ELECTRICITY AT HOME
We know that electricity is generated at power stations, from where it is sent to city substations through cables and poles at many thousand volts. These substations send electricity to transformers which the bring down the electricity 10 220 volts and transfer it to our homes. The cables which supply electricity our homes first pass through the mains board which has an electric meter and a fuse box The electroly after passing through the electric meter, which measures the amount of electricity we use, goes through the main fuse box. The fuse is a safety device whose function is to prevent electric hazards. From the ma fuse box, electricity is sent to different parts of the house for various purposes. • The live wire carries the electrical current supplied by the source (transformer through electric poles) to the electrical appliances. It is given an insulation of red or brown colour.
• The neutral wire completes the circuit by returning the electricity to the source (transformer) after it has passed through the appliance. It can be identified by black or blue colour.
• The earth wire has no current flowing through it. One end of the earth wire is connected to the appliance and the other end is grounded. Any leakage of current in the appliance flows to the earth and we do not get any electric shock due to earthing. Therefore, the earth wire is a safety wire. It is usually of green or yellow colour.The wiring in houses, schools and offices is done in such a way that all the devices are connected in parallel so that they can work independently. This is why if you switch off the lights and fans of your room, the other electric equipments in the house do not turn off or disturb other appliances in the house.
Sockets, Plugs and Switches
Home appliances are connected to the electric supply with the help of plugs and sockets. All the appliances are provided with plugs which are either two-pin or three-pin. The outer part of a plug called the casing is made of plastic and is a good insulator. This is done to ensure safety against electric shocks. Connections to the circuits are made via three brass pins, as brass is an excellent conductor of electricity. We generally use three-pin plugs. The lower two pins are the terminals out of which one is connected to the live wire and the other to the neutral wire. The topmost pin is connected to the earth. To run any equipment the plug is
Beside the plug and the socket, a switch is also needed. It is an on/off key, which is used to open and close a circuit. The outer panel of a switch is always made up of insulators to avoid electric shocks. The inner side is made up of conducting materials like brass and is connected to the live wire.
A battery is a combination of two or more cells joined together in series via conducting wires. The cells are connected in such a way that the positive terminal of one cell is connected to the negative terminal of the other cell. Just like cells, batteries are of two types-primary batteries which are designed to be used once and discarded, and secondary batteries which are designed to be recharged and used a number of
Batteries made by connecting secondary cells are known as storage batteries or accumulators. Batteries are available in different sizes ranging from the button size used in watches to the larger ones used in cars and invertors
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