Electrical Circuits

An electrical circuit is a network that has a closed loop, giving a return path for the current. A network is a connection of two or more components, and may not necessarily be a circuit. Electrical networks that consist only of sources (voltage or current), linear lumped elements (resistors, capacitors, inductors), and linear distributed elements (transmission lines) can be analyzed by algebraic and transform methods to determine dc response, ac response, and transient response. A network that also contains active electronic components is known as an electronic circuit. Such networks are generally nonlinear and require more complex design and analysis tools.

To design any electrical circuit, either analog or digital, electrical engineers need to be able to predict the voltages and currents at all places within the circuit. Linear circuits, that is, circuits with the same input and output frequency, can be analyzed by hand using complex number theory. Other circuits can only be analyzed with specialized software programs or estimation techniques. Common designs for circuits are ring, radial and lighting. A ring final circuit or ring circuit (informally also ring main or just ring) is an electrical wiring technique developed that provides two independent conductors for live, neutral and protective earth within a building for each connected load or socket. This design enables the use of smaller-diameter wire than would be used in a radial circuit of equivalent total current. Ideally, the ring 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 current-carrying capacity. In practice, the load does not always split evenly, so thicker wire is used. Radial circuits- these circuits have a twin and earth cable running from the consumer unit to each of the socket outlets or fused connection units in turn, one after another, but it stops at the last one.

There is no return cable back to the consumer unit from the last socket or unit. There is no limit to the number of socket outlets / fused connection units supplied, and spurs may be added. The cable used and the fuse required may differ from a ring main, depending on the application. Large appliances often have to be on their own circuit. Lighting circuits- the main electric lighting circuits are separate from the power ring main circuit. Each house should ideally have at least two lighting circuits; each protected by a 5 amp fuse or 6 amp trip in the consumer unit. A single 5/6 amp circuit can cope with up to twelve 100 watt lamps, it is usual in a multi-storey house, to have at least one lighting circuit for each floor even if the number of lamps are less than 12 on each level.