How-To Geek


What Widely Used Insulating Enclosure Is Named After a 19th Century Scientist?
The Tesla Shield
The Van der Graff Box
The Edison Sphere
The Faraday Cage

Answer: The Faraday Cage

Common in everything from research laboratories to television cables to server rooms in hardened government facilities, Faraday cages are a firmly enmeshed, yet seldom seen, part of our modern world.

A Faraday cage is simply an enclosure of a conductive material that blocks out external static and non-static electrical fields. What does that mean in layman’s terms? Anything within a properly designed Faraday cage will be perfectly insulated from outside electrical interference. You could, for a rather dramatic example, stand inside a Faraday cage at the top of the Empire State Building and every lighting strike that hit the cage would flow around the cage, leaving you completely unharmed inside.

As far back as 1755, Benjamin Franklin observed the phenomenon with experiments that suspended cork balls via silk threads within a metal container–the container effectively shielded the balls from the electrostatic charges applied to the outside of the container. At the time, however, there appeared to be no practical application for the phenomenon and Franklin paid little attention to it beyond noting it for posterity. Nearly a century later in 1836 Michael Faraday extended Franklin’s research by building large enclosures and subjecting them to high voltage discharges from an electrostatic generator. It is largely a matter of the time of discovery and first useful application of discovery that we call the resulting construction a Faraday cage instead of a Franklin cage.

So where do we find these Faraday cages in daily use today? Faraday cages are incorporated into all manner of structures, cabling, and even clothing. MRI rooms in hospitals are built to function as Faraday cages to cut down on external interference and improve the quality of the MRI scan. Coaxial cable is wrapped in a sheath-style Faraday cage to protect the core of the cable from interference. Lineman who work on high voltage electrical lines wear entire suits made of conductive mesh which allow them to work on 1000+ volt lines in complete safety–the current flows over their bodies like water flows over a fish.

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