How many volts of static electricity can cause sparks to fly from your fingers? | Science Gallery

Is this scene familiar to everyone?

This is one of the permanent projects in many science and technology museums.

Touching it can make people instantly "furious".

Tell Pangke loudly, what is the principle of this exhibit?

Static electricity

In our daily lives, we often deal with static electricity: when we comb our hair, it sometimes inexplicably "floats" up, becoming more and more tangled, accompanied by crackling sounds.

When you touch the handle, you will suddenly feel a needle-like pain in your fingertips as soon as your fingers touch it.

I want to wear beautiful skirts in winter, but I find that they are all stuck to my legs~

Since static electricity is everywhere, what exactly is static electricity?

How is static electricity generated?

As we all know, atoms are the basis of everything in the world. They are composed of electrons, neutrons and protons, and the generation of static electricity is related to the "electrons" among them.

Electrons are a kind of basic particles that make up matter. They have very small mass and carry a certain electric charge. There are only two kinds of electric charges in nature: positive charge and negative charge. Charges of the same kind attract each other, and charges of different kinds repel each other.

Static electricity is formed when electric charges gather on the surface of an object. Since electric charges are divided into positive and negative charges, static electricity is also divided into positive and negative static electricity: when positive charges gather on an object, positive static electricity is formed, and when negative charges gather on an object, negative static electricity is formed. But whether it is positive static electricity or negative static electricity, when an object with static electricity contacts an object with zero potential or an object with a potential difference with it, charge transfer will occur, and the static electricity phenomenon we always see in our daily life will appear.

Static electricity generated on a conductor can disappear quickly because it can flow, but on some insulators, it will remain relatively still. When it reaches a certain level, it will produce a discharge phenomenon, usually accompanied by a sound and sparks. Back to the beginning of the article, how does the static electricity ball work? It turns out that the metal ball has a large amount of charge. When a person stands on an insulating platform and touches it with his hand, the body will carry the same charge. Due to the repulsion of the same charge, each hair also repel each other, thus forming the "angry hair" phenomenon.

The hazards of static electricity

Although static electricity is small, it can be very powerful sometimes. In late autumn and winter and spring, the static voltage generated when people walk on a blanket can exceed 3,000 volts; when people take off pure polyester clothes, a high voltage of 50,000 to 100,000 volts can be generated instantly; when people wear chemical fiber clothes and sit on the sofa and suddenly stand up, the static voltage of the human body can be as high as 10,000 volts or more when the friction and contact between the clothes and the sofa cushion separate. When the static voltage reaches 2,000 volts, the fingers will feel it; when it exceeds 3,000 volts, sparks will appear and the fingers will feel tingling; when it exceeds 7,000 volts, people will feel an electric shock. Although the voltage of static electricity seems high, because its charge is very small, the corresponding current when it is discharged is also very small, so it generally does not cause direct harm to the human body.

However, everything has two sides. Although static electricity seems harmless, it is actually the fuse of some accidents. In 1969, several oil tankers exploded and caught fire due to static electricity; in 1970, two Boeing aircraft had fuel tank explosions due to static electricity in the fuel; even on the operating table, there have been cases where static electricity detonated the anesthetic ether, resulting in serious casualties. In daily life, there are also many reports of accidents caused by static electricity.

Static electricity sparks generated when moving plastic barrels caused gasoline vapor to explode and spread to cause disasters

A gas station exploded due to static electricity igniting dangerous materials during a filter press test.

The accumulated static charge discharge ignited the explosive gas formed by the mixture of ethanol vapor and air around the extraction tank, causing an explosion.

In addition, experts also remind everyone that the harm of static electricity to the human body cannot be ignored, especially for the elderly and patients. Static electricity can aggravate their condition. Excessive static electricity often makes people anxious, have headaches, chest tightness, difficulty breathing, coughs, etc.

Since static electricity is so dangerous, is there any way to prevent the harm of static electricity? In life, we can eliminate the trouble of static electricity through a humidifier. Indoors, use an air humidifier to increase the humidity of the air, which can effectively eliminate static electricity. If you are outdoors, before touching a metal object, you can touch the wall with your hand to transfer the static electricity on your body to the earth, which can effectively alleviate the harm caused by static electricity.

For industrial production, preventing static electricity is even more important. Whether it is neutralizing static electricity, grounding and conducting current, or letting it dissipate on its own, the most important thing is to strengthen the awareness of prevention and do a good job of security work in all links, so as to effectively prevent the occurrence of danger.

The role of static electricity

Static electricity is not completely useless. As long as it is used in the right place, it can still play its role. Electrostatic dust collector uses the effect of static electricity to absorb dust particles suspended in the gas, thereby removing them. Electrostatic copying and printing technology uses the static latent image left during charge transfer, which is revealed by a certain method to achieve copying and printing.

Static electricity can be used to purify water. The conductivity of a substance is directly related to the amount of free charge it contains, but pure water after distillation is almost non-conductive, which means that the conductivity of ordinary water is not provided by water molecules, but by other substances dissolved in water, and this substance is inorganic salt. The conductivity of seawater is stronger than that of ordinary water because of the high content of inorganic salts. Based on this characteristic, scientists invented the electrostatic dialysis method, which uses ion exchange membranes and static electricity to dialyze inorganic salts containing electrons in water to obtain pure water.

In addition, the electrostatic printing technology based on the principle of electrostatic imaging can make the sequentially arranged charges as electrostatic latent images, precipitate on the surface or body of the material, and then develop and transfer them into a form visible to the human eye. This technology is also very common in daily life.

These various technologies all reflect the effective application of static electricity in life in different aspects. So far, the exploration of static electricity has gradually developed into a science - electrostatics, which witnesses the progress of human civilization and also plays its role in enabling humans to live a better life.

What interesting stories do you have about static electricity in your life? Welcome to leave a message in the comment area! After all, static electricity is really more complicated than we can see!

Creative team: China Science and Technology Museum New Media Team

Review expert: Li Yongle, physics teacher at Beijing Renmin University High School, well-known science blogger

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