Question

Why is Earthing done in buildings?
A. To protect us from electric shock
B. To give extra strength to the building
C. To transfer extra current to air
D. None of these

Answer 1

Hint: If a building is struck by lightning it can cause devastating damage to the building and the people taking shelter in the building, so a lightning conductor is installed on the very top of the building in order to pave a very safe path for lightning to travel through it (metal wire).

Complete answer:
At high altitude due to friction with air the clouds get charged. This charged cloud induces an opposite type of charge to anything which is close to it. If the amount of induced charge is high enough this may start attracting the charges of the cloud towards itself (as opposite charges attract each other). If the attraction was successful then all the charges from the cloud moves to the object which had induced charge on itself thus a lightning occurs and we see white spark.

When a cloud passes close to a high building this induces charge to the building. Sometimes this induced charge gets very high enough that they start attracting the charged particles from the cloud. Thus, there is a chance that lightning may strike the building and can cause a devastating amount of damage to the building.

So, in order to protect the building from lightning a lightning conductor (made up of copper) is installed in the building which transfers all the charges from the cloud to the ground thus neutralizing it. The lightning rod is installed on the top of the building, since it is made up from a metal of high conductivity it gets charged very easily and then allows the current to flow through it very quickly (as current travels through the quickest route) via a copper wire or rod into the ground and our building is protected.A simple lightning conductor.

Therefore, the option A is correct.

Note: The charge carried by the cloud is static electric charges which is mainly caused by rubbing and friction when the electrons from one body gets transferred to another body, thus both the bodies acquire equal and opposite charge. Induction is the process through which a charge body induces an opposite charge in a body close to it. The amount of charge transfer occurs during lightning is very high, far more for a building to take.