engineering question #2298



Rod, a 21 year old male from canterbury asks on October 10, 2004,

Q:

Is there any magnetic shielding material which is not itself attracted by a magnet?

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the answer

James Livingston answered on October 10, 2004, A:

No, if you are referring to shielding static (DC) magnetic fields. However, if you are interested in shielding high-frequency AC magnetic fields, any good electrical conductor, such as copper or aluminum, can provide good shielding if sufficiently thick. Applied AC magnetic fields induce "eddy currents" in the conductor which oppose the applied fields and prevent their penetration much beyond a frequency-dependent "skin depth."

Magnetically shielded rooms designed to shield ALL external magnetic fields use both a layer of magnetic alloy to shield DC and low-frequency magnetic fields and a layer of copper or aluminum to shield high-frequency AC fields.

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