Re: faraday cage questions (fwd)

["High Voltage list" <hvlist@xxxxxxxxxx>]

Original poster: Steven Roys <sroys@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Tue, 02 Jan 2007 07:25:23 -0800
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: faraday cage questions (fwd)

At 07:23 PM 1/1/2007, you wrote:
>Original poster: Steven Roys <sroys@xxxxxxxxxx>
>
>
>
>---------- Forwarded message ----------
>Date: Sat, 30 Dec 2006 15:49:09 -0600
>From: Steve Ward <steve.ward@xxxxxxxxx>
>To: High Voltage list <hvlist@xxxxxxxxxx>
>Subject: Re: faraday cage questions (fwd)
>
>Jim,  To clarify, you are saying that the magnetic fields produced
>within the cage are "OK" provided that the cage is not the return path
>for this current?

Exactly.  Consider a Marx inside the cage.  If the Marx discharges to 
the cage, and the return path is through the cage, inevitably, some 
amount of the current is going to flow on the outside of the cage and 
radiate (especially if the cage is woven wire).

OTOH, if the entire current path is inside the cage (with no current 
flowing in the cage), then the cage can do its shielding function (at 
least for higher frequencies), and if some of the cage current (and 
there will be some... that's how the cage does the shielding.. a 
current of opposite sense is induced in the cage wall) does propagate 
to the outside, it is smaller in magnitude.