Definition: Faraday cage

A shielded enclosure used to block electromagnetic fields from reaching its interior. However, a compass does work inside a Faraday cage because the cage does not block the earth's magnetic field. Constructed of a metal mesh, current is conducted on the cage itself. It was invented by physicist Michael Faraday in 1836.

Buildings that house sensitive test equipment and hospital MRI rooms may be enclosed in Faraday cages. They are also used to prevent eavesdropping. Home-made cages are made by wrapping a cardboard box with aluminum foil or using metal garbage cans or anti-static bags. Items placed inside can also be wrapped with layers of aluminum foil. See radiation shielding, air gapped, EMP and Farad.

Temporary Shielded Enclosures

Providing the type of shielding that Faraday cages offer, these portable tents eliminate electromagnetic interference (EMI). They are also easy to set up and tear down. (Images courtesy of Select Fabricators, top, and TekBox Digital Solutions, bottom.)