What is a lightning conductor? How does it save high rise buildings from lightning damage?

Hint:Electric field inside the conductor is zero. This is due to induction of charges inside the conductor when charged clouds come near it.

Complete step by step answer:
 A lightning conductor is used to save big buildings from the damage by lightning flashes.
A lightning conductor consists of a number of pointed conductors fixed to the top of a building and connected to a thick copper wire. This wire runs down the side of the building and ends on a metal plate buried in the ground.

When a negatively charged cloud passes over the building, it induces a positive charge on the pointed ends of the lightning conductor and an equal negative charge at the metal plate. Due to discharging action of sharp points, a positively charged electric wind is set up, which neutralises the negative charge on the cloud. The negative charge on the metal plate is immediately neutralized in the earth. If the discharge of the cloud occurs, it passes through the conducting copper strip and the building is saved from the damage.

Note: Electric field inside the conductor is zero that’s why it is safer inside a metallic cage than under a tree during lightning. During lightning the conductor mounted on top of the building neutralizes flow of charge with lightning.