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Theory:

Earthing:
A safety measure to prevent people from getting electrical shock by electrical devices' insulation failure is called earthing. Electrical earthing can be defined as transferring the discharge of electrical energy directly to the earth with a low resistance wire.
  • We get electrical energy from different sources. Battery is one of them. We use them in wall clocks, toys, cell phones, etc,.
  • We use domestic power supply for refrigerators, air conditioners, washing machines, televisions, laptops, and water heaters.
  • Usually, electric appliance such as heaters, iron boxes, etc., are fitted with three wires: live, neutral, and earth.
  • The earth wire is connected to the electrical appliance's metallic body, such as an iron box or heater. This is done to avoid electrical shock. Suppose the live wire insulation burns due to some defect; then, the live wire may touch the metallic part of the electrical device.
  • If the earth wire is connected correctly to the metallic body, current will pass into the earth through the earth wire, protecting us from electric shock.
  • The earthing plate acts as a convenient path for the flow of electric current that leaks out from the insulation, thereby protecting us from electrical shock.
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Three-pin plug
 
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The picture shows the parts of a three-pin plug
  
Lightning arrestors:
A lightning arrestor is a device used to protect buildings from the effects of lightning. The lightning conductor consists of a metallic rod (in the form of spikes) that remains in the air at the top of the building.
  • A major part of the metal rod and copper wire are installed in the walls during the construction.
  • The other end of the rod is fixed deep into the soil. When the lightning falls, it is attracted by the metallic rods at the top of the building.
  • Thus, the rod provides an easy way for transferring electric charges to the ground without affecting the building. In the absence of lightning arrestors, lightning will fall directly on the building, and the building will be damaged.
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The picture shows the protection of building from lightning.