Re: Magnetic Force with Tesla Coil?

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

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


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, July 09, 2004 6:35 AM
Subject: Re: Magnetic Force with Tesla Coil?


 > Original poster: "Bob \(R.A.\) Jones" <a1accounting-at-bellsouth-dot-net>
 >
 > Hi,
 >
 > Actually the magnetic field will only penetrate to a skin depth(1/e) of
the
 > material at the relevant frequency.

This isn't precisely true.  The skin depth represents a depth where IF the
current distribution were uniform, would have the same total current as the
real thing. That is, the total current is equal to d * current density.   In
reality, the current (or field) tapers off as exp(-d/skindepth).  At the
"skin depth" the magnitude of the current (not the phase!) is exp(-1) (about
37%), but the current still extends deeper (theoretically to infinity). so
the total current is integral(0to infinity) [d * J(d)]dt (Where J(d) is the
current density). Since, in uniform materials J(d) = exp(-kd), you can make
use of the fact that integral(0to1) exp(-x)dx = 1.