Wall wart is a slang term for certain types of power supply - typically those that are embedded in an over-sized AC plug. Other names include "power brick", "plug pack", "plug-in adapter", "adapter block", "domestic mains adapter", "power adapter", or AC adapter. These are typically packaged with electrical devices that do not contain their own power supply. This can be for reasons of size of the device, keeping a source of heat remote from the device, electrical noise isolation, making one device for international sale with a variety of power sources; and in the United States due to the economics of getting devices including an internal power supply certified by bodies such as the FCC.
These plugs have been criticised, hence the name wall wart. Problems with this type of power supply include:
Size - the power supply may obscure other power points; some power strips attempt to relieve this problem by varying the spacing between their sockets.
Weight - the weight of the power supply may pull it out of the power socket. This depends on the socket design of the country in question. Some power supplies are "power bricks" having a short AC cord so they can lie on the floor, thus relieving the strain at the expense of clutter. Some that hang on the wall are made long and thin, minimizing the leverage of their weight vector that pulls the plug out, at the expense of exacerbating the size problem.
Inefficiency - many wall warts have low efficiency, wasting electrical energy. Some use power even when the attached device is not in use or absent. (Since wasted electrical energy is released as heat energy, an inefficient power supply will feel warm to the touch, as will one that wastes power with nothing connected.) Switch-mode adapters, being more efficient, will not release noticeable heat even while being used.
Diversity - a lost or failed wart cannot immediately be replaced from the stock of a retail store, but must await delivery from the original equipment manufacturer if the item has not yet been discontinued. A wall wart made for other equipment may be electrically compatible but not mechnically in which case the plug won't fit or, worse, vice versa in which case the incompatibility may destroy the equipment or ignite a dangerous fire. A few warts have a transformer but not a rectifier, being intended to supply low-voltage alternating current to a device having its own rectifier, rather than direct current. This affords additional opportunities for misconnection, malfunction, destruction and combustion.
The problem of inefficiency of power supplies has become more well known, with George W. Bush referring to such devices as "Energy Vampires" . Legislation is being enacted in the EU and a number of states, including California, to reduce the level of waste caused by these devices. See standby power and the One Watt Initiative.
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