does NOT mean that the human body (96% water) is an insulator! A little bit of knowledge can be a dangerous thing...I give this warning to everyone!

Regards, DPW [ Spent years making heaters out of op-amps.]

 

I haven't had time to do much figuring on this but two questions immediately spring to mind.

Firstly the electromagnetic waves of frequency greater than 200mHz would be smaller than a human (1.5m wavelength).

Secondly propagation of waves (=AC) depends upon the ratio of conduction current to displacement current in the medium concerned.

when ωε > σ propagation is capacitive ie the medium behaves as a dielectric.

I don't have figures for skin but seawater which should be similar

ε = 80 and σ = 4

I can reprint some data for muscle, from the book I mentioned above, at frequencies where the skin effect would start to become important.

f [MHz].......\(\sigma\) .................\(\epsilon_r\)..................p
--------------------------------------------------------------
1...............0.4 ..................2000................3.6
10.............0.63..................160 .................7.1
100...........0.89 ..................72...................2.2
1000..........1.65..................50...................0.59
10000.........10.3.................40...................0.46
100000........80....................6.....................2.4

The formula for skin depth for imperfect conductors like this is as follows.

\(\delta={{sqrt{2}}\over{\omega \sqrt{\mu \epsilon_r \epsilon_0 (sqrt{1+p^2}-1)}}}\)

 

I remember once when I was doing some TV service work for an old Norwegian TV shop owner; I didn't think the Flyback transformer was putting out any HV. He said I had plenty of voltage and with that grabbed a long (15") nutdriver and placed it under the tube anode connection and that HV crawled up the shaft into his hand. I still see that picture sometimes in my dreams. It was thrilling!

Regards, DPW

 

Yeah, I didn't intend for my 'anecdotal' reply on page 1 to be construed as any sort of guideline, hence the warning not to do it! That was merely what TESLA thought back in the infancy of AC/high voltage experimentation, say 1910. I'm the guy who stays at least 3' back from my Jacob's ladder, and I recommend that ANYONE treat all conductors as though they are energized until proven otherwise. A mild paranoia of high voltage and/or high current circuits keeps one healthy....