Most parts of the world have standardized their electricity supply systems to either 60 hertz (U.S. and most of the Americas) or 50 hertz (Europe and most of Asia). This refers to the number of times per second that alternating current reverses direction.
Simple adaptors that travelers carry deal adequately with the difference in voltage but do not convert the frequency. Consumers should look for one that is rated for 110 to 220 volts and 50/60 hertz. They should also be aware, though, that electrical devices with motors turn 17 percent slower. The power goes down by 17 percent, and more problematic, mechanical cooling is less, such that appliances built for 60 hertz tend to burn out sooner when operated at 50 hertz.