Re: math woes

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

At 10 kHz with the semiconducting nature of the body, the skin depth will be
huge (comparable to the size of the body), so conventional formulae won't
work.  The classical formula is for the depth in an infinite flat sheet.
For any reasonable sized round conductor (where the "infinite flat plate"
skin depth is a significant fraction of the radius (say >.1 r) ), there is a
correction factor that needs to be applied.

Classical formula: skin depth(meters) = sqrt(rho/(pi*f*mu))
mu = 4*pi*1E-7 Henry/meter for free space and nonmagnetic materials
rho = resistivity in ohm meters
f = frequency (Hertz)

So, for your example: mu = 4 pi 1E-7, rho = 70, f = 1E4
=sqrt(70/(4*3.14159E-7 * 1E4 * 3.14159)) = 42 meters?

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, November 26, 2001 7:56 PM
Subject: math woes


> Original poster: "J.R. Galen by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jrgalen-at-earthlink-dot-net>
>
> I'm terrible at math, and worse at applying it.
>
> I want to find the skin depth penetration of certain diameters of human
body
> parts in centimeters(thumb, chest) using a resistivity of 40 ohm-meters
for
> skin covered flesh and then 70 for open flesh, and using 10,000hz.
>
> I've got the formula, but am having difficulty as I don't grasp it, and
I've
> seen two versions.  I'd much appreciate if someone (very patiently and as
if
> you were explaining to a sixth grader) could just map out in a formula
where I
> would plug in what, (and in what units) and how I can change the result to
> centimeters?
>
> I'd appreciate the help.  (This is not homework, I'm 43, and tesla
fascinated
> but inept.)
>
> renee
>
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