The power supply is one of the more important components in the system unit. It coverts AC electricity from your outlet into lower voltage DC electricity that your PC can use.

The electricity the power supply provides is measured in watts. Power supplies range from 100-250 watts. Newer PCs generally use a 200 watt power supply. The more watts a power supply produces, the more peripheral devices it can support.

The power supply also contains a built in cooling fan. This circulates air within the system unit to keep the electronic components cool. This is the noise you hear when you turn on your PC.