Alternating current (AC) adapters are used to power or charge many common electronic devices, such as mobile phones, laptop computers, or external hard drives. An AC adapter changes AC power from an electrical outlet into the type of power or voltage that an electronic device needs to work. Typically, each device has a designated adapter that is pre-set to the proper voltage conversion. For this reason, among others, adapters generally are not interchangeable.
If a device does not have its own supply of power, it likely has to use an AC adapter in order to get power from the electricity mains of a building. An adapter is a type of power supply — a device that provides power to another device — and is used with cell phone chargers or the power cords for gaming systems, for instance. The large block that plugs into the wall is the power supply that converts AC power to the appropriate form for the device. Other names for this type of adapter include a plug pack or a wall wart.
Another place one may find a power supply is in a laptop charger or the power cord for a printer. In order to keep the power supply from taking up space on a wall and blocking other outlets, some AC adapters have their power supplies in a "brick" that lies on the floor. This brick-in-line configuration allows for the actual plug to be a normal size to allow more room at the wall outlet. These adapters often have nicknames, such as power bricks.
Having an adapter to power a device allows for several advantages to the device and its manufacturer. For example, heat and electronic interference are kept away from the device that is being powered. The device can also get the power it needs without having to generate its own electricity. In addition, the manufacturer can market the product throughout the world since all he needs to do is include or sell the correct adapter for the country in which the device is being sold or used.
One of the drawbacks to an AC adapter is that they oftentimes can be difficult to replace. If the adapter from a laptop is misplaced, for instance, an adapter from another type of laptop generally cannot be used to replace it. To offset this difficulty, some manufacturers have developed universal adapters. They come with a switch so a person can choose the appropriate voltage as well as interchangeable tips so he can choose the correct one for his device.