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How Does a Faraday Cage Work?

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Even if you didn’t know what one was, you’ve used Faraday cages before, and on a regular basis, I might add. You’ll find them at places like the hospital (MRI scan rooms), but you even have one at home in your very own kitchen. That’s right, microwaves function exactly like a Faraday cage but in reverse since the microwave holds the “waves” inside to cook your food without allowing them to escape.

But what’s the purpose of an actual Faraday Cage and why should you know about them? Well, have you ever heard of an EMP (electromagnetic pulse) attack before? Most preppers are familiar with EMPs and realize that type of terrorist attack could leave large swaths of our country not only defenseless but entirely in the dark. And that includes saying goodbye to your laptop, cell phone, your vehicle’s computers, and other electronic appliances and gadgets.

Lately, we’ve been hearing about attacks on the electrical grid. Those attacks were physical in nature with the attackers shooting transformers located within substations throughout the country. It’s sad, but most substations are conveniently located for access by utility companies, but also easily seen and approachable by perpetrators who want to raise havoc with a community’s electrical system.

Consider how challenging it would be to have a terrorist network or foreign power set in motion a huge electromagnetic pulse from a satellite, commercial aircraft, or missile. That pulse would have a very wide coverage area and any electronic device could be affected as the pulse damages sensitive components. Once hit by the pulse, the device(s) become inoperable and possibly damaged beyond repair.

How Does a Faraday Cage Work?

How Does a Faraday Cage Work?

A simple definition of a Faraday cage is: “A grounded metal screen surrounding a piece of equipment to exclude electrostatic and electromagnetic influences.” I don’t know about you, but it sounds pretty scary to have an EMP close by and not have any way to protect your electronic belongings.

But having a Faraday cage, you’d be able to protect your everyday electrical essentials, whether it’s your cellphone, computer, or something even as big as your pickup truck. Keep reading to find out what a Faraday cage is, how it works, and how your home could benefit from having one.

It’s important to understand terms like wavelength, radio frequency, conductors, voltage, and electroscope when you’re trying to understand the significant details of how a faraday shields electromagnetic waves! If you can think of how your microwave oven works, then you’ll have a good understanding of how the Faraday cage works.

What is a Faraday Cage?

If you didn’t know what a faraday cage was before reading this article, don’t feel too bad. Not many people do. As mentioned above, a Faraday cage is a protective enclosure that’s main purpose is to block out or shield the objects that are inside from any source of electromagnetic radiation. That being said, the cage keeps the electric charge on the outside without it ever traveling to the inside. In order for it to work, the material that is used to build the cage has to be something that can conduct electricity, like most metals.

Faraday cages have also been called Faraday pouches, boxes, or shields. A lot depends on the size and use of the Faraday unit.

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How Does a Faraday Cage Work?

Now that you have a better idea of what a Faraday cage is, let’s take a brief look at how one works. Let’s say you have a metal box. That box would act as an enclosure that is capable of blocking any external electromagnetic field(s) or radio waves from ever entering the inside. That metal box or shield makes it so the charge wouldn’t be able to penetrate through the metal walls because electricity would stay within and travel on conductive material, the metal walls of the box.

So, in order for electric fields and radio waves to be shielded, they would need something with zero electrical resistance so that the electrical charge or pulse can easily flow within the exterior of the cage (outer surface) walls without any interference to the interiors of the unit or its contents.

Could a Faraday Cage Really Protect from an EMP?

Faraday cages are the perfect protection from any type of EMP attack, or even a solar flare caused by the sun, and will be able to keep your essential electronic items safe. However, a few things you’ll need to remember is that the cage has to have no gaps or holes in it whatsoever, it must be grounded properly (usually by attaching the copper cable to the ground port), and all the sides must be equally protected. It needs to be waterproof and as thick as possible.

What are Faraday Cages Made From? 

Faraday cages can be made from any material that is able to conduct electricity, whether you use coils of wire, wire mesh, or metallic sheets. They can be made as small or as big as you’d like, whether it’s the size of a small shoebox or as big as an entire room. They also can range in all sorts of different shapes such as spheres, cylinders, and boxes. If you’re looking to create a makeshift Faraday cage for items such as your cell phone, simply wrap it in plastic and then surround the phone multiple times in aluminum foil. 

