How lightning forms
Airflow in thunderclouds will generate static electricity due to the friction and decomposition of water molecules. There are two types of electricity. One is positive electricity with positively charged particles, and the other is negative electricity with negatively charged particles. Positive and negative charges attract each other, like magnets.
The positive charge is at the top of the cloud, and the negative charge at the bottom of the cloud attracts the positive charge on the ground. The air between the clouds and the ground is an insulator, preventing the electric current from passing through the polar charges.
When the charges in the thundercloud and the charges on the ground become strong enough, the charges in the two parts will break through the obstruction of the air and come into contact to form a strong current, and the positive charges and negative charges will come into contact. When these opposite charges meet, neutralization occurs. Intense charge neutralization will release a large amount of light and heat, and the released light forms lightning.
Who invented the lightning rod and when?
The modern lightning rod was invented by Benjamin Franklin in 1753.
The French traveler Cabriolet Demagalin wrote in his book “News in China” in 1688: At both ends of the roof of China, there is a raised dragon head, with a twisting metal tongue spitting out from the dragon’s mouth. Pointing towards the sky, the base of the tongue is connected to a thin wire, which leads directly to the ground. If lightning strikes a house, the current will travel from the dragon’s tongue to the ground to prevent lightning from destroying the building. This shows that the lightning protection devices on ancient Chinese buildings are similar in structure to modern lightning rods.
What is a lightning rod?
Lightning rod, also known as air terminal. It is a device used to protect buildings and some tall trees from lightning damage. Install a lightning rod on the top of the object that needs to be protected, and then use a down conductor to connect the discharge grid buried underground.
It will attract lightning current to itself, and then discharge the lightning current to the earth through the down conductor and grounding device connected to the lightning rod, to protect the protected object from lightning strikes. Therefore, the essence of a lightning rod is to introduce lightning current into the ground, thereby protecting buildings, etc.
The specifications of lightning rods must comply with local standards. The specifications of lightning rods required for different lightning protection categories in different application scenarios will be different.
Lightning rods cannot completely prevent damage from lightning strikes. Lightning rods come in many shapes and styles, as well as many different conductive materials. Designed to smoothly guide lightning current to the earth.
What is the use and work lightning rod?
How lightning rods function
Installing lightning rods is an effective way to avoid lightning strikes. A metal rod is erected at the highest point of the house. The lower end of the rod is connected to a thick enough copper wire. The lower end of the copper wire is connected to a metal plate and buried deep in the ground in a moist place. The upper end of the metal rod must be pointed or bifurcated into several pointed ends. With such a device, when there are charged clouds in the sky. The tip of the lightning rod concentrates heterogeneous charges due to electrostatic induction, resulting in tip discharge, which neutralizes the electricity in the cloud to avoid violent lightning. This is one aspect of the lightning rod’s ability to protect against lightning.
But this effect is very slow. If electricity accumulates quickly in the cloud, or a cloud with a large amount of charge suddenly flies over, sometimes there is no time to neutralize it in the above way, so there is a strong discharge and lightning will still occur. But at this time, because the lightning rod is higher than the surrounding objects, its tip concentrates charges that are different from the electricity in the cloud. If lightning occurs between the cloud and the ground object, the discharge current mainly flows into the earth through the lightning rod, so there will be no strike. If it hits the house or people nearby, it will only hit the lightning rod.
It can be seen that the tip discharge of the lightning rod will reduce the possibility of lightning between ground objects and clouds; when it is inevitable, it will bear the lightning strike itself, and houses and people will be safe. Therefore, when installing a lightning rod, you need to ensure that the installation position is higher than any other nearby objects so that it comes into contact with lightning at the relatively closest position.
How lightning rods work
During thunderstorms, when charged clouds appear over high-rise buildings, a large amount of charge is induced on both the lightning rod and the top of the high-rise building. Because the needle of the lightning rod is pointed, and during electrostatic induction, the tip of the conductor always accumulates the most charge. In this way, the lightning rod collects most of the charges. The charged cloud will form a capacitor with the lightning rod. Because it is pointed, that is, the area of the capacitor’s two plates facing each other is very small, and the capacitance is also very small, which means that it can hold very little charge.
It carries too much charge, which causes the air between the lightning rod and the cloud to break down easily and become a conductor when the charge on the cloud reaches a certain value. In this way, the charged clouds and the lightning rods form a path, and the lightning rods are grounded. The lightning rod can guide the electric charge on the cloud layer into the earth so that it does not pose a danger to the high-rise building and ensures its safety.
What are the disadvantages of lightning rods?
Installation costs are higher, especially in larger buildings, often requiring multiple lightning rods and complex wiring costs.
Attention should be paid to maintenance and good conductivity of the lightning rod should be maintained. Once there is a bad connection or a break, the section above the break becomes an isolated conductive system. When there is a charge in the cloud, the isolated part induces a charge with a different sign from the electricity in the cloud, while the lower part induces a charge with the same sign as the electricity in the cloud.
If the upper part and the electricity in the cloud act as a discharge, a strong discharge current will A large amount of heat can only be released through the building, thus causing lightning strikes. This not only fails to protect against lightning but also attracts direct lightning strikes.
Application - Lightning Rod for Home
Most homes don’t need lightning rods because small homes are rarely affected by lightning, but if your home is tall or your area has frequent thunderstorms, installing a lightning rod can be a reassuring option.
Generally speaking, one lightning rod on the roof is enough. If there are other needs, increasing the number can also be considered.
Lightning rods for residential use are no different. Choose the appropriate device according to the actual situation and leave it to professional electricians for installation.