Electricity & Megnetism

Faraday’s Cage

The Faraday cage prevents the entry of electric and magnetic fields from conductive structures, an effect known as electrostatic shielding.

The Faraday cage is a system that prevents the passage of electric and magnetic fields. [1]
The Faraday Cage was an experiment performed by physicist Michael Faraday that showed the effect of electrostatic shielding. By involving conductive materials (which are easily traversed by electrons), it is possible to create a barrier against electric and magnetic fields.

With electrostatic shielding , it is possible to protect electronic devices against external interference, the most common examples of using this mechanism being voltage sources, lightning rods and microwave ovens.


  • The Faraday Cage is a physical experiment that explains electrostatic shielding.
  • Electrostatic shielding is a physical phenomenon that bars electric and magnetic fields.
  • The physicist Michael Faraday developed this experiment in 1836.
  • The most practical examples of using this effect are voltage sources, microwaves and lightning rods.

What is a Faraday Cage?

The Faraday cage is an experiment made by the English physicist Michael Faraday , in 1836, and consists of using a conductor (a material that has the ability to conduct heat and electricity) to shield its interior from electric and magnetic fields .

Representation of a Faraday cage

This effect occurs due to the distribution of charges on the conductive surface, making the surface equipotential (surface where all points have the same electrical potential) and its interior without electrical potential or with zero potential.

After all, what is the Faraday cage for?

Michael Faraday discovered that by applying an electric field to a conducting structure, that structure produces electric charges opposite the electric field, and one cancels the other, preventing the electric field from entering the interior of the surface.

Because of these characteristics, the Faraday cage is a great protection against unwanted electric and magnetic fields in the system , as it creates an isolation barrier in devices.

Representation of electrostatic shielding and isolation provided by a Faraday cage.

Thus, electrostatic shielding does not allow electromagnetic waves , electric or magnetic fields to interfere with electronic equipment.

How is a Faraday cage made?

To build a Faraday cage, you need a conductive structure, like a metal, wrapped around the object you want to insulate.

A simple example is putting aluminum foil around your cell phone. You will notice that the device will not be able to receive calls.

What are the Faraday cage applications?

Normally, the Faraday cage is used to coat equipment that is sensitive to electric and magnetic fields , such as voltage and microwave sources, and it can also be used as a lightning rod .

In voltage sources, electrostatic shielding is necessary to prevent overloading and damage to equipment. The lightning rod works on the same principle. Grounded to the ground, it blocks the passage of fields and carries extra voltage to the ground.

The microwave, on the other hand, works in a different way, as it prevents the output of fields, more specifically electromagnetic waves (microwaves). Because of this, we can ensure that the electromagnetic waves emitted by a microwave do not affect human health or surrounding equipment.

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