When a computer user unpacks a notebook computer, one of the first components he will see is the power brick. This large, rectangular piece weighs a pound or two, but is essential to the machine's operation.

The power brick is part of the external power supply. It also provides the power for the computer to charge its batteries. Plugging straight AC from a wall outlet into a notebook would blow the circuits, so lower-voltage DC powers the notebook. The power brick accomplishes the conversion. The computer is plugged into the power brick, while a cord runs from the power brick into a standard AC plug.

A power brick will usually have a light on it to alert the user that it is functioning properly. If a notebook computer will not recharge its batteries, then the power brick may be at fault. However, power bricks are manufactured by the computer companies themselves, and what runs one notebook may not power another. A user will have to look for a power brick that is designed for his particular computer model.

Since power bricks are so heavy and bulky, they should lie flat at all times. The weight of the power brick, if suspended, could pull the outlet from the computer, damaging both the notebook and the brick.

The power brick will also become warm when it is used, so it should rest on a non-flammable surface. It should be placed on a desk or on the floor, not on a rug or blanket. A user should never try to open or repair the power brick, a task best left to professionals. The power brick should also be protected from being dropped and from spills, as with any electrical device.

Most computer supply stores and Web sites stock power bricks, so if a user needs one, they are readily available. Depending on the computer model, power bricks are priced from US$30 or so to over US$100. Comparison shopping is a must. Some stores will have differences of up to US$20 or US$25, depending on the brand. It will always benefit the computer owner to check out several Web sites and call local stores to get the best price.