Concepts and Terminology
– Plugs and sockets connect electric equipment to AC mains electricity
– They differ in voltage, current rating, shape, size, and connector type
– Different standard systems of plugs and sockets are used worldwide
– Portable appliance plugs and sockets were introduced in the 1880s
– Approximately 20 types of plugs and sockets are in common use globally
History
– Commercial electric power was initially used for lighting in the 1880s
– Two-pin plugs and wall sockets were available in Britain by 1885
– Three-pin earthed plugs appeared around 1910
– Safety improvements were gradually introduced over time
– The first national standard for plug and socket forms was set in 1915
Application Issues
– Plug and socket designs aim to reduce the risk of electric shock and fire
– Plugs are shaped to prevent bodily contact with live parts
– Sockets may be recessed to reduce the risk of contact with live pins
– Contact pins may be insulated to minimize exposure of energized metal
– Sockets may have automatic shutters to prevent foreign object insertion
Protection from Accidental Contact
– Plugs and sockets have safety features to prevent electric shock
– Plugs are designed to avoid contact with live parts
– Sockets may be recessed to reduce the risk of touching live pins
– Contact pins can be sheathed with insulation during insertion and removal
– Sockets may have automatic shutters to prevent insertion of foreign objects
Earthing (Grounding)
– Earthing pins protect against insulation failure of connected devices
– Early unearthed plug and socket types were revised to include earthing
– The plug design ensures the earth ground contact connects first
– IEC appliance class determines the need for earthing or double insulation
– Class I equipment requires an earth contact, while Class II is unearthed Source: https://en.wikipedia.org/wiki/AC_power_plugs_and_sockets
AC power plugs and sockets connect devices to mains electricity to supply them with electrical power. A plug is the connector attached to an electrically-operated device, often via a cable. A socket (also known as a receptacle or outlet) is fixed in place, often on the internal walls of buildings, and is connected to an AC electrical circuit. Inserting ("plugging in") the plug into the socket allows the device to draw power from this circuit.
Plugs and wall-mounted sockets for portable appliances became available in the 1880s, to replace connections to light sockets. A proliferation of types were subsequently developed for both convenience and protection from electrical injury. Electrical plugs and sockets differ from one another in voltage and current rating, shape, size, and connector type. Different standard systems of plugs and sockets are used around the world, and many obsolete socket types are still found in older buildings.
Coordination of technical standards has allowed some types of plug to be used across large regions to facilitate the production and import of electrical appliances and for the convenience of travellers. Some multi-standard sockets allow use of several types of plug. Incompatible sockets and plugs may be used with the help of adaptors, though these may not always provide full safety and performance.
