Electrostatic shielding is the phenomenon that is observed when a Faraday cage operates to block the effects of an electric field. Such a cage can block the effects of an external field on its internal contents, or the effects of an internal field on the outside environment.
A Faraday cage is a closed chamber consisting of a conducting material or a mesh of such a material. This type of cage was first invented by Michael Faraday in 1836, and can block external static and non-static electric fields.
When an external electric field operates on a Faraday cage, the charges within the cage (which are mobile, as the cage is a conductor) rearrange themselves to directly counteract the field and thus "shield" the interior of the cage from the external field (Figure 1)
The action of a Faraday cage may depend on whether or not it is grounded. Consider a charge placed within a cage. If the cage is not grounded, electrons in the cage will redistribute such that the interior wall of the cage takes on a charge opposite the internal charge. This would leave an exterior wall of opposite charge to that of the interior. If it is grounded, however, excess charges on the exterior of the cage will go to the ground, leaving the exterior wall of neutral charge.
Faraday cages are limited in their effectiveness, and cannot block static and slowly varying magnetic fields, such as that of the planet Earth. They can, however, shield the interior from external magnetic radiation provided that the mesh is smaller than the wavelength of the radiation and that the shield is sufficiently thick.
Microwave ovens contain energy within themselves, shielding the outside from harmful radiation.
Electrical linemen often wear suits made of Faraday cages so as to avoid electrocution.
Elevators can act as unintended Faraday cages, shielding cell phones and radios from signal from the outside.