Faradays cage

[ionlylooklazy]

Main Question or Discussion Point

can a faradays cage be used to block external magnetic fields from interfering with the contents of the cage?

 

[david90]

yes. For example coax cables.

 

[berkeman]

can a faradays cage be used to block external magnetic fields from interfering with the contents of the cage?

Nope. A Faraday cage is used to shield against electric fields, not magnetic fields. To shield against DC and low-frequency magnetic fields, you need to use a high-mu ferrous material (like netic and conetic metals), which diverts the magnetic field around the sensitive area. See the following website for details:

http://www.magnetic-shield.com/

If the magnetic field is high-frequency AC, then you can get some shielding from a conductive material, as long as it is thicker than a skin depth at the AC frequency, and as long as the induced current in the shield has a full path to travel around the object to be shielded. So the orientation of any seams in the shield is important -- the seams have to be orthogonal to the magnetic field vector, so that the induced currents run parallel to the seams.

 

[Intuitive]

can a faradays cage be used to block external magnetic fields from interfering with the contents of the cage?

By using High Mu ferrous metal as a plate envelope is effective.

If you put a clear coat insulator over the plate shield you can make an even more effective envelope by laminating the shielding so the High Mu plates don't touch like, |||||, where there's a gap between magnetic shielding.

This will lower any possible chances for field inductions that emit past the shields saturation point.

Using two laminated High Mu shields is usually enough to lower Magnetic fields dramatically unless your working with tesla fields then you need better shielding, You can use many layers of the High Mu shielding, Super conductors also work, But, Both will still have Saturation points inwhich they will be ineffective.

I know this only because I put custom speakers in a Television one time and had to customize my own Magnetic shields to protect my Television tube.

Hands on experimenting.