Where the american put the ring and how he fixed it there.
Chapter name- Case of sharp eyed Jeweller
Answers
Answer:
In electricity supply design, a ring final circuit or ring circuit (often incorrectly called a ring main, a term used historically,[1] or informally a ring) is an electrical wiring technique developed and primarily used in the United Kingdom, and to a lesser extent in Ireland. 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.
ExplIdeally, 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.
The ring starts at the consumer unit (also known as fuse box, distribution board, or breaker box), visits each socket in turn, and then returns to the consumer unit. The ring is fed from a fuse or circuit breaker in the consumer unit.
Ring circuits are commonly used in British wiring with socket-outlets taking fused plugs to BS 1363. Because the breaker rating is much higher than that of any one socket outlet, the system can only be used with fused plugs or fused appliance outlets. They are generally wired with 2.5 mm2 cable and protected by a 30 A fuse, an older 30 A circuit breaker, or a European harmonised 32 A circuit breaker. Sometimes 4 mm2 cable is used if very long cable runs (to help reduce voltage drop) or derating factors such as very thick thermal insulation are involved. 1.5 mm2 mineral-insulated copper-clad cable (known as pyro) may also be used (as mineral insulated cable can withstand heat more effectively than normal PVC) though more care must be taken with regard to voltage drop on longer runs. The protection devices for the fixed wiring need to be rated higher than would protect flexible appliance cords, so BS 1363 requires that all plugs and connection units incorporate fuses appropriate to the appliance cord.
The ring circuit and the associated BS 1363 plug and socket system were developed in Britain during 1942–1947.[2] They are commonly used in the United Kingdom and to a lesser extent in the Republic of Ireland. They are also found in the United Arab Emirates, Singapore, Hong Kong, Beijing, Indonesia and many places where the UK had a strong influence, including for example Cyprus and Uganda.
Pre-World War II practice was to use various sizes of plugs and sockets to suit the current requirement of the appliance, and these were connected to suitably fused radial circuits, the ratings of those fuses were appropriate to protect both the fixed wiring and the flexible cord attached to the plug.
The Electrical Installations Committee which was convened in 1942 as part of the Post War Building Studies programme determined, amongst other things, that the ring final circuit offered a more efficient and lower cost system which would safely support a greater number of sockets.[3] The scheme was specified to use 13 A socket-outlets and fused plugs; several designs for the plugs and sockets were considered. The design chosen as the British Standard was the flat pin system now known as BS 1363. Other designs of 13 A fused plugs and socket-outlets, notably the Wylex and Dorman & Smith systems, which did not conform to the chosen standard, were used into the 1950s, but by the 1960s BS 1363 had become the single standard for new installations.
There is a common misperception that the ring circuit was devised to combat the post-war copper shortage, but this is not supported by the textual record.
The ring circuit is still the most common mains wiring configuration in the UK, although both 20 A and 30 A radial circuits are also permitted by the Wiring Regulations, with a recommendation based on the floor area served (20 A for area up to 25 m2, 30 A for up to 100 m2.).
Rules for ring circuits provide that the cable rating must be no less than two thirds of the rating of the protective device. This means that the risk of sustained overloading of the cable can be considered minimal. In practice, however, it is extremely uncommon to encounter a ring with a protective device other than a 30 A fuse, 30 A breaker, or 32 A breaker, and a cable size other than those mentioned above. Because the BS 1363 plug contains a fuse not exceeding 13A, the load at any one point on the ring is limited.