Faraday's Cage: how it works, applications

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cage offaraday is the name given to a casing that is made of material conductor and used to shield your interior from interference andexternal electromagnetic. It emerged as a scientific experiment, developed by the English physicist Michael Faraday in the year 1836, and is still used today to protect electric circuits sensitive to the incidence of electromagnetic waves of different frequencies.

See too: Michael Faraday – discoveries and scientific legacy

How Faraday's Cage Works

Faraday's cage is nothing but a technological application of a phenomenon known as electrostatic shield. This phenomenon only happens in conductive materials (metals), such as iron, silver and copper, which are characterized by having a large number of free electrons, able to move freely along the conductor.

Due to the high mobility they have, the electrical charges of conductive materials prefer to spread across the surface of metals. Imagine the case where a large number of electrons are placed in the center of a conductor: the repulsion between them would cause them to quickly move as far away from the center as possible. Once distributed, the loads make the entire surface of the conductor have the same value of

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Electric tension, giving rise to a surface equipotential.

The conductive mesh that surrounds the person protects him, functioning as a Faraday cage.
The conductive mesh that surrounds the person protects him, functioning as a Faraday cage.

Since, in conductors, all the loads are distributed on its surface, O electric field inside it becomes null and as a consequence, there is no electrical potential difference inside these materials. Such behavior ensures that any body left inside a closed conductor will be free from the influence of external electric fields, however intense.

When an external electric field is directed into a Faraday cage, the cage's electrons rearrange so that the electric field inside the cage remains null. In this way, with these devices, it is possible to prevent the occurrence of an electrical discharge or even the incidence of an electromagnetic wave.

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The same happens with the incidence of electromagnetic waves. In this case, the spacing between the "holes" of the cage must have dimensions close to the length of the electromagnetic wave that you want to bar.

See too: Curiosities about rays that make anyone's hair stand on end

Faraday Cage Applications

There are a large number of technological applications that make use of the principle used in Faraday's cage. These devices are often sensitive to electrical fields and magnetic fields and, therefore, they are coated with metal plates or meshes.

Check out some examples of devices that make use of a Faraday cage in order to function correctly:

  • hard drives (HD);

  • voltage sources;

  • Faraday's lightning rod;

  • protective clothing;

  • microwave.

Just as the Faraday cage can be used to block interference from entering, it can also be used to block the output of electromagnetic waves, as in the case of microwave. In addition, vehicles such as cars and aircraft also function as Faraday cages, protecting passengers inside from electrical discharges coming from outside.

By Rafael Hellerbrock
Physics teacher

Would you like to reference this text in a school or academic work? Look:

HELERBROCK, Rafael. "Faraday's Cage"; Brazil School. Available in: https://brasilescola.uol.com.br/fisica/gaiola-de-faraday.htm. Accessed on June 27, 2021.


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