Re: About the skin effect in humans

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Jim Lux <jimlux-at-earthlink-dot-net> 

At 08:19 AM 5/21/2004 -0600, you wrote:
>Original poster: "mercurus2000" <mercurus2000-at-cox-dot-net>
>I was just curious, I hear the skin effect in human beings still very deep 
>at standard tesla coil frequencies, does anyone here have references or 
>sources as to where the information is gathered about how deep currents 
>penetrate into the human bodies at different frequencies?
>Thanks,
>Adam
The standard equation for skin depth

The skin depth is the depth of a layer that if, the current were uniformly 
distributed, would carry the same current density as the whole thing. In 
the real thing, the current density falls off as exp(-x), so the classic 
definition of skin depth is where the current is 1/e (exp(-1)) that at the 
surface. (integrate e^x, etc., and you see that it works out...)


The depth is inversely proportional to the  square root of 
(conductivity*permeability*frequency)

In equations:

depth = c/sqrt(2*pi*sigma*mu*omega)

  c= speed of light (3E8 m/sec)
sigma = conductivity
mu = permeability (4*pi*1E-7 for free space/non magnetic substances)
omega = (2*pi*frequency)

Some qualitative observations:

Higher conductivity: smaller skin depth
Ferrous materials: smaller skin depth (why steel is a good shield for 
magnetic fields)
Higher frequency: smaller skin depth.