My specific question is "How is electrical energy made available to devices?" Everyone knows that "devices transfer electrical energy into useful forms" of energy, such as light and heat. What I have discovered is that no source I have found has been able to describe exactly how devices GET that electrical energy. I understand potential differences, voltages, current, power, and almost anything else about electrical circuits, but what I cannot find, even in my "Physics for Scientists and Engineers" nor any of my Freshman Engineering texts is how these devices get energy. So my question stands, slightly modified, as: "How does an electrical current enable the transfer of electrical energy to devices?" Thank you.