List four important features of domestic electric circuits. Draw a schematic diagram of common domestic circuit showing live, neutral and earth wires.
CBSE Class X Science LA (5 Marks)
Answers
(i) Appliances to be connected in parallel.
(ii) Each appliance has a separate switch to ON/OFF the flow of current through it.
(iii) In each circuit different appliances can be connected across the live wire and the neutral wire.
(iv) Fuse connected to avoid damage
The main features of domestic wiring are:
(i) The electric supply from the mains is delivered to our homes using a three core cable. Three core cable is usually overhead electric poles or underground cables. One of these wires with red insulation cover is called live wire which brings in the current. The second wire with black insulation is called neutral wire which provides the return path for the current. The third wire is the earth wire. The potential difference between live wire and neutral wire is 220 volts in India.
(ii) The earth wire is either thick uncovered copper wire or a copper wire with green insulation. It is usually connected to a metal plate deep under the earth near the house. Earthing is used as a safety measure to protect the supply from any damage.
(iii) The wires from the supply line pass into the watt-hour-meter through a main fuse. These wires enter a distribution box through a main switch. From the distribution box, several independent distribution circuits are drawn which go into different parts of the house. The live wire of each circuit passes through a separate fuse so that during short circuiting, only the electricity to that part of the house is cut off and others are not affected.
(iv) In any part of the house, all appliances are connected in parallel to each other across the live and neutral wires. This ensures full voltage across each appliance from the mains. Each appliance is provided with a separate switch in its live wire for its operation.
(v)Two separate circuits are used. For appliances with high power rating such as geysers, air conditioners etc. 15 A current rating is used. The other circuit of of 5 A for low power appliances.
