If you often see large trucks coming and going, you will find a very interesting phenomenon. Some trucks are very strange behind, dragging a long iron chain. This iron chain is quite promising, and its role is to guide static electricity. When it comes to static electricity, many people are both familiar and unfamiliar. Static electricity is relative to electric current. There are many reasons for static electricity. For example, simple friction can cause static electricity. , There will be obvious fire light, and the hair is also erected. This kind of static electricity is large or small, the larger one may reach tens of thousands of volts, but the harm to people is relatively small. Because although the voltage is high, the current is very small and the duration is extremely short. At most, people are electrified for a short time, and there is no great harm. For example, they may be charged when they hold the door handle. , But when you hold it again, there is no current after the current has been released. Static electricity is also generated on cars. The static electricity of cars covers the surface of the car body and may also reach people, but more importantly, it may affect driving safety. Some cars may leak oil. Gasoline is in a confined space. If there is static electricity at this time, the vehicle will be ignited. The iron chain of a large truck is actually used to guide static electricity to the ground, but it is more professional. It is better to use copper wire to conduct electricity.