What is AC/DC?

When Thomas Edison and his crew invented a reliable electric light bulb, he followed it up by developing the power systems to run it, rightfully envisioning a future world full of light bulbs. (We usually refer to these as “light bulbs,” but “lamps” actually is the correct term. Bulbs are for planting.) Edison employed direct current (DC), which now is used in battery-operated gadgets in which the current flows from the negative terminal of the battery to the positive terminal. A battery is basically a container of chemicals whose electrochemical reactions produce excess electrons. Our electrical systems use alternating current (AC), which was developed by Edison’s contemporary, George Westinghouse, after he bought up patents from Nikola Tesla and William Stanley. Once again, someone with business sense trumped the scientific minds possessing the money-making ideas. It took Edison, the lampmeister, a few years to go along with this AC business, but he eventually told Westinghouse’s son to let his dad know he was right.
A direct current just means that the electric current flows continuously in one direction and keeps going until it finds something to run such as a radio or a light bulb. An alternating current flows in one direction—say, to a receptacle—and then flows back in the opposite direction. You might be thinking, so what? When was the last time alternating current was discussed on late-night talk shows? Probably never. Alternating current, however, does have some useful, consumer-friendly features such as the following:

• Through a series of transformers, an AC can be increased or decreased in value. (The current can be made stronger or weaker.) This means that, instead of a zillion watts of power heading for your panel box, you’ll get a reduced amount that you actually can use.
• Alternating current is efficiently transported over long-distance power lines.
• It’s easy to convert from AC to DC, but it’s expensive to go from DC to AC.