A
Faraday cage or
Faraday shield is an enclosure formed by
conductive material or by a mesh of such material, used to block
electric fields. Faraday cages are named after the English scientist
Michael Faraday, who invented them in 1836. A Faraday cage operates because an external electrical field causes the
electric charges within the cage's conducting material to be distributed such that they cancel the field's effect in the cage's interior. This phenomenon is used to protect sensitive electronic equipment from external
radio frequency interference (RFI). Faraday cages are also used to enclose devices that produce RFI, such as
radio transmitters, to prevent their radio waves from interfering with other nearby equipment. They are also used to protect people and equipment against actual electric currents such as
lightning strikes and
electrostatic discharges, since the enclosing cage conducts current around the outside of the enclosed space and none passes though the interior.