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Faraday Cage: Shielding of Electric Fields

A Faraday cage, named after the British physicist Michael Faraday, is a metallic cage that shields an external electric field \( \class{purple}{E} \). This electrically conductive Faraday cage is used, for example, to protect electronic devices from electromagnetic interference and damge.

A conductive hollow box is located in an external electric field \( \class{purple}{E} \).

The electric field inside the cage is neutralized by the electric field of the charges in the conductor.

As the cage is conductive, the electrons can move freely on its surface. In an electric field, they move against the direction of the external field. These electrons are missing on the other side of the box, which is why this side is positively charged.

Due to this charge separation, a further electric field is created in the box, which is of the same magnitude as the external field and the two fields point in opposite directions. They cancel each other out inside the cage. The inside of the cage is therefore field-free. We say: The box acts as a Faraday cage.