power supply
The power supply unit converts AC (from a power point) to a low-voltage DC for the different parts of the computer. You can find the power supply in the motherboard of the computer. There is often a switch which can be used if you want high voltage or low voltage connection from the power point to the computer depending on what you want your computer to do.
References: http://en.wikipedia.org/wiki/Power_supply_unit_(computer)
http://pcsupport.about.com/od/componentprofiles/p/p_ps.htm
References: http://en.wikipedia.org/wiki/Power_supply_unit_(computer)
http://pcsupport.about.com/od/componentprofiles/p/p_ps.htm