Q. Assertion: The lightning conductor at the top of high building has sharp pointed ends.
Reason: The surface density of charge at sharp points is very high resulting in setting up of electric wind.

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Solution:

We know that surface density of charge is very large on the sharp ends of a conductor. This charge from pointed ends sets up a charged electric wind. This charged electric wind comes in contact with the charged clouds and then source of its charge is neutralized and so potential drops between building and clouds. Hence, chances of lightning on building is reduced. Even if lightning strikes the building, charge is conducted by the lightning conductor to the earth and there is no harm to building.