# Principles of current, charge, material and light properties

## Electricity, light energy and wind energy are in many ways closely linked to one source, which is the atom.

①Current
Electric current originates from the flow of free electrons in the material. In atoms, the electrons located in the valence electron layer are less attracted by the nucleus. When these electrons have gained enough energy, they can easily get rid of the bondage of the orbital and become free electrons. In Figure 1, an electron from one atom knocks an electron in another atom out of the orbit, and the electron that has been knocked out of the orbit becomes a free electron.

When an electron leaves its valence electron layer and gains “free”, it can hit another electron and hit the valence electron layer. The first electron usually fills the “holes” left by the second electron. This process continues from one atom to another, allowing different electrons to be “free.” The free electrons flowing in the wire always try to go to the power supply terminal that lacks electrons—that is, flow from the negative pole of the power supply to the positive pole of the power supply through an external circuit. For example, electrons flow from the negative electrode of the battery through a circuit back to the positive electrode of the battery. This movement of electrons in the wire is the current (see Figure 2).

② Law of conservation of electric charge
It can be seen from Figure 3 that charged objects attract or repel each other. This effect stems from the law of charge, that is, charges of opposite sex attract each other and similar charges repel each other. Electrons are negatively charged. When a piece of material has excess electrons, there is a net negative charge; when a piece of material lacks electrons, there is a net positive charge. A material with a net negative charge is more “negative” than a material with a net positive charge.

Now take a look at the power supply in Figure 2. Power sources such as batteries have positive and negative terminals, the negative terminal has excess electrons, and the positive terminal lacks electrons. Therefore, when an electric bulb is connected to the battery terminal, the electrons in the wire are pushed out (repelled) by the negative electrode (-), and pulled (attracted) by the positive electrode (+), so that the electrons flow through the bulb and point them. Bright. Note that both the positive and negative electrodes have electrons, but the left terminal has more electrons than the right end, so the left end is “negative” than the right end. The right terminal has fewer electrons, so it is “positive” than the left terminal.

③Electrical materials
According to the number of free electrons contained, the materials used in the electrical field can be divided into three categories:
(1) Conductor A material that contains a large amount of free electrons, which can make the current flow smoothly. Copper and aluminum are common conductors.
(2) Nano edge body: A material that contains a very small amount of free electrons and does not allow current to pass. Plastic and rubber are common insulators.
(3) The number of free electrons in semiconductor materials is less than that of conductors, but more than that of insulators. Silicon and germanium are common semiconductor materials that can be used to make transistors and photovoltaic cells.

④Crystal material
The element table shown in Figure 4 lists the characteristics of individual atoms, but atoms can be combined with each other to form different structures by sharing electricity. For example, atoms can be combined into a solid, pure material. Take silicon as the side. Each independent silicon atom has 14 electrons, 4 of which are located in the valence electron layer. Under certain conditions, silicon atoms will also combine with each other, so that each atom’s valence electron layer has 8 electrons. This structure is called a crystal. Figure 5 clearly shows this structure.