Editing Faraday cage (section)

==== 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.