1886, Hertz successfully proved that two electric oscillations can cause * * * oscillations, which further proved the existence of electromagnetic oscillations. 1887165438+1October 5th, he summed up his experimental results, wrote them in a paper entitled "On the Induction Phenomenon Caused by Electrical Process in Insulators" and sent them to his tutor Helmholtz.
Let's use the topic of Hertz's paper to talk about the insulator he mentioned. The so-called insulator is a non-conductive substance. In our daily life, we know that when a metal wire is connected to both ends of the power supply, there will be current flowing in the wire, which is the basis of using electrical appliances in practical applications. We can use wires to bring electricity from distant power plants to homes and drive televisions, refrigerators and other electrical appliances to work. A metal wire is a conductor. It can conduct electricity.
There are many substances that can be used as conductors. Besides metal materials, the earth, salt water and human body are all conductors, and the decomposed air is also a conductor.
In addition to conductors, there are other completely non-conductive substances, such as bakelite, dry sticks, ceramics, dry air and so on. They are all insulators and can't conduct electricity. We can use them to isolate conductors, such as wrapping a layer of rubber on two wires that are close together, which can not only prevent the two wires from touching each other and causing short circuit, but also prevent us from accidentally touching the wires and getting an electric shock. Air is also an insulator, so we don't have to worry that current will pass through the air to our bodies and get an electric shock.
Conductor and insulator can also be transformed into each other: for example, dry air is an insulator, but when the electric field is greater than 30 kV/cm, the air will be broken down and ionized, thus becoming a conductive conductor. Another example is that saline solution can conduct electricity, but after crystallization, salt becomes an insulator and has no conductivity.
After understanding the properties of conductors and insulators, let's look at the electric shock of human body. Both the human body and the earth are conductors, which can conduct current. Therefore, when the human hand is in contact with the charged conductor, the current will flow to the ground through the human body, forming a loop of conductor-human body-earth. When current flows through the human body, it has a strong adverse effect on the organs and tissues of the human body, such as the heart and brain. When the current reaches a certain value, the heart and brain will lose their working functions, leading to human death, so never "test electricity with your own body"!