Scientists Say

Scientists Say: Faraday cage

This is a fence that keeps electricity out

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These girls are standing inside a Faraday cage. They are protected from the electricity zapping on the outside.

Antoine Taveneaux/Wikimedia Commons (CC BY-SA 3.0); adapted by L. Steenblik Hwang

By Bethany Brookshire

Faraday cage (noun, “FARE-ah-day cage”)

This is a box made of a material that blocks electromagnetic fields. A metal that conducts electricity, such as copper is used to construct the cage. When electricity — or certain types of electromagnetic radiation — hits a Faraday cage, the metal distributes the charge around the box. That protects whatever (or whoever) is inside.

Scientists build Faraday cages to protect very sensitive experiments. But Faraday cages don’t have to be cages or boxes. Some people line bags or wallets with metal mesh to make a small Faraday cage to protect their smartphone or laptop. And an elevator can sometimes act like a Faraday cage. That’s why your phone might lose signal inside.

The Faraday cage is named after its inventor, Michael Faraday. He made the first Faraday cage in 1836. He built a large box and lined it with wire mesh. To test his invention, Faraday zapped it from the outside with electricity while he stood inside.

In a sentence

City birds get confused by electromagnetic fields — unless they’re perched inside a Faraday cage.

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birds     Warm-blooded animals with wings that first showed up during the time of the dinosaurs. Birds are jacketed in feathers and produce young from the eggs they deposit in some sort of nest. Most birds fly, but throughout history there have been the occasional species that don’t.

copper     A metallic chemical element in the same family as silver and gold. Because it is a good conductor of electricity, it is widely used in electronic devices.

electricity     A flow of charge, usually from the movement of negatively charged particles, called electrons.

electromagnetic     An adjective referring to light radiation, to magnetism or to both.

electromagnetic radiation    Energy that travels as a wave, including forms of light. Electromagnetic radiation is typically classified by its wavelength. The spectrum of electromagnetic radiation ranges from radio waves to gamma rays. It also includes microwaves and visible light.

Faraday cage     A screening or other metallic enclosure, sometimes shaped like a box, to distribute an electrical charge associated with electromagnetic radiation around some protected area. This prevents the electrical charge from getting in, where it might destroy or disrupt fragile electronics (such as computer chips). The system is named after chemist Michael Faraday , who made pivotal early discoveries about the nature of electricity.

field     A region in space where certain physical effects operate, such as magnetism (created by a magnetic field), gravity (by a gravitational field), mass (by a Higgs field) or electricity (by an electrical field).

metal     Something that conducts electricity well, tends to be shiny (reflective) and malleable (meaning it can be reshaped with heat and not too much force or pressure). 

smartphone     A cell (or mobile) phone that can perform a host of functions, including search for information on the internet.

About Bethany Brookshire

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.