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Magnetic shielding
Intermediate
High-permeability material diverts field lines.
High-permeability materials such as mu-metal divert field lines around a region, shielding it. Superconductors expel fields. Simple conductors only shield changing fields.
Shielding CRTs and sensitive instruments.
Static fields can't be shielded by copper.
In more detail
Magnetic shielding uses materials of high permeability to guide magnetic field lines away from sensitive equipment. Mu-metal is commonly used for this purpose.
Real-world uses
- Sensitive instruments such as electron microscopes are shielded from stray fields.
- Magnetic resonance rooms use shielding to keep external fields out.
- Engineers protect sensitive instruments and transformers by enclosing them in high-permeability metal shields.
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Frequently asked questions
How does mu-metal work?
It has very high permeability, so field lines prefer to travel through it rather than the interior.
Does a copper shield work too?
Copper shields electric fields and high frequencies, but it does not guide static magnetic fields well.
How does a shield block a magnetic field?
The shield draws the field lines into its material, which keeps the field away from the enclosed region.
Related topics in Magnetism & Induction
Magnetic energy density · Magnetic pressure · Lorentz force law