What is a Faraday cage?


A Faraday cage is a protective enclosure that prevents certain types of electromagnetic radiation to enter or exit, depending on Florida State University Magnetic Field Laboratory. First invented in the 19th century, the cage has a number of practical uses – and a few fun applications, too.

We use Faraday cages quite regularly in places like hospitals and even your kitchen. Some Faraday cages are better than others, but they all follow the same principles.

Here’s what exactly a Faraday cage is, how it works, and how we use it in everyday life.

Related: Who invented the electric bulb?

How does a Faraday cage work?

A Faraday cage is basically a container, or shield, that blocks electromagnetic radiation from across the entire electromagnetic spectrum, such as radio waves and microwave, according to Florida State University.

It works on the principle that when an electromagnetic field hits something that can conduct electricity, the charges stay outside the conductor rather than travel inside.

In more practical terms, this means that a cage made of a material that can conduct electricity will prevent the passage of certain electromagnetic radiation. This applies to both constants or static, electric fields and electric fields changing or not static.

Who invented the Faraday cage?

Michael Faraday invented the faraday cage in 1836. (Image credit: Getty Images)

British scientist Michael Faraday – who is also known for Faraday’s Law of Induction – invented the Faraday cage in the 19th century, building on the work of American scientist Benjamin Franklin in the previous century.

According to National archives.

Later, in January 1836, Faraday moved into the theater of the Royal Institution in London, where he worked in the basement, reports The Guardian. Inside the theater, he built a 12-foot cube with a wooden frame on four glass supports. He covered the paper walls of the cube with a sheet of metal. And then, apparently, he went inside, used an electrostatic generator to detonate the room with electricity, and almost lived there for two days. Inside the box, Faraday discovered what he suspected all along – that electricity is a force, not a material liquid that flows through wires like water through a pipe, as thought at the time, reported the Royal Institution.

Inside the “cage”, Faraday’s electroscope detected no electricity; only the metal foil surrounding the coin conducted electricity, showing the concept of a Faraday cage, according to Florida State University.

What are Faraday cages made of?

A Faraday cage can be made of any material that can conduct electricity. This could be wire mesh, metal sheets, or spools of wire.

They can be any shape, such as a box, sphere, or cylinder, and any size, from extremely small to extremely large. Something as simple as aluminum aluminum foil can provide the exterior of the cage, according to Florida State University.

The outer, or conductive, coating can be extremely thin, like a sheet, but making it thicker will provide additional protection against stronger electric fields.

What are some examples of Faraday cages?

Faraday cages can be somewhat complex or extremely simple; they can range from the size of a shoebox to an entire building. Wrap your phone in plastic, then wrap it in foil, for example, and it’s a makeshift Faraday cage.

If you have a microwave in your kitchen, this in itself is a form of a Faraday cage, keeping microwaves trapped inside the machine so that they reheat your food and don’t leak out, according to the newspaper. Physics education.

On a larger scale, Magnetic resonance imaging Scanners (MRIs) in medical settings use Faraday cages to prevent radio signals from entering the room and interfering with equipment, which is, according to the manufacturers of MRI scanners. PEE.

Is a car a Faraday cage?

Kind of. If lightning struck your car, the exterior of the car would likely protect you from the electrical charges involved, as its exterior can conduct electricity.

The car’s rubber tires allow lightning electricity to pass through the ground, removing the charge from the car, according to Encyclopedia Britannica.

Cars, however, are not perfect examples of Faraday cages. If you touch a metal connected to the exterior of the car when lightning strikes, the results could be extremely dangerous. You can also still receive a signal on your phone when you are inside a car, for example, which means that some electromagnetic radiation can enter and exit.

A Faraday cage could protect against a lightning strike, or something even worse, like an EMP or a solar flare. (Image credit: Getty Images)

Does a Faraday cage need to be earthed?

Grounding a Faraday cage – that is, providing a means for the electrical charge from its exterior to the outlet – is important in terms of safety, but it is not necessary that a Faraday’s cage works.

Without grounding, the electrical charge will remain outside of a Faraday cage. If you touch it, it could let the charge pass through you which would be very dangerous.

Grounding the cage allows the load to exit. It could be in the form of a wire to remove the load, or something as simple as the tires of a car connected to the road.

Are Faraday Cages Illegal?

Not really. For the most part, they are good and they can be seen used in a variety of different settings, as we explained earlier.

However, some countries like the UK prohibit the use of jamming devices to block signals, such as from a telephone. Although Faraday’s cages are technically legal, their use in such a scenario could be questionable, according to the UK Communications Office (Ofcom).

In 2016, for example, a bar in the UK used a Faraday cage to block cell phone signals to prevent patrons from looking at their phones; they created Faraday’s cage by installing copper wire mesh in the bar’s ceiling and metal foil in the walls, NPR reported.

Are Faraday cages blocking Wi-Fi?

Yes, if you surround your Internet router with a Faraday cage, it will no longer be able to transmit electromagnetic radiation outside, blocking your access to the Internet, according to Popular mechanics.

While it can be an interesting experience, there’s no practical reason for wanting to do it – unless, like a certain bar, you just want people in your house to stop using their phones.

Related: 5G network: how does it work, and is it dangerous?

Would a Faraday cage protect from an EMP?

An electromagnetic pulse (EMP) is a weapon designed to neutralize electronic equipment by using a strong electric field to create short circuits in such equipment, according to the Washington State Department of Health.

A Faraday cage would be able to prevent such an attack. However, given the strength of the electric field involved in an EMP, such a cage should be as tight as possible with thick, conductive sides and no holes that can leave a charge inside.

While EMPs can be the result of weapons, natural events such as solar flares from our sun can also generate them, making Faraday cages a potentially useful tool in protecting us from such events.

Additional resources


Comments are closed.