Domestic Electric Circuit
The power is transmitted over long distances at high voltage to minimize the loss of energy during transmission. For a given electric power, the current becomes low at a high voltage and therefore the loss of energy due to heating H a I2)becomes less. So the alternating voltage is stepped up at the generating station. It is then transmitted to the main sub-station. This voltage is stepped down and is transmitted to the switching transformer station or the city sub station. At the city sub-station it is further stepped down to 110 V and supplied to the consumer.
Supply to a House
There is a color convention for wiring. According to this convention, the live line is carried by a wire with black insulation, the neutral by a wire with white insulation and the earth by a wire with green insulation. It is important that a live wire is not allowed to come in contact with the neutral or the earth wire. In this case, the circuit is completed with a negligible resistance and hence a large current flows through the wires. A lot of heating occurs in the wire and this may lead to accidents. So it is advisable to use correct color codes so that the chances of wrong connections are reduced. The appliances used in our house need 110 V of potential difference between their live and neutral terminals. But the current drawn is different for different appliance. The current requirement of heaters is around 10 A, and that of the bulb is order of 1 ampere. So two types of switches and sockets are available in the market, one meant for a minimum current of 5A and other for a maximum of 15A. The appliances drawing heavy currents are connected to the 15A - boards and other to the 5A - boards.