Lighting Rods：Actually Trigger Lightning To Ground？

As is known to all, lightning rod is a device used to protect buildings from lightning strikes. We might think that with the protection of lightning rod, the lightning will escape and can’t contact with the building. However, that is a misunderstanding. In this passage, we will briefly introduce the invention of lightning arrester and the theory how it functions.

The Invention of Lightning rod

Modern lightning rods were invented by American scientist Franklin. He believes that lightning is a kind of discharge. To prove this, in a thunderstorm day in 1752, Franklin risked being struck by lightning. He flew a kite with long metal wires into the thundercloud and smashed at the end of the metal with a bunch of silver keys. When lightning strikes, Franklin approaches the key with his hand, and a string of electric sparks enters the key, and his hand is numb. Fortunately, the lightning that was passed down this time was weaker, and Franklin was not injured. Franklin thus imagined that if it could be at a higher object. By placing a tip device on the body, it is possible to introduce lightning into the ground. He fixed a few meters long thin iron rods on the top of the tall building, separated the iron rod from the building with an insulator, and then connected the bottom end of the iron rod with a wire, and then introduced the wire into the ground. After testing, this device, which is called lightning rods by Franklin, can play a role in lightning protection.

The Theory How Lightning Rod Functions

Actually, lightning rod is triggering lightning to the ground. 

At first, the lightning rods were designed to be needle-shaped. Since the needle of the lightning rod is pointed, the tip of the conductor always collects the most charge when it is electrostatically induced. Therefore, when lightning strikes, the lightning rod will accumulate most of the charge. At the same time, the lightning rod and the charged cloud layer form a capacitor, which means a charged container. Because of its sharpness, the two plates of this capacitor have a small opposing area and a small capacitance, which means that it can hold a small amount of charge. 

The lightning rod accumulates most of the charge, so when there is more charge on the cloud, the air between the lightning rod and the cloud layer is easily broken down and becomes a lightning conductor. In this way, the charged cloud layer forms a path with the lightning rod. The lightning rod is grounded again, which can push the charge on the cloud to the ground, so that it does not pose a danger to the high-rise building, thus ensuring the safety of the building. It can be seen that the lightning protection effect of the lightning rod is that it leads lightning from above the protection to itself and safely vents to the earth through itself. Therefore, we can also call it as lightning protection. All in all, the lightning needle is actually triggering the lightning to the ground.