Friday 14 May 2010

Lightning conductors

One of the great things about being a bell ringer is that I get to up the church tower. You get the best view of Wigton from the top. Notice the thick metal strip running down from the spike at the top. It's a lightning conductor. It goes all the way down the outside of the tower and is then concreted into the ground. The idea is twofold:
1. If lightning does strike, the massive current is carried down the metal, which has a much lower resistance than the masonry. This stops the masonry overheating and the mortar being broken.
2. It actually deters lightning. If the cloud has a large positive charge, it attracts electrons, which are negative, up from the ground to the tip of the spike. The large concentrated charge ionises the air molecules and then repels negative ions up to the positive charge. This neutralises some of the charge, making lightning less likely.