What frequency does the rest of the world use?

• A. 50 hertz
• B. 60 hertz
• C. 120 hertz
• D. 200 hertz

Answer: (A)

Electrical grids run at a fixed frequency, which is how fast the current alternates each second. Most countries use 50 hertz, a standard that formed early in the spread of AC power and became a global convention, allowing equipment and utilities to be built to the same specifications and work together smoothly. A different standard—60 hertz—is used primarily in North America due to historical choices about early equipment and grid development, and that difference remains today. Frequencies higher than these, like 120 hertz or 200 hertz, aren’t used as mains frequencies because they would require much larger, heavier, and more expensive transformers and motors for long-distance power delivery. You’ll encounter 120 hertz as the ripple frequency in rectified power coming from a 60 hertz supply (and 100 hertz ripple from a 50 hertz supply), but those higher numbers are not used for the actual grid frequency.