He discovered that when an electrical conductor becomes charged, all the additional charge is on the outside of the conductor. This means that the surcharge does not appear inside a room or metal cage. An external electric field leads to the reorganization of the charges and this cancels the internal field. Electric fields create forces on the electrons in the conductor, creating a current, which will aid reorganization. Faraday noticed that the conductor's charge did not affect anything inside it. He even went so far as to build a room lined with sheet metal and used an electrostatic generator to create a high voltage discharge that hit the outside of his room lined with sheet metal. Michael found no electrical charge on the interior walls and used an electroscope to prove it