The power supply provides the necessary electrical power to make the computer operate.
The power supply takes standard 110-volt AC power and converts it into 12 volts, 5 volts and sometimes 3.3-volt DC power.
Power supplies, often referred to as "switching power supplies", use switcher technology to convert the AC input to lower DC voltages.
A vast majority of the power supplies is about the size of a shoebox cut to half and are usually gray or metallic. Leading out of the power supply are a number of connectors. There is one set of connectors for the motherboard, and there are number of other connectors for other components.
On most computers, the back of the power supply is visible, with a connection for the power plug. There is always a fan that keeps the interiors of the PC cool.