Are Faraday Cages Illegal?

No, as of right now, Faraday cages are not illegal. In fact, they are often used in government agencies and commercial factories as a way to protect their electronics from any type of external interference or damage. But keep in mind that in certain countries like the UK, they do prohibit individuals from blocking signals, and jamming up devices such as a cellphone. For now, you can protect yourself from Earth’s magnetic field. Scientist Michael Faraday is the guy responsible for the faraday cage.

How to Build a Faraday Cage

Are you feeling crafty and up to the task of making your own Faraday cage to protect all of your electronic devices? If so, all you’ll need is:

  • electrical tape
  • copper wire
  • wooden frame
  • aluminum or copper mesh

After you have all your materials gathered:

  1. Cut the mesh to fit the size of your frame
  2. Then tightly secure it with the electrical tape
  3. Lastly, wrap some copper wire around the entire contraption and connect it to the ground

One important last detail to remember: the thicker the shield is, the better chance it will have of surviving any type of electrical charge. And voila! You now have yourself an effective Faraday cage that should keep your electronic devices safe from an electromagnetic pulse attack.

Where You Can Find A Good Faraday Cage?

If you don’t feel confident in designing your own Faraday cage, there are still multiple places where you can find them. You can purchase them online, including Amazon and eBay, or in any electronics shop. Even Walmart is known to carry them. Furthermore, for those who are looking to buy one for their car, Faraday cages are often installed in the trunk of vehicles as a way to protect essential devices such as GPS and key fobs from an EMP attack.

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Where did the name Faraday cage come from?

They are named after Michael Faraday a scientist and inventor who developed the concept in the late 1830s. Faraday had read much of the electrical research performed by Benjamin Franklin. He built a room that was coated with metal foil to demonstrate that an excess charge on a charged conductor stayed on the outside of the enclosure and shielded the contents within it.

Franklin had performed an experiment where he lowered an uncharged cork ball attached to a silk thread into a metal can that was electrically charged. He noted that the cork ball wasn’t being charged with the electricity from the can even when he lowered it to the bottom of the can.

Are you safe within an airplane or your car if there happens to be an EMP?

Regarding aircraft, the FAA requires all aircraft to be able to take on an EMP with no loss or function to safety. That requirement means a lot to us as passengers! You hear about lightning strikes to commercial airliners and the plane survives due to the metal surface of the plane and its antenna acting as the electrical conductor needed to shield the contents of the plane, including people and equipment.

You know cars aren’t as safe since you can get electrical radio waves to the radio and cellular waves on your phone. Cars can shield some electrical and magnetic waves since they travel through the outside of the car and get grounded by the rubber tires on the ground.

That’s another reason you’re told to stay in your car if you think there may be high-voltage power lines and related wires that have come in contact with the car. Once linemen have moved or secured the power line away from the car you should be good. Let the trained electricians make sure you stay safe!

Remember that EM (electromagnetic) pulses can come from many sources. That’s why you’re told to get away from trees and out of higher open spaces and not use your golf clubs in case of an electric storm.

Just like with your car, it is good to ground your Faraday cage so the pulse has a way to exit (grounded) in case you happen to come in contact with the exterior shell or wall. If not grounded, when you touch that exterior YOU become the ground and the pulse passes through you which could prove fatal.

Is a Faraday cage illegal to build and or use personally?

As mentioned above, for personal use in most instances, you are fine to build or otherwise put a Faraday cage in use. There are countries like the UK where you can’t use a device to block signals. That means you couldn’t put into use anything that may interfere with signals from things like phones or possibly wi-fi that could interfere with Internet access. You might want to check with local regulations to make sure you aren’t doing something unique in its application to prompt concern.

I’m Personally Not Making or Purchasing A Faraday Cage

Here are my personal thoughts on Faraday Cages. I would have to store everything each day in one of these cages, boxes, or whatever. Or I could buy duplicate cell phones, laptops, computers, or anything I was worried about getting hit by an EMP. Well, I’m not going to do that. I’m more concerned with a complete power grid outage than an EMP. This is my personal opinion whether right or wrong.

