Electromagnetism Resource

Apart from its strength, low price, resistance to fire, and ease of working, steel has two main advantages when making electrical enclosures

• high permeability means it's good for magnetic shielding; and
• being conductive, it blocks electric fields.

Both of these properties help reduce interference from electrical switchgear.

Enclosing equipment that is sensitive to magnetic disturbances (even the Earth's magnetic field can cause problems) within a high permeability enclosure is called magnetic shielding. The idea is to use the high permeability enclosure to divert magnetic fields around the sensitive device.

The picture below shows a box made of mu-metal a special alloy that is designed to magnetically shield a sensitive experiment.