Before starting with Class 6 Science Chapter 9 i.e. ‘Electricity and Circuits’, I am hoping that you have completed the 8th chapter. If not, then you can go through its Notes and NCERT Exercise Solutions whose links have been provided below. ⤵️
Table of Content
Introduction
Electricity and electric bulbs have proven themselves as one of the biggest boon for mankind.
We use electricity for a whole lot of purposes like lighting up our homes at night, refrigerators, air conditioners, electric irons, electric stoves, electric vehicles, etc.
Sometimes, when we have an electric power cut at night we use electric torches.
An electric torch is a device that has an electric bulb and electric cell(s) in it and when it is turned on it lights up.
Electric Cell
An electric cell is a device that converts chemical energy into electrical energy.
It provides electric energy to various appliances like electric torches, alarm clocks, wristwatches, cameras, etc
An electric cell has a small metal cap on one side known as the positive terminal of the cell.
And, it has a metal disc on the other side known as the negative terminal of the cell.
An electric cell produces energy from the reaction of the chemicals that it is filled with and when all the chemicals are used up the electric cell stops producing electricity.
An Electric Bulb
It is a device that glows up or gives light when electricity passes through it.
- A bulb has an outer glass case fixed on a metallic base/case.
- The thin wire inside the glass that gives off light when electricity passes through it is called a filament.
- The filament is fixed on two thicker wires which provide support to it.
- One of these thick wires is connected to the metal case making the negative terminal of the bulb.
- The other thick wire is connected to a metallic tip present at the centre of the base of the metallic case making the positive terminal of the bulb.
- The positive and the negative terminals of a bulb don’t touch each other.
Both an electric bulb and an electric cell have two terminals.
Precaution: Never join the two terminals of an electric cell directly without connecting them through a switch or a device like an electric bulb. Because, if you do so, then the chemicals in the cell will be used up fastly and the cell will stop working.
A Bulb Connected to An Electric Cell
Now that we have learned about an electric cell and an electric bulb, we have also learned that each one of them has two terminals.
So, now let’s try connecting their terminals together and see what happen.
- Take 4 different coloured metallic wires.
- Connect two wires to the terminals of the cell and the remaining two with the terminals of the bulb.
- And try to join the wires of the bulb and cell together in different patterns to see what happens.
Why did the bulb only glow in the ‘E’ arrangement, not in any other arrangements?
Well, to answer this question we have to understand the concept of electric circuits.
An Electric Circuit
Such an arrangement in which two terminals of a bulb are connected with the other two terminals of a cell is called a circuit or a closed loop like in ‘D’ and ‘E’ arrangements.
An electric circuit is a closed loop that provides a complete path for the electricity (current) to flow/pass from the positive terminal to the negative terminal of an electric cell or battery.
A battery is a combination of two or more electric cells.
The direction of current or electricity is from the positive terminal to the negative terminal.
But, both ‘D’ and ‘E’ arrangements are closed electric circuits but why did the bulb only glow up in the ‘E’ arrangement not in ‘D’?
This has something to do with the connection of wire, we connect the positive terminal of a cell to the positive terminal of a bulb and the negative terminal of a cell to the negative terminal of a bulb for the circuit to work properly. Hence, only the ‘E’ circuit has the current flowing in it that has lit up the electric bulb.
But, sometimes even if the circuit is good, the bulb won’t light up this may be because of a fused bulb.
Fused Bulb: A bulb with a broken filament is known as a fused bulb.
A fuse bulb breaks the circuit preventing the flow of electric current from the positive terminal of the cell to the negative terminal.
A bulb can get fused due to various reasons.
Electric Switch
The bulb in the arrangement ‘E’ will keep on lighting itself till the complete exhaustion of battery or cell.
So, we need something to voluntarily break and complete the circuit without disturbing the terminal connections.
So, we use a specific device, known as an electric switch.
An electric switch is a simple device that either breaks the circuit or completes it.
You can make this simple electric switch with a few drawing pins, safety pins and a piece of wood.
For this, you can refer to your Class 6 Science Chapter 9 in NCERT Textbook Page No.99.
Electric Conductors and Insulators
Have you ever wondered why we use metallic wires for connecting a cell with the bulb, not cotton threads or plastic wires?
Why is it that?
If we will replace the metallic wires with cotton thread or plastic wires then the light bulb with not light up.
This is because cotton thread and plastic don’t conduct electricity means they don’t allow electricity to pass through them.
Materials that allow electric current to pass through themselves are called electric conductors. e.g. metals like copper, aluminium, iron, gold, silver, graphite (pencil lead), the human body etc.
So, we make electric wires, electric plugs, switches, etc. with electrically conducting material.
And, materials that don’t allow the electric current to pass through themselves are called electric insulators. e.g. plastic, cotton, dry wood, rubber, etc.
So, we make the covering for the electric wires, sockets, and plugs with electrically insulating materials.
Conclusion
We should handle electricity with care as the human body is an electric conductor and electricity can easily pass through us giving us severe electric shocks, burns and in some cases, it can kill a person as well.
And, also don’t waste electricity in your daily life, use only as much as you are required.
References & Credits
- Class 6 Science NCERT Textbook
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