Question

Explain the working of domestic circuits.

Answer 1

At our homes, we receive the electric power supply through a main supply (called mains), either supported through overhead electric poles or by underground cables. One of the wires in this supply, usually with red insulation cover, is called live wire (or positive), the other, with black insulation, called neutral wire (or negative).   In India, the potential difference between live wire and the neutral wire is 220 V. At the metre-board of our homes, these wires pass into the electric meter through the main fuse. Through the main switch live wire and the neutral wire are connected to the line wires in the house. These wires supply electricity to separate circuits within the house.     Often, two separate circuits are used, one of 15 A current rating for appliances with higher power ratings such as Washing machines, geysers, air coolers, etc. The other circuit is of 5 A current rating for bulbs, fans, etc.   The wire which has insulation of green colour is usually connected to a metal plate deep in the earth near the house. This is used as a safety measure; especially for those appliances that have a metallic body is called the earth wire,        Example   The metallic body of electric press, toaster, table fan, refrigerator, etc. is connected to the earth wire, which provides a low-resistance conducting path for the current. Thus, it ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth, and the user may not get a severe electric shock.   In each separate circuit, different appliances can be connected across the live and neutral wires. Each appliance has a separate switch to ‘ON’/‘OFF’ the flow of current through it. Each appliance is connected parallel to each other, as each appliance has equal potential difference.   Electric fuse: Electric fuse is an important component of all domestic circuits. the principle and working of a fuse is to prevent the  damage to the appliances and the circuit due to overloading.   Overloading: Overloading takes place when the live wire comes into direct contact with the neutral wire (This occurs when the insulation of wires is damaged or there is a fault in the appliance.) In such a situation, the current in the circuit abruptly increases. This is called Short-circuiting   What is short-circuiting?   The use of an electric fuse prevents the electric circuit and the appliance from a possible damage by stopping the flow of unduly high electric current. The Joule heating that takes place in the fuse melts it to break the electric circuit. Overloading can also occur due to an accidental hike in the supply voltage. Sometimes overloading is caused by connecting too many appliances to a single socket.   Short circuit:  When the circuit offers zero or negligible resistance to the flow of current, the circuit is said to be short circuited.  Short circuit takes place when live wire and the neutral wire touch each other due to the following   i)  Faulty appliances ii) Damage in the insulation of two wires.                   According to Ohm’s law, large amount of current flows through the circuit of low resistance   According to Joule’s law of heating effect, heat is produced in the live wire (Hα I2) and produces spark damaging the devices and wiring at the place of short circuit.    Over loading:  If the total current drawn by all the appliances at a particular time exceeds the bearing capacity of that wire, the wires of the domestic wiring get heated, is called overloading It takes because of the following reasons i) Accidental rise in supply voltage ii) Connecting many devices to the same (one single) socket.           Earthing Earthing is the process of connecting the exposed metal parts of an electrical circuit to the groundUsually an electric appliance such as a heater, an iron box, etc. are fitted with all the three wires namely live, neutral and earth. The earth wire is connected to the metallic body of the appliance. This is done to avoid accidental shock. Suppose due to some defect, the insulation of the live wire inside an electric iron is burnt then the live wire may touch the metallic body of the iron.      When the iron box is in use, the metallic body will also be increased to 110V. If we accidentally come in contact with such a metallic body we are sure to get an electric shock. If the earth wire is properly connected to the metallic body it protects us from an electric shock.

Answer 2

An electricity meter, electric meter, electrical meter, or energy meter is a device that measures the amount of electric energyconsumed by a residence, a business, or an electrically powered device.

Electric utilities use electric meters installed at customers' premises for billing purposes. They are typically calibrated in billing units, the most common one being the kilowatt hour(kWh). They are usually read once each billing period.