Faraday cage

1836 Faraday cage

The book of science

Tom Sharp

Michael Faraday electromagnetism

Faraday cage

Corks and cans

Equilibrium in flux

An exterior electromagnetic field generates a current in an ungrounded Faraday cage to distribute electrons until the charged surfaces generate an opposing field to cancel the field inside the cage. Outside the cage, however, the field appears to travel through the cage.

A grounded Faraday cage still cancels an exterior field so that it has no effect inside the cage, but doesn’t make the cage seem transparent to the field, and it’s safe for someone on the opposite side of the field to touch the surface of the cage.

See also in The book of science:

Readings on wikipedia: