Electrons can be "ripped" away from their atom with the application of energy in one of many forms. One method that was common in every home for years, was in vacuum tubes. Also called electronic valves in some countries. Also, in CRT's, like television picture tubes. In this application, heat was applied to a little piece of tungsten, containing a bit of thorium. Electrons jump off of their atoms, many into the vacuum in the tube, where they are used to amplify signals, or used to bombard the phosphorus screen on a television tube, forming the TV image.