AC v. DC
Friday, November 13, 2009 In a direct current (DC) circuit, electrons move in the same direction through the circuit at all times; this is the type of current provided by batteries and solar cells. DC is used to power most electronics, which run on relatively low voltages. Thomas Edison initially backed DC power distribution.
In an alternating current, or AC circuit, the direction of electrical flow periodically changes direction. The AC from a wall socket typically does so at a frequency of 50 to 60 Hz. Nikola Tesla and George Westinghouse favored high voltage AC systems and transformers, which allowed for better transmission efficiency over greater distances, using fewer and smaller wires than Edison’s competing DC system would have required.
The obsolete term AC/DC was used to describe older equipment that could run on either mains AC or DC when both means of power distribution were available.