Why do you hear “crackling” when you take off your sweater?

At night when you take off your sweater, sometimes you will hear the “rattle” if the light is off; you can even see the flowers flashing. What is that about?
Perhaps you think, on your body, you have just experienced hundreds of “thunder” turns. That’s not sensational talk. American physicist Franklin, from 1752, used his famous kite-flying experiment to prove lightning is the phenomenon of electrical discharge in nature. Of course, the lightning discharge scale is very large, and what you experience is nothing more than “micro lightning,” which has a very small discharge scale, so you can feel nothing. But why is the body charged with electricity?

We know that atoms make all objects. The atom contains several electrons. The electron is negatively charged, the atomic nucleus is positively charged. When the positive and negative charges are equal, the outside does not exhibit electrical properties. If we use leather, rub the rubber rod, rub the glass rod with plastic, the objects that are not charged immediately carry electricity and absorb small pieces of paper. When there is continuous friction between objects, it turns out that due to the weak atomic absorption power of the atomic nucleus of different matter. The friction can make some electrons from the object weak electron attraction runs to an object with relatively strong electron attraction. As a result, the object loses a positively charged electron; the object receives a negatively charged electron. This process is called friction, generating electricity. Electricity generated by friction cannot move, called static electricity.

There are many examples of friction in life. For example, when the weather is dry, using plastic or hard rubber comb to brush the hair clean, immediately there are some electrons from the hair running to the comb, making the hair on the head positively charged, the comb negatively charged. Put the comb beside the hair, and the hair will be gently pulled into it.

We wear sweaters, working all day, making the middle of the sweater and the shirt, between the shirt and the skin constantly rubbing. Friction renders our clothes and body charged. By evening when the sweater is removed, some positive and negative charges neutralize, causing a discharge. So we immediately heard the “rattle,” saw the electric flower flashing.

You may have some concerns. The body is charged; will it get an electric shock? Don’t forget that your body’s electricity is static, there is no electricity flowing through you, so there is no problem for you. Then there is the phenomenon of electrical discharge when taking off the sweater, is there no current? Yes, but because the amount of electricity on the body is very small, only about one-millionth of a coulomb, even if the discharge time is a hundredth of a second, the amperage is only 0.1 mA, compared to the 50mA current electric shock to the people, the difference is very far.

Although the current generated by static electricity on the body does not harm our bodies, it can have other serious consequences. Sparks caused by an electric discharge can ignite the gasoline and lead to an explosion. Therefore, employees working in the gas depot must not wear plastic or terylene clothing (British synthetic fibers). Also, petrol transport vehicles must drag an iron chain “tail.” That “tail” is used to promptly transfer the accumulated charge on the vehicle to the ground.

Static electricity is also present that can be taken advantage of. Electrostatic photocopiers and laser printers use an optical method to create a picture of electrostatic precipitation first, rely on electrostatic attraction to pull up toner, and then transfer the toner onto photocopy paper seal-up pattern. Finally, heat the toner to remain solid on the paper. The Van de Graaf generator is also an electrostatic accelerator for ions, which can be used for ionizing radiation into semiconductors and in nuclear physics research.