Static electricity is a static charge. In the dry and windy autumn, people often encounter this phenomenon in their daily life: when they take off their clothes and go to bed at night, crackling sounds are often heard in the dark, and static electricity can make people feel pain. Let me introduce the main causes of static electricity.
We know that matter is composed of molecules, molecules are composed of atoms, and atoms are composed of negatively charged electrons and positively charged protons. Under normal conditions, the number of protons in an atom is the same as the number of electrons, and the positive and negative are balanced, so it is uncharged externally. However, electrons surround the atomic nucleus, and once they are out of orbit by external force, they leave the original atom and enter other atoms, so that the atom is positively charged due to the lack of electron number, and the other atoms are negatively charged due to the increase of electron number. The excess or insufficient relatively static charge on the surface of this object is called static electricity. The ways of causing static electricity usually include solid electrification, induction electrification, friction electrification, human body electrification and so on.
There are three main forms of human electrification. First, contact separation and electrification, that is, the friction between people's clothes and external substances during activities, and the contact and separation between shoes and the ground. Second, inductive charging; The third is the adsorption of charged particles. When the human body moves in the space with charged particles, the charged particles are adsorbed by the human body, making the human body charged. Some external factors have a great impact on static electricity. The main factors are human body and humidity.
Human factors
Because people are constantly moving, people's bodies are easy to carry static charges; Insulating materials such as human skin, hair and body will store a considerable amount of static charge; Because people are operating, the static electricity of human body will be transmitted (emitted) to components or equipment.
Low humidity (dry air)
Humidity has a great influence on the accumulation and dissipation of static electricity. When the humidity is low, the electrostatic potential is high; When the humidity is high, the electrostatic potential is low. This is mainly because when the humidity is high, water molecules (sometimes conductive impurities) are adsorbed on the surface of the insulating material to reduce the insulation and facilitate electrostatic leakage. Different substances are affected differently by humidity. Those with high hygroscopicity are easy to be wetted by water and are greatly affected by humidity; Moisture absorption is small, and it is also less affected by humidity. For example, the glass surface is easy to be wetted by water, while paraffin, PTFE and other substances that are not easy to be wetted by water are less affected by humidity.
Static electricity is not static electricity, but electricity that temporarily stays somewhere in the macro. When people stand up on the carpet or sofa, the human body voltage can also be more than 10000 volts, while the static electricity in the rubber and plastic film industry can be as high as 100000 volts.
Matter is made up of molecules, molecules are made up of atoms, and atoms are made up of positively charged nuclei and negatively charged electrons. Under normal conditions, the number of positive and negative charges of an atom is the same and the positive and negative charges are balanced, so it shows the phenomenon of no charge to the outside world. The phenomenon of electrons leaving the nucleus at a high speed due to the penetration of electrons into the nucleus is called the phenomenon of electrons leaving the nucleus at a high speed; B atom is negatively charged due to increasing the number of electrons, which is called anion. The reason for the unbalanced electron distribution is that the electron is separated from the orbit by an external force. This external force contains all kinds of energy (such as kinetic energy, potential energy, thermal energy, chemical energy, etc.). In daily life, any two objects of different materials contact and then separate, which can produce static electricity. When two different objects contact each other, one object will lose some charge. For example, the electron will be transferred to another object to make it positively charged, while the other object will get some remaining electrons and negatively charged. If the charge is difficult to neutralize in the process of separation, the charge will accumulate and bring static electricity to the object. Therefore, the separation of objects from other objects will bring static electricity. Usually, peeling a piece of plastic film from an object is a typical "contact separation" electrification. In daily life, the static electricity generated by taking off clothes is also "contact separation" electrification. Solids, liquids and even gases will be electrostatic due to contact separation. This is because gas is also composed of molecules and atoms. When air flows, molecules and atoms will also be "contact separated" and electrified. We all know friction electrification, but we seldom hear contact electrification. In essence, triboelectrification is a process of contact and separation, resulting in the imbalance of positive and negative charges. Friction is a process of continuous contact and separation. Therefore, friction electrification is essentially contact separation electrification. In daily life, all kinds of objects may generate static electricity due to movement or friction [1]. Another common electrification is inductive electrification. When a charged object approaches an uncharged object, negative and positive charges will be induced at both ends of the uncharged conductor respectively.
There are many hazards of static electricity, the first of which comes from the interaction of charged bodies. When the aircraft body rubs with air, moisture, dust and other particles, it will make the aircraft charged. If no measures are taken, it will seriously interfere with the normal operation of the aircraft radio equipment and make the aircraft deaf and blind; In the printing factory, the static electricity between the paper sheets will make the paper sheets bonded together and difficult to separate, which brings trouble to the printing; In the pharmaceutical factory. Because the static electricity attracts dust, the drug will not reach the standard purity; When playing TV, the static electricity on the screen surface is easy to absorb dust and oil, forming a layer of dust film, reducing the clarity and brightness of the image; The dust that is common on blended clothes and is not easy to pat off is also the ghost of static electricity. The second major hazard of static electricity is the possibility of explosion due to the ignition of some flammable objects by electrostatic sparks. In the dark night, when people take off nylon and wool clothes, they will make sparks and "Baba" sound, which is basically harmless to the human body. But on the operating table, the electric spark will cause the explosion of anesthetic and hurt doctors and patients; In the coal mine, it will cause gas explosion, which will lead to the death and injury of workers and the scrapping of the mine.
In short, electrostatic hazards are caused by the use of electricity and electrostatic sparks. The most serious electrostatic discharge in electrostatic hazards causes the fire and explosion of combustibles. It is often said that the measures to prevent the occurrence of static electricity are generally to reduce the flow rate and flow, transform the process links with strong electrification, and adopt equipment and materials with less electrification. The simplest and most reliable way is to ground the equipment with wires, which can lead the charge to the earth and avoid the accumulation of static electricity. Careful passengers will probably find; Discharge brushes are installed at the wing tips on both sides of the aircraft and the tail of the aircraft. When the aircraft lands, in order to prevent passengers from being electrocuted when flying down, special grounding tires or grounding wires are mostly used on the aircraft landing gear; To release the static charge generated by the aircraft in the air.
We often see an iron chain at the end of the tank car, which is the grounding wire of the car. Properly increase the humidity of the working environment and let the charge release at any time, which can also effectively eliminate static electricity. This is the reason why it is not easy to do static electricity test in wet weather. The antistatic agent studied by researchers can well eliminate the static electricity inside the insulator. However, everything has two sides. For the hidden troublemaker of static electricity. As long as we understand its temper and develop its strengths and avoid its weaknesses, we can also make it serve mankind. For example, electrostatic printing, electrostatic spraying, electrostatic flocking, electrostatic dust removal and port electric separation technology have been widely used in industrial production and life. Static electricity has also begun to play an important role in desalinating seawater, spraying pesticides, artificial rainfall, low-temperature freezing and many other aspects. Even static electricity devices such as electrostatic feeders are installed on Zizhou spacecraft.