Lightning arrester or lightning conductor

A lightning arrester, also called a lightning conductor, is a device used to protect tall buildings from lightning strikes, and it works directly on the principle of action at points (corona discharge) established in section 1.9.2. It consists of a thin metal rod with a sharply pointed tip, mounted at the very top of a building, connected by a thick, low-resistance conducting cable running down the outside of the building to a metal plate buried in moist earth at ground level. During a thunderstorm, when the atmosphere above the building becomes strongly electrified, the sharp point at the top of the rod promotes a continuous, gentle corona discharge, bleeding charge steadily away between the building and the surrounding air and thereby reducing the chance that a large, sudden potential difference builds up. Should a direct lightning strike occur despite this, the arrester's thick conducting cable provides a ready, low-resistance path that safely carries t …