Book Excerpt: o a distance of severalhundred yards, and thus took an important step in the direction ofthe electric telegraph.It has since been found that FRICTIONAL ELECTRICITY APPEARS ONLYON THE EXTERNAL SURFACE OF CONDUCTORS.This is well shown by a device of Faraday resembling a smallbutterfly net insulated by a glass handle (fig. 5). If the net becharged it is found that the electrification is only outside, andif it be suddenly drawn outside in, as shown by the dotted line,the electrification is still found outside, proving that thecharge has shifted from the inner to the outer surface. In thesame way if a hollow conductor is charged with electricity, noneis discoverable in the interior. Moreover, its distribution on theexterior is influenced by the shape of the outer surface. On asphere or ball it is evenly distributed all round, but itaccumulates on sharp edges or corners, and most of all on points,from which it is easily discharged.A neutral body can, as we have seen (fig. 4), be charged byRead More
