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Domestic Electric Circuit

Electric power is usually generated at places which are far from the places where it is consumed.

Distribution of Electricity from Grid

The power is transmitted over long distances at high voltage to minimize the loss of energy during transmission. For agiven electric power, the current becomes low at a high voltage and therefore the loss of energy due to heating H aI2)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 substation. At the city sub-station it is further stepped down to 110 V and supplied to the consumer.

Sub Topics

Supply to a House

House Wiring

Supply to a HouseBack to Top

The electric power line enters our house through three wires. One is called the earth wire or ground wire. This carriesno electricity. The earth wire is connected to a large metal plate buried deep in the ground. The remaining two wirescarry electricity. One of these is maintained at zero potential by connecting it to the earth at the power station itselfand this wire provides the return path for the current. This wire is called the neutral wire. The other wire is at a highpotential. This wire is called the live wire. In fact potential of this wire changes from positive to and negative againnegative to positive, 60 times per second. This is called 60 Hz AC The current in any appliance accordingly changesits direction 60 times in a second. The effective average magnitude of the potential difference is 110 V. That is why i tis called 110 V, 60 Hz AC supply.

All electrical appliances are connected across the neutral and live wires. The same potential difference is thereforeapplied to all of them and hence these are connected in parallel to the power source.

There is a color convention for wiring. According to this convention, the live line is carried by a wire with blackinsulation, the neutral by a wire with white insulation and the earth by a wire with green insulation. It is important thata live wire is not allowed to come in contact with the neutral or the earth wire. In this case, the circuit is completedwith a negligible resistance and hence a large current flows through the wires. A lot of heating occurs in the wire andthis may lead to accidents. So it is advisable to use correct color codes so that the chances of wrong connections arereduced.

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