What is a Faraday Cage?
Whether you’re a survivalist, or you’re just interested in physics, you might have already heard of a Faraday cage and what it does. However, not everyone knows of the potentially practical and even life-saving use of Faraday cages in day-to-day life.
Understanding the basic principles that allow these devices to work can help you better understand what their use might be and how they could apply to your life. Once you know that, you’ll find that building or buying one of them could prove useful whether you’re preparing for massive solar flares, an EMP attack, or just trying to prevent anyone from tracking your phone.
The Basics of the Science Involved
As you will see once you know what it is, building a Faraday cage or Faraday shield is definitely not rocket science. But what is it, and what does it really do?
The concept behind the cage is that of an area enclosed in conductive material. The conductive material is geared to capture any EM fields that stray towards it, regardless of whether a stronger electrical component or a strong magnetic component is present. Essentially, the cage works by blocking magnetic fields and directing electric current down into the ground and preventing it from reaching the objects (or subjects) inside of it.
The reason why this concept works in practice is because the electrical field hitting the shield from the outside causes the electrical charges within the cage to move in such an arrangement, that the electric impulse is steered away from the interior and discharged into the ground. The same scientific principle causes the Faraday shield to protect enclosed devices from radio frequency interference (RFI).
One of the best examples of a Faraday cage is your car. You might have heard the fact that you can’t get killed by lightning while sitting in your car, which is true because of the fact that cars are essentially Faraday cages, since the body acts as a conductive shield protecting you from the strong electrical energy in the lightning discharge.
Electrical signals are also blocked in a similar fashion, and the electronics inside Faraday cages are completely isolated from the conductive body. That way, any EM pulse that hits the box will never reach the electronics inside, so you can keep using them.
A Brief History of the Faraday Cage
The Faraday shield was initially designed in the 19th century based on the experiments of Michael Faraday, who observed that the electrical charge moving through a conductor resided only on its exterior, having little or no effect on the interior.
Faraday started experimenting with a high-voltage electrostatic generator that was used to discharge electric current onto the walls of a room coated in conductive metal. As the scientist noted, the electroscope he used to determine whether an electric charge was present on the inside of the room’s walls showed negative results.
Despite Faraday’s undeniable contributions, the effect that he used to create a Faraday shield was discovered even earlier.
Benjamin Franklin and Giovanni Battista Beccaria had both seen the effect in action long before Faraday, but were not able to reproduce it in controlled conditions.
Faraday shields are primarily designed to block or attenuate stable or gradually changing electromagnetic fields and pulses. They are not perfect, and given a pulse of a strong enough magnitude, they can be rendered useless. The best Faraday cage is the one that maximizes electromagnetic shielding, even if the effect isn’t completely foolproof.
Modern Day Applications of the Faraday Cage – Do They Always Work?
The Faraday cage is a device that has been known to work for a long time. As a result of its almost 200-year old heritage, the Faraday shield, as it’s also called, is being used today in a number of highly advanced applications, some of them present under our very noses in day-to-day life.
Whether you’re interested in building Faraday cages in your spare time or learning more about the physics and what makes them work, understanding what it takes to use a Faraday shield efficiently for your own unique purposes is what it’s all about. It’s important, however, to first take the time to learn more about the many applications Faraday cages can prove useful for.
The Most Prevalent Uses for Faraday Cages
There are a lot of potential uses for a Faraday cage, and some common, everyday items are actually Faraday cages. Let’s take a closer look at some of them below:
- Many of the electronics you might have around the house – especially those designed by some of the world’s leading manufacturers – feature advanced Faraday cages that are designed to block out radio frequencies and electromagnetic noise disturbances that could impair their proper functioning.
- Faraday cages shaped like wallets are available to help protect ATM cards, credit cards and driver’s licenses against radio frequencies and disturbances. They act as an important security measures to protect RFID chips against attacks. (Check out Faraday wallets
- MRI scan rooms are shielded against EM radiation and RFI to prevent any interference and ensure the success of the scanning process. They use advanced Faraday shield designs to achieve this feat.
- Microwave ovens are some of the best examples of using a Faraday shield. The cage, that you can actually see through the window of your microwave, acts exactly as a shield, blocking microwave radiation from escaping into the environment.
- Basically anything wrapped in multiple layers of aluminum foil can act as a Faraday cage. This applies to bags, pouches, backpacks and pocketed garments.
- Ever wonder how airplanes can fly through storm clouds without getting their pilots and passengers zapped by millions of volts of electricity? It’s because their cockpits and compartments are protected by metallic materials acting as Faraday shields. This is part of why it’s hard to get a clear signal with your cellphone from a plane flying at lower altitudes, even if you were allowed to do so.
- Many of the protective suits of men working in hazardous areas are Faraday cages. Electricians require them in particular, to prevent accidental injury or death while working with high voltages.
The Importance of Understanding the Limitations of a Faraday Cage
Despite the misconception that Faraday cages can offer full attenuation, this isn’t the case. A Faraday shield will completely block certain radio wave frequencies, however, depending on the amplitude, wave form and frequency of a wave, it might be only slightly attenuated or even not at all.
