Table of Contents
- Earthing of electrical appliances
- Electric Fuse
- Precaution in the Use of Electricity
Electricity is generated at the power station and comes to the substation then comes to the nearest powerhouse then comes to the nearest transformer(step down) near to our house then comes to our house with line wire(L) and neutral wire(N). This is the final process. With the help of a step-down transformer, voltage is stepped down and sends only 220-230 Volt to your home.
In two wires, one is Line(L) and another is Neutral(N). So potential difference between Lines and Neutral is (230-0=230V)
- Usually, a house has two separate circuits: the lighting circuit with a 6A fuse and the power circuit with a 16A fuse.
- Each distribution circuit is provided with a separate fuse so that if a fault like short-circuiting occurs in one circuit, its corresponding fuse blows off, but the other circuit remains unaffected.
- Our house wiring is connected in parallel, the benefit of parallel wiring is if one equipment is damaged another is still working.
- To distinguish between the live wire, neutral wire and earth wire, the wire having red plastic covering is made live wire, the wire having black plastic covering is made neutral wire and the wire having green plastic covering is made earth wire.
- All the electrical appliances are provided with separate switches and separate fuse in every board.
- Now instead of a switch, MCB(Miniature circuit Breaker) are used. It is a fast trip to save equipment.
[1] Earthing of electrical appliances:
- To avoid the risk of electric shocks, the metal body of an electrical appliance is earthed.
- If any shock applied to our body, the high current through the earth wire goes to earth, we know that the earth has zero potential, so it absorbs all current, saving us from electric shocks.
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| Wire with line, neutral and earth wire |
[2] Electric Fuse:
If the current passing through wires exceeds this maximum value, the copper wire gets overheated and may even cause a fire. An extremely large current can flow in domestic wiring under two circumstances, Short-circuiting and overloading. To protect from this happening we use a fuse.
- Short Circuiting:-Touching of the live wire and neutral wire directly is known as a short circuit.
- Over Loading:-The current flowing in domestic wiring at a particular time depends on the power rating of the appliances being used. If too many electrical appliances of high power rating(like electric iron, heater etc.) are used at the same time, they draw an extremely large current from the circuit. They can damage the circuit. This is known as overloading.
- To save the circuit from Short Circuits and Overloading, we use a fuse in series with the line.
- A fuse is a safety device having a short length of thin Tin-plated copper wire having a low melting point, which melts and breaks the circuit if the current exceeds a safe value.
- An electric fuse works on the heating effect of current.
- A fuse wire is connected in series in the electric circuit.
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| Electrical fuse |
- The fuse wire must have the proper thickness, which depends on the maximum current that the household's wiring can safely carry.
- Now MCB(Miniature Circuit Breaker) is used in domestic wiring instead of a fuse because of its safe and faster response than a fuse.
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| MCB |
- Fuses are also used to protect individual domestic electrical appliances from damage which may be caused due to excessive current flow through them.
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| Symbol and Picture of Electrical fuse |
[3] Precaution in the use of Electricity:
To avoid hazards like electric shocks or electric fires, we should observe the following precautions in the use of electricity
- Never touch switches or sockets with wet hands.
- Never touch line wire with a bare hand.
- A fuse should always be connected to the live wire of the circuit. The fuse wire should be of proper rating and material.
- The household wiring should be done by using good quality wires having proper thickness and insulation.
- We should avoid working on a Live wire(L) circuit for repairs.
- All the big power appliance that comes in contact with daily should always connect to earth wire for the presentation of electric shocks.