In the previous section we saw the details about household circuits. We also saw the kwh meter. In this section, we will see the details about 3 pin plug.
1. Consider the fig.12.8 shown below. It shows the inside of an electric iron.
• The current enters the heating coil from the phase line shown in red colour.
• It leaves the coil through the neutral line shown in black colour.
• Due to this flow of current, the required heat is produced in the coil.
2. If there is any fault in the insulation, the current will enter the body of the iron.
• In such a situation, a person who touches the iron will get an electric shock.
3. Such an accident can be avoided by using a 3 pin plug.
Let us see how the three pin plug helps to avoid the accident:
• Fig 12.9 below shows different types of 3 pin plugs available in the market
4. The basic functioning of all of them are the same.
• There are two small pins and one large pin.
♦ The large pin is called the earth pin
♦ Among the two smaller pins, one is for phase line and the other is for the neutral line.
5. Now consider figure 12.8 again.
• A green wire starts from the body of the iron. It enters into the three pin plug.
• Inside the three pin plug, this green wire is connected to the earth pin. This is shown in fig.12.10 below:
6. So the current which has entered the body of the iron has two options:
(i) Flow into the body of the person who touches the iron
(ii) Flow into the earth through the green earth line
• Current will choose the second option because, it is a 'path of less resistance'
■ To make this flow more easier, the earth wire is always given a greater thickness
■ The earth pin also has a greater thickness
7. When the current thus begins to flow into the earth, more current will be drawn into the appliance
• Such a higher current will increase the temperature in the fuse wire.
• As a result, the fuse wire will melt and thus the circuit will become open. Danger is thus averted.
8. We can see that, the length of the earth pin is greater than the other two pins. Why is that so?
Ans: Consider the instant at which a person inserts the 3 pin plug into the socket
• Two things happen at that instant:
(i) The earth pin comes into contact with the 'earth line connecting the socket to the earth'
(ii) The phase pin and neutral pin come into contact with their respective lines, and current begins to flow
• Since the earth pin is longer, (i) happens before (ii)
• So the 'whole earth line from the appliance to the earth' will be ready before the flow of current begins.
• If any current enters the body of the appliance, 'a path is already waiting' for it's easy flow into the earth.
9. Consider the instant at which the person pulls the plug out of the socket
• Two things happen at that instant:
(i) The earth pin loses it's contact with the 'earth line connecting the socket to the earth'
(ii) The phase pin and neutral pin lose their contact with their respective lines, and current is cut off
• Since the earth pin is longer, (ii) happens before (i)
• So the 'earth line is fully capable to carry any current' even after the instant at which current from the phase line is stopped.
First aid to be given in the case of electric shock
■ First Aid should be given only after disconnecting the victim from the electric wire
• As a result of electric shock,
♦ The body temperature of the victim decreases
♦ Viscosity of blood increases
♦ Clotting of blood occurs
♦ Muscles of the body contract
■ How to provide first aid:
• Raise the temperature of the body by massaging
• Give artificial respiration
• Massage the muscles and bring them to the original condition
• Start first aid for the functioning of the heart (apply pressure on the chest regularly)
• Take the person to the nearest hospital immediately
1. Consider the fig.12.8 shown below. It shows the inside of an electric iron.
 |
| Fig.12.8 |
• It leaves the coil through the neutral line shown in black colour.
• Due to this flow of current, the required heat is produced in the coil.
2. If there is any fault in the insulation, the current will enter the body of the iron.
• In such a situation, a person who touches the iron will get an electric shock.
3. Such an accident can be avoided by using a 3 pin plug.
Let us see how the three pin plug helps to avoid the accident:
• Fig 12.9 below shows different types of 3 pin plugs available in the market
 |
| Fig.12.9 Source: https://commons.wikimedia.org/wiki/File:BS-546-3-pin-plugs.jpg |
• There are two small pins and one large pin.
♦ The large pin is called the earth pin
♦ Among the two smaller pins, one is for phase line and the other is for the neutral line.
5. Now consider figure 12.8 again.
• A green wire starts from the body of the iron. It enters into the three pin plug.
• Inside the three pin plug, this green wire is connected to the earth pin. This is shown in fig.12.10 below:
 |
| Fig.12.10 Source: https://commons.wikimedia.org/wiki/File:Three_pin_mains_plug_(UK).svg |
(i) Flow into the body of the person who touches the iron
(ii) Flow into the earth through the green earth line
• Current will choose the second option because, it is a 'path of less resistance'
■ To make this flow more easier, the earth wire is always given a greater thickness
■ The earth pin also has a greater thickness
7. When the current thus begins to flow into the earth, more current will be drawn into the appliance
• Such a higher current will increase the temperature in the fuse wire.
• As a result, the fuse wire will melt and thus the circuit will become open. Danger is thus averted.
8. We can see that, the length of the earth pin is greater than the other two pins. Why is that so?
Ans: Consider the instant at which a person inserts the 3 pin plug into the socket
• Two things happen at that instant:
(i) The earth pin comes into contact with the 'earth line connecting the socket to the earth'
(ii) The phase pin and neutral pin come into contact with their respective lines, and current begins to flow
• Since the earth pin is longer, (i) happens before (ii)
• So the 'whole earth line from the appliance to the earth' will be ready before the flow of current begins.
• If any current enters the body of the appliance, 'a path is already waiting' for it's easy flow into the earth.
9. Consider the instant at which the person pulls the plug out of the socket
• Two things happen at that instant:
(i) The earth pin loses it's contact with the 'earth line connecting the socket to the earth'
(ii) The phase pin and neutral pin lose their contact with their respective lines, and current is cut off
• Since the earth pin is longer, (ii) happens before (i)
• So the 'earth line is fully capable to carry any current' even after the instant at which current from the phase line is stopped.
First aid to be given in the case of electric shock
■ First Aid should be given only after disconnecting the victim from the electric wire
• As a result of electric shock,
♦ The body temperature of the victim decreases
♦ Viscosity of blood increases
♦ Clotting of blood occurs
♦ Muscles of the body contract
■ How to provide first aid:
• Raise the temperature of the body by massaging
• Give artificial respiration
• Massage the muscles and bring them to the original condition
• Start first aid for the functioning of the heart (apply pressure on the chest regularly)
• Take the person to the nearest hospital immediately
• Electricity is an integral part of everyday life. This energy is to be conserved for tomorrow and so its consumption should be reduced to the minimum possible level.
■ Saving electricity is equivalent to generating electricity
• Electricity is highly useful. And at the same time, it is a dangerous form of energy. Hence electrical appliances should be handled with extreme care
In the next chapter, we will see colors of light
Copyright©2018 High school Physics lessons. blogspot.in - All Rights Reserved
No comments:
Post a Comment