This is why it’s extremely important to use thicker Faraday shields and make sure the cage’s design fits the application you need it for. Also, when you use a Faraday cage for survival-related purposes, it’s vital to check the quality of the design, prior to considering its use.
Why Would You Need Faraday Protection Today?
The ingeniously simple design of the Faraday cage may have already saved your life countless times. Think of all the times you’ve flown or used your car in a thunderstorm, or even just used your microwave. The protective Faraday shield of your microwave oven or car can protect you from harmful radiation and even from lightning.
But what are the most common and important uses of a Faraday cage today? Also, what do you need to know about using a Faraday shield to prepare for possible natural disasters, a solar flare for example, or an EMP strike? We will investigate both of these concerns below.
The Most Common Choices for Protection
In this modern age, when technology is used to achieve just about everything we do, the use of a device that can shield electronic equipment from strong electric charges and EM fields can be extremely practical. This is where the Faraday cage comes in. But where exactly do we need EMP protection from a Faraday cage?
Most elevators are Faraday cages in and of themselves. Other rooms with metallic frames and walls can also simulate the Faraday shielding effect, and this can save your devices when you’re using them indoors during a storm.
Screened cables, such as USB cables and coaxial cables used for internet and cable TV are also protected using the same principles. You don’t have to worry about your TV or phone burning out if you have them plugged in and lightning hits your home.
A less common but extremely helpful use of Faraday protection is through Faraday bags. These special bags are used by forensic specialists to store electronic storage devices that could be wiped remotely by perpetrators to erase important evidence.
Boxes for Holding Tools and Essential Items
One of the most common use for Faraday cages in times when survival is of the essence – such as during natural catastrophes or an EMP attack – is their use as storage containers. While you can purchase Faraday cages for this purpose, you can also build your own for a relatively affordable price, depending on the thickness of the box and the materials you’d like to use.
The boxes can primarily be used to store backup electronics such as radios, cell phones and mobile devices, laptops and even flashlights – as some flashlights come with chips that could be damaged by an EMP. These devices can prove extremely useful to provide you with a means of communication or information when your main computer and TV set are down.
Rechargeable hand tools such as saws and drills, as well as small electric motors that could potentially be used as electricity generators when the power is off will also have to be stored in Faraday shielded boxes or cages. It’s also a good idea to store batteries and solar panels in shielded rooms and boxes, so that they won’t be damaged.
As you can see, there are plenty of uses for this remarkably helpful type of box. The Faraday cage is more helpful than ever now that shielding electronics and electrical equipment has even become a daily struggle for some.
How to Build a Faraday Cage
The Importance of EMP Protection
When it comes to using Faraday cages, a lot of people don’t see the point. After all, there are easier ways to protect against lightning, and most modern devices such as cellphones are provided with built-in protection against radio frequency interference.
However, since the discovery of EMP in 1962, there has been growing interest in the protection against EMP weapons and powerful bombs that could also create electromagnetic pulses strong enough to knock out most electronics in a larger area.
There are books and sources that can tell you precisely what would happen in the case of an EMP attack, and the picture they paint isn’t pretty. Basically, all you have to do is imagine that your entire city or area was stripped of technology, and not even the cars work anymore. Aside from mass panic, there would be theft, riots and people trying to profit from the mayhem. As a result, keeping a stash of electronic devices, tools, batteries and electronic components safety stashed away in Faraday boxes can be extremely useful in such a situation.
Types of Faraday Cages You Can Build
Building a Faraday cage isn’t rocket science. You can do it simply by lining a cardboard box with some heavy-duty aluminum foil. You can then test whether the box works by placing your phone or a small AM radio inside. If the box is not 100% covered in aluminum foil, then the shielding will be incomplete, and your phone will ring, or the radio will keep working.
One of the simplest Faraday cages you can build is from a common ammo can bought at your local army surplus store. An ammo can is already like a Faraday cage, since it’s made of metal and features internal padding. While small, it can work quite well for tiny electronics.
A bird cage, a trash can and a metal storage cabinet can all be used as effective Faraday cages that can at least attenuate an EMP, in case it hits. You can add additional layers of aluminum foil, for example to cover any gaps in order to ensure that 100% of the surface will be protected.
Using Aluminum Foil to Protect Storage Containers
To build a working Faraday cage, you will need supplies such as heavy-duty aluminum foil, plastic wrap, old clothes and fabrics for wrapping items, cardboard boxes of various sizes – depending on your needs – and all the small tools, devices and electrical components that could be affected by an EMP.
The process is quite simple, and it won’t take much time. You just have to wrap the items you want to protect in cloth, and then place them inside the cardboard boxes. You can then proceed to gently wrap the boxes in plastic wrap, and then in at least three layers of aluminum foil for adequate protection. You can also opt to wrap the boxes before placing the items inside, and then use two additional layers of aluminum foil to make sure they are adequately protected.