Now, this supply of electricity is not arbitrary but follows a predetermined sequence. This is called Frequency. That is the rate at which it goes between achieving the upper and low flow of electrons in both direction; positively and negatively.
Frequency is measured in Hertz and short form is Hz. UK/Nigeria's frequency is 50Hz and USA/Japan is 60Hz.
For most domestic equipment, once you use a step down transformer for any equipment from USA you will be fine.
However, most industrial equipment needs other Frequency converter, to work normally.
AC supply is used to transmit power over long distances because of low losses over a very long distance; which means you get about the same Power at the beginning and end of the line.
Also, it is generally cheaper to construct AC than DC line.
However, with improvement in appropriate technologies, DC transmission lines are springing up in various parts of the world especially China & USA.
© Tunde Y. Salihu, 2016