Hello all, got a physics paper tomorrow and cant seem to answer the question that why do people use 110volt power supply in some countries and 220(or 240) volt power supply in others [img]redface.gif[/img]

Because the rotational shift of the Earth cause power fluxes from sun spots. The result is direct current infueses with the alternating current and frequency modulation, therby causing the voltage amperence difference on the ohms. Hope that helped [img]smile.gif[/img]

Just a comment, it probably won't answer your question. Just about every country I know of actually uses 220/240 as the "main" supply. Use both sides of the supply, and you have 220 for the dryer and stove, use only one side of the box (and neutral) and you get 110.

Countries that use 220 probably are trying to economize on infrastructure, or are fighting load problems. (Higher voltage means lower losses, and you don't need as thick a cable to carry an equivalent wattage)