HOW DID SUCH A SCIENCE AS ELECTRONICS APPEAR?
The purpose of this lesson is to give an idea of electronics as a science — a branch that, both in the past and today, fills its niche in almost all areas of the national economy, education, and technology. In this lesson, you will also get an idea of the structure of matter and electrically charged particles. We will also touch upon the structure of the atom, the concept of electricity, and the electrification of bodies. At the end of the lesson, there will be a small practical assignment.
As the large encyclopedic dictionary tells us, ELECTRONICS is the science of the interaction of charged particles (electrons, ions) with electromagnetic fields and the methods of creating electronic devices and equipment (vacuum, gas-discharge, semiconductor), used mainly for the transmission, processing, and storage of information. Electronics as a science emerged in the early 20th century; initially, it was mainly vacuum electronics that developed, and vacuum-tube devices were created on its basis. Since the early 1950s, solid-state electronics (primarily semiconductor) has been intensively developing; since the early 1960s, one of its most promising areas — microelectronics — emerged. After the creation of the quantum generator, the development of quantum electronics began. Electronic devices and equipment are used in communication systems, automation, computing, measuring technology, etc. And RADIO ELECTRONICS is a collective name for a number of areas of science and technology related to the transmission and transformation of information based on the use of radio-frequency electromagnetic oscillations and waves; the main ones are radio engineering and electronics. The methods and tools of radio electronics are applied in most areas of modern technology and science. In other words, there were two related sciences, radio engineering and electronics, and as a result of their merger, radio electronics emerged. It is enough to remember at least this. And, of course, we need to define such concepts as amateur radio (radio amateur) and beginner radio amateur, since my lessons are addressed specifically to this category of people.
And so, the entire population of the globe can be conditionally divided into two groups: those who have a hobby and those who do not. This word, which came into the Russian language relatively long ago (from the English "hobby"), translates as a favorite pastime or passion. Hobbies can be very diverse. These include all kinds of collecting, fishing, sports, tourism, learning foreign languages, amateur construction, and much, much more. Still, there is one hobby that allows you to combine various hobby directions together, either giving them all equal attention or focusing mainly on one specific type. This hobby is not just a way to spend leisure time interestingly. It allows you to acquire valuable practical skills and knowledge in the field of electrical and radio engineering; the name of this hobby is amateur radio. Hundreds of thousands of people around the world are engaged in amateur radio. The youngest representatives of the amateur radio army are under ten years old, and the oldest are over eighty. What attracts such a large army of people who are so different from each other to amateur radio? The fact that, as already mentioned, amateur radio is diverse, and everyone finds something most attractive in it. Do you like to build and construct? Radio amateurs, as a rule, design their electronic devices themselves, sometimes creating constructs that are on par with the best industrial models.
We have figured out what radio engineering, radio electronics, and amateur radio are. Let's move on to a detailed study of the subject.
We will certainly touch upon the topics of various experiments and discoveries in the following lessons, but now I would like to immediately draw your attention to electrical safety rules, as we will be dealing with electric current, and this is unsafe for your health. This is certainly not the most interesting section, but health is above all. Also in this section of the lessons, I will tell you what tools, devices, and materials we will need to successfully master radio electronics and the practical side of our classes. So, let's begin!!!
STRUCTURE OF MATTER, THE ATOM
Legend attributes the discovery of electrical phenomena to the wisest of ancient Greek thinkers, Thales, who lived more than two millennia ago. Even in those times, in the vicinity of the ancient Greek city of Magnesia, people found pebbles on the seashore that attracted small metal objects. They were named magnets after the name of this city. Thales also found other equally mysterious, beautiful, and light pebbles. They did not attract metal objects, but if rubbed with a woolen cloth, fluff and light pieces of dry wood or grass would stick to them. This is amber. The ancient Greeks called amber electron. This is where the word electricity comes from.
The electrification of bodies by friction can be observed by rubbing a plastic comb with a woolen cloth and bringing it close to small pieces of thin paper: they will instantly rush to the electrified comb. Hair is also attracted to the comb, and sometimes miniature sparks, or micro-discharges, even appear. Although this looks like a magic trick, there is nothing mysterious here: amber, plastic, or glass rubbed with wool acquire an electrical charge, thanks to which, like a magnet, they attract pieces of paper or hairs. But neither the ancient Greeks nor other thinkