▁devices ▁ ▁A ▁fifth ▁case , ▁histor ically ▁significant , ▁is ▁that ▁of ▁electro des ▁that ▁completely ▁enc lose ▁the ▁volume ▁ ▁of ▁the ▁device , ▁i . e . ▁ ▁. ▁Indeed , ▁choosing ▁again ▁the ▁Dir ich let ▁boundary ▁conditions ▁of ▁▁ ▁on ▁ ▁and ▁ ▁on ▁the ▁other ▁electro des , ▁from ▁the ▁equations ▁for ▁the ▁open ▁device ▁we ▁get ▁the ▁relationships ▁▁ ▁, ▁ ▁with ▁▁ ▁, ▁ ▁thus ▁obtain ing ▁the ▁Ram o - S ho ck ly ▁theorem ▁as ▁a ▁particular ▁application ▁of ▁the ▁electro kin emat ics ▁theorem , ▁extended ▁from ▁the ▁vac u um ▁devices ▁to ▁any ▁elect rical ▁component ▁and ▁material . ▁ ▁As ▁the ▁above ▁relationships ▁hold ▁true ▁also ▁when ▁ ▁depends ▁on ▁time , ▁we ▁can ▁have ▁a ▁si xty ▁application ▁if ▁we ▁select ▁as ▁ ▁the ▁electric ▁field ▁generated ▁by ▁the ▁electro de ▁volt ages ▁when ▁there ▁is ▁no ▁charge ▁in ▁. ▁Indeed , ▁as ▁the ▁first ▁equation ▁can ▁be ▁written ▁in ▁the ▁form ▁▁ ▁, ▁ ▁from ▁which ▁we ▁have ▁ ▁, ▁ ▁where ▁ ▁corresponds ▁to ▁the ▁power ▁entering ▁the ▁device ▁ ▁across ▁the ▁electro des ▁( en clos ing ▁it ). ▁On ▁the ▁other ▁side ▁▁ ▁, ▁ ▁gives ▁the ▁increment ▁of ▁the ▁internal ▁energy ▁ ▁in ▁ ▁in ▁a ▁unit ▁of ▁time , ▁ ▁being ▁the ▁total ▁electric ▁field ▁of ▁which ▁ ▁is ▁due ▁the ▁electro des ▁and ▁ ▁is ▁due ▁to ▁the ▁whole ▁charge ▁density ▁in ▁ ▁with ▁ ▁over ▁S . ▁Then ▁it ▁is ▁,