What is a Faraday Cage?

Michael Pollick
Michael Pollick

It's very likely you woke up this morning in a Faraday cage, made your breakfast in another one, and drove one to work. Depending on your particular job, you may have spent much of your day in front of yet another Faraday cage.

Faraday cage with bolt of electricity.
Faraday cage with bolt of electricity.

The concept of a Faraday cage is logically attributed to Michael Faraday, a 19th century pioneer in the field of electromagnetic energy. Faraday studied the work of earlier scientists such as Benjamin Franklin and theorized that electromagnetic waves naturally flowed around the surface of conductive materials, not through them. For example, if a metal box containing a mouse were placed directly in the path of an electrical current, the electricity would flow over the box but not into the compartment with the mouse. The mouse would not be electrocuted. Such a box would be considered a Faraday cage.

Faraday studied the work of Benjamin Franklin when making his theory.
Faraday studied the work of Benjamin Franklin when making his theory.

The important concept to remember is that a Faraday cage acts as a shield against the effects of electromagnetic energy. When a car is struck by lightning, the metal frame draws the electricity away from the passengers inside. A microwave oven's door has a screen which prevents electromagnetic energy from escaping into the room. Electronic parts which generate radio frequencies are often protected by Faraday cages called RF shields. Even a concrete building reinforced with lead or rebar can be considered a Faraday cage.

Few consumers of electronic products would ever ask the sales clerk for a Faraday cage, but designers and engineers understand the importance of electromagnetic shielding very well. Whenever sensitive electronic parts are used in machinery, some form of shielding is generally in place, whether it be the machine's metal shell, a capsule or a grounding wire. If the electronic parts generate electromagnetic energy of their own, a Faraday cage must be used to shield users from excessive exposure. This is why cell phone use is often discouraged in hospitals or other public places with electronic equipment. Unshielded equipment may be exposed to the microwave energy created by cell phones or other radio transmitters.

Michael Pollick
Michael Pollick

A regular wiseGEEK contributor, Michael enjoys doing research in order to satisfy his wide-ranging curiosity about a variety of arcane topics. Before becoming a professional writer, Michael worked as an English tutor, poet, voice-over artist, and DJ.

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Discussion Comments


I have a question. Over the past year I have gone through a lot which has caused me to study and read more and here I am.

Long story short: I have seen neon green outlines of people in my backyard and in trees during a sunny day! At night, I've seen wavelengths throughout my back yard. Can anyone help me? I don't drink or do drugs and I'm not crazy. I know what I saw.

Please help me understand. Please ask me any questions if you need to. It has affected my life, family, work with the stress this has put on me.


@MrsPramm - I was in a car in the middle of a lightning storm once and I really wish I had known at the time that we were safe from harm. I can remember thinking that the lightning was so close we were sure to be electrocuted any second and I was absolutely terrified.

I don't know if I would have been completely calm if I'd understood the science, but I think it would have been a bit less of a heart attack inducing ride.


The concept of a faraday cage is often used in science fiction as a way to defeat some kind of weapon or power. It's basically used as a kind of buzz word, since people have heard of it, but probably don't know what it is.

I've seen it on TV as well, where the characters will explain that they need to find the perfect faraday cage and will spend the rest of the episode searching for one. When, as it says in the article, in reality cars and microwaves and many other enclosures are faraday cages. It's a standard way of protecting from lightning strike.


It is a metallic enclosure and it anticipates the entry or escape of an electromagnetic area. It has enclosure blocks non-static electric and external static fields. An ideal faraday cage is made up of an unbroken and perfectly conducting shell.


I'd like to ask where is it possible to find a truck with an F-shield to make, forwarding from Europe to Russia?


Cell phones. Microwave radiation. I think not. Try radio waves -- longer lambda and low_ E.


You can wrap your phone in an aluminum foil so nobody can call you. I tried it, and it works!


i got really stuck on my physics homework and this came in really handy.


If I suspend a water tight container in the middle of a 10x10x10 foot diving well using non conductive rope will that afford protection from all kinds of EMP? Thanks.


Would grounding a painted aluminum screen with fiberglass screen mesh enclosure suffice as a Faraday cage?


By using a brass screen, you can make an enclosure in which you cannot send or receive calls, yet you can actually see into it or out of it.


make a faraday cage or a room made completely of metal.


How can you make a room that you cannot accept or make cell phone calls out of?

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