EMF Shielding: Examining the Effects on Static Magnetic Fields

[Efthimios]

Your opinion to the following will be appreciated

Lets imagine a sphere made of a conductor (copper) placed within a
static magnetic field. The field will penetrate the within the shier.
Next we place inside the sphere a coil producing a variable
electromagnetic field. The electromagnetic field can not escape out
side the sphere due to shielding effect of the cooper sphere.

The question is: Taking in consideration the shielding effect created
by the variable electromagnetic field within the shier, can the static
magnetic field penetrate within the shier?

 

[Helmut Wabnig]

On Wed, 31 Oct 2007 05:51:35 +0000 (UTC), Efthimios
<eangelopoulos@gmail.com> wrote:

>Your opinion to the following will be appreciated
>
>Lets imagine a sphere made of a conductor (copper) placed within a
>static magnetic field. The field will penetrate the within the shier.
>Next we place inside the sphere a coil producing a variable
>electromagnetic field. The electromagnetic field can not escape out
>side the sphere due to shielding effect of the cooper sphere.[/color]

A static magnetic field will remain unaffected.

For the variable em field the shielding effectiveness is limited.
There will be a certain amount of leaking through the shield,
dependent on frequency, wall thickness, conductivity, and so on.
We usually calculate damping factors in deziBel values, "dB".

>
>The question is: Taking in consideration the shielding effect created
>by the variable electromagnetic field within the shier, can the static
>magnetic field penetrate within the shier?[/color]

Yes, the two fields do not affect each other.
We cannot shield a static magnetic field by applying
a high-frequency radiation to the shield.

w.

 

[aarson]

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