what is magnetic shielding...????

Magnetic shileding is the process of protecting an instrument from external magnetic fields. In these cases shields made of high magnetic permeability metal alloys can be used, such as sheets of Permalloy and Mu-Metal(with relative permeability values of 80,000 to 100,000) or with nanocrystalline grain structure ferromagnetic metal coatings.These materials don't block the magnetic field, as with electric shielding, but rather draw the field into themselves, providing a path for the magnetic field lines around the shielded volume. The best shape for magnetic shields is thus a closed container surrounding the shielded volume.

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