Editing Faraday cage (section)

=== Continuous ===
A continuous Faraday shield is a hollow conductor. Externally or internally applied electromagnetic fields produce forces on the [[charge carrier]]s (usually electrons) within the conductor; the charges are redistributed accordingly due to [[electrostatic induction]]. The redistributed charges greatly reduce the voltage within the surface, to an extent depending on the capacitance; however, full cancellation does not occur.<ref>{{cite journal|url=https://people.maths.ox.ac.uk/trefethen/chapman_hewett_trefethen.pdf |doi=10.1137/140984452|title=Mathematics of the Faraday Cage |year=2015 |last1=Chapman |first1=S. Jonathan |last2=Hewett |first2=David P. |last3=Trefethen |first3=Lloyd N. |journal=SIAM Review |volume=57 |issue=3 |pages=398–417 }}</ref>

==== Interior charges ====
If charge <math>+Q</math> is placed inside an ungrounded Faraday shield without touching the walls, the internal face of the shield becomes charged with <math>-Q</math>, leading to field lines originating at the charge and extending to charges inside the inner surface of the metal. The field line paths in this inside space (to the endpoint negative charges) are dependent on the shape of the inner containment walls. Simultaneously <math>+Q</math> accumulates on the outer face of the shield. The spread of charges on the outer face is not affected by the position of the internal charge inside the enclosure, but rather determined by the shape of outer face. So for all intents and purposes, the Faraday shield generates the same static electric field on the outside that it would generate if the metal were simply charged with <math>+Q</math>. See [[Faraday's ice pail experiment]], for example, for more details on electric field lines and the decoupling of the outside from the inside. Note that electromagnetic waves are not static charges.

If the cage is [[ground (electricity)|grounded]], the excess charges will be neutralized as the ground connection creates an [[Electrical bonding|equipotential bonding]] between the outside of the cage and the environment, so there is no voltage between them and therefore also no field. The inner face and the inner charge will remain the same so the field is kept inside.

==== Exterior fields ====
[[File:Skin depth by Zureks-en.svg|thumb|350px|Skin depth vs. frequency for some materials at room temperature, red vertical line denotes 50-Hz frequency:{{ubl
|Mn–Zn – magnetically soft [[Ferrite (magnet)|ferrite]]
|Al – metallic [[aluminum]]
|Cu – metallic [[copper]]
|steel 410 – magnetic [[stainless steel]]
|Fe–Si – [[grain-oriented electrical steel]]
|Fe–Ni – high-permeability [[permalloy]] (80%Ni–20%Fe)
}}
]]

Effectiveness of  the shielding of a static electric field is largely independent of the geometry of the conductive material; however, the static magnetic fields can penetrate the shield completely.

In the case of varying electromagnetic fields, the faster the variations are (i.e., the higher the frequencies), the better the material resists magnetic field penetration. In this case the shielding also depends on the [[electrical conductivity]], the magnetic properties of the conductive materials used in the cages, as well as their thicknesses.

A good example of the effectiveness of a Faraday shield can be obtained from considerations of [[skin depth]]. With skin depth, the current flowing is mostly in the surface, and decays exponentially with depth through the material. Because a Faraday shield has finite thickness, this determines how well the shield works; a thicker shield can attenuate electromagnetic fields better, and to a lower frequency.