AC, dc, or both? [Essay]

Unless you are an engineer—more specifically, a power engineer—it is doubtful that you have ever given a single thought to what is behind the switch whenever you turn on lights, televisions, radios, or other electrical devices. The normal expectation is that, when the switch is thrown, the lights come on—each and every time. Outstanding availability and reliability are expected of the system. Other than a couple of wires running from a telephone pole to the house or, perhaps, an underground cable from a box at the side of the street, just what is the power grid, and what is its history?