To power your computer sufficiently, you need a Computer Power Cord designed for AC125V use. Electrical cables made for 5-15P to C-13 work very well when it comes to powering CPUs and other high-voltage electronics.
Built as a 18AWG/3, the cord isn't very thick, but is strong enough that it won't break easily. These computer power cords are available in various lengths, from 1.5-12ft.