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  • NEMA connector


    Ungrounded and grounded power plugs Common North American 125 volt receptacles. All accept a 1-15P plug; the two on the left also accept 5-15P plugs. The NEMA 5-15R device on the far left is most common; the designs on the right are typically seen in older buildings. NEMA 5-15P plug and NEMA 5-15R receptacle (different scales, blade spacing is for both.) Each receptacle also accepts an ungrounded plug, whether polarized or unpolarized.NEMA connectors are power plugs and receptacles used for AC mains electricity in North America and other countries that use the standards set by the US National Electrical Manufacturers Association. NEMA wiring devices are made in current ratings from 15 to 60 amperes (A), with voltage ratings from 125 to 600 volts (V). Different combinations of contact blade widths, shapes, orientation, and dimensions create non-interchangeable connectors that are unique for each combination of voltage, electric current carrying capacity, and grounding system.

  • AC power plugs and sockets


    AC power plugs and sockets allow electric equipment to be connected to the primary alternating current (AC) power supply in buildings and at other sites. Electrical plugs and sockets differ from one another in voltage and current rating, shape, size, and connector type. Different systems of plugs and sockets have been standardized, and different standards are used in different parts of the world. Plugs and sockets for portable appliances became available in the 1880s, to replace connections to light sockets (often in ceiling fixtures) with lower, wall-mounted outlets. A proliferation of types developed for both convenience and protection from electric shock. Today there are about 20 types in common use around the world, and many obsolete socket types are found in older buildings. Coordination of technical standards has allowed some types of plug to be used across large regions to facilitate trade in electrical appliances, and for the convenience of travellers and consumers of imported electrical goods.

  • Ring circuit


    In electricity supply design, a ring final circuit or ring circuit (often incorrectly called a ring main or informally a ring) is an electrical wiring technique developed and primarily used in the United Kingdom. This design enables the use of smaller-diameter wire than would be used in a radial circuit of equivalent total current. The reduced diameter conductors in the flexible cords connecting an appliance to the plug intended for use with sockets on a ring circuit are individually protected by a fuse in the plug. Its advantages over radial circuits are therefore reduced quantity of copper used, and greater flexibility of appliances and equipment that can be connected. Ideally, the ring circuit acts like two radial circuits proceeding in opposite directions around the ring, the dividing point between them dependent on the distribution of load in the ring. If the load is evenly split across the two directions, the current in each direction is half of the total, allowing the use of wire with half the total current-carrying capacity. In practice, the load does not always split evenly, so thicker wire is used.

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