Mains plug

AC power plugs and sockets are devices that allow electrically operated equipment to be connected to the primary alternating current (AC) power supply in a building. Electrical plugs and sockets differ in voltage and current rating, shape, size and type of connectors. The types used in each country are set by national standards, some of which are listed in the IEC technical report TR 60083, Plugs and socket-outlets for domestic and similar general use standardized in member countries of IEC. The scope of IEC TR 60083 states: "The report only contains systems for which standard sheets have been published in a National Standard, which may be a National Standard of the country itself or any other IEC member country".

Plugs and sockets for portable appliances started becoming available in the 1880s, to replace connections to light sockets with easier to use wall-mounted outlets. A proliferation of types developed to address the issues of convenience and protection from electric shock. Today there are approximately 20 types in common use around the world, and many obsolete socket types are still found in older buildings. Co-ordination of technical standards has allowed some types of plugs to be used over wide regions to facilitate trade in electrical appliances, and for the convenience of travellers and consumers of imported electrical goods. Some multi-standard sockets allow use of several different types of plugs; improvised or unapproved adaptors between incompatible sockets and plugs may not provide the full safety and performance of an approved socket and plug combination.

The International Electrotechnical Commission publishes IEC 60050, the International Electrotechnical Vocabulary, which is also available as IEV Online.

Generally the plug is the movable connector attached to an electrically operated device's mains cable, and the socket is fixed on equipment or a building structure and connected to an energised electrical circuit. The plug has protruding pins or, in US terminology, blades (referred to as male) that fit into matching slots or holes (called female) in the sockets. A plug is defined in IEC 60050 as an accessory having pins designed to engage with the contacts of a socket-outlet, also incorporating means for the electrical connection and mechanical retention of flexible cables or cords; a plug does not contain components which modify the electrical output from the electrical input (except where a switch or fuse is provided as a means of disconnecting the output from input). There is an erroneous tendency to refer to power conversion devices with incorporated plug pins as plugs, but IEC 60050 refers to these as 'direct plug-in equipment', defined as equipment in which the mains plug forms an integral part of the equipment enclosure so that the equipment is supported by the mains socket-outlet. In this article, the term 'plug' is used in the sense defined by IEC 60050. Sockets are designed to prevent exposure of bare energised contacts. Sockets may also have protruding exposed contacts, but these are used exclusively for grounding (earthing).

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