I watched some videos and read a lot of posts mentioned that pointy shaped objects create denser electric field than other objects (especially spherical ones), that's why people use pointy and conductive metals to make lightning rods. As the clouds started to gather charges ( usually negative ions ) the lightning rods with high electric field will attract the charges so that the clouds cannot create high enough voltage to ionize the air between them and the ground. However, the lightning rods are still struck sometimes. And this is what I wonder: When the lightning rods are struck, does it mean that the clouds gather charges faster than the rods? And do the sparks only happen when there is a huge amount of ions in the air and when they recombine to form neutral particles, they emit energy in the form of light which makes the lightning glow?
1 Answer
A positive cloud overhead will attract electrons and cause a significant build up of negative charge in the ground (or water) below it. A high, sharp, well grounded rod can bleed this induced charge into the air, reducing the field between cloud and ground, and reducing the probability of a strike. I'm not sure that this would work for a negative cloud. I have endured several lightning storms while anchored in shallow (salt) water in my sailboat (some well offshore). My boat has a sharpened metal ribbon clamped to the top of the mast, and I drop grounding wires from the side stays into the water. The one strike that I am aware of sounded more like a sizzle than a boom. At home, my outside TV antenna post has a similar ribbon at the top and it has been struck at least twice (I think because the ground was dry, and my grounding rod does not go deep). (In south Florida we get a lot of lightning.)