Final Word

A Faraday Cage is an effective way for protecting your electronic devices from any type of EMP attack and other sources of radiation. Whether you choose to build one yourself or invest in a pre-made unit, having a Faraday cage can give you some much-needed peace of mind knowing that your electronics will stay safe during such attacks. What did you find interesting about Faraday cages, or is there any other valuable information on the subject that you’d be willing to share? I’d love to hear from you! May God Bless this world, Linda

Copyright Images: Trash Cans AdobeStock_145074835 By Rawf8

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  1. I worked in a secure environment in which we isolated phones in one for investigation purposes. It worked well.
    The trust issues I have with homemade or improvised faraday cages is that there is no real way to test them. My thought is that if a cell signal can get through then so can the EMP wave. That might be wrong but that’s all I have to go on. So stuffing it in microwave as many preppers will tell you doesn’t work. Put the phone or radio in and call it.
    That being said I have a metal box lined with cardboard etc that was built for me by a friend that I did store a radio and extra batteries, phone charger banks etc in. In fact I just finished recharging all them as we have an ice storm coming.
    Will it work? I dunno. There are too many variables like distance and strength to determine but I’ve done what I can. If nothing else I’ve got stuff where I can access it.

    1. HI Matt, this was probably the hardest post I have ever written because I don’t believe a homemade one I build will work. I don’t have enough confidence in my own abilities to build one like your friend built, a metal box, lined with cardboard. If an EMP hits, I’m assuming all of our power grids will be hit. My own opinion is I’m more worried about a cyber attack hitting our three vintage outdated power grids in the US. No power, no cell service, right? Hopefully, some ham radios will work, but will they? I’m with you there are too many variables like distance and strength. Linda

          1. Linda,
            Anything in a faraday cage cannot touch each other nor any part of the inside of the cage. Cage must be lined with cardboard and each item wrapped in a non-conductive material. Vehicles built before computers, only the altenator needs to be protcted.

          2. Hi Pam, great tips, this is why it doesn’t make sense to me to have one personally. I’m on my laptop 10-12 hours a day. I can’t see wrapping everything up, it’s just me. I trust your thoughts, thanks for sharing. Linda

          1. Too many factors to say. If it’s a large one in Kansas yeah most from coast to coast and northern Mexico to Canada.
            If it’s a small one in NYC then no I’ll still have power and signal probably.
            Is it an ICBM or a briefcase bomb? Is it a solar flare that hit up north?
            Lots of factors.
            No matter where the cell lines will clog way faster than the internet. We use it during tornados because the cell lines clog within minutes.

  2. I don’t store my everyday electronics in faraday cages, but I do store a lot of items in three separate galvanized steel trash cans that I use as faraday cages. Items inside are wrapped in paper, then aluminum foil, and the cans are lined with cardboard. Hopefully that’s enough, but as folks have mentioned, you can’t really be sure until an event and then it’s too late to do anything if your protection wasn’t sufficient.

    That said, here’s a short list of what I store:
    civil defense meters and dosimeters (along with dosimeter chargers)
    LED flashlights/lanterns
    radios and walkie talkies
    solar chargers for NiMH batteries (which I keep on a shelf since they have no electronics to damage)
    small foldable solar panel with some USB battery banks
    digital multimeters (to help trace trouble post event in damaged gear)

    Two cans are sealed with conductive tape to improve the shielding effect. The last can has items with battery packs that need to be topped up occasionally.

    Do I need all of this? Not really, I have candles and lanterns that don’t rely on electricity, and I’m old enough that any non-fatal dose of radiation probably won’t have time to cause cancer before I’d expire naturally. 😛

    But it could be very useful to have some of these items post event, and frankly I’d have them on a shelf for some disaster anyway so it cost me very little extra to get a few new trash cans and use some aluminum foil, craft paper and cardboard. So be thinking about what you’re storing and if it’s worth it to spend the time to store things in a cage that you don’t use regularly and might be useful in a post-EMP world.

    It’s really up to each individual how they want to spend their time and money on preparedness. Since I have my food and cooking supplies pretty well handled, I splurged a bit on things to make life easier if things go sideways. YMMV.

    Thanks for the thought provoking articles!

    1. Hi DMWalsh, as long as I can make bread, I can survive. Of course, I want a lot of lanterns, and flashlights, to name a few things. We will get through whatever comes our way. Linda

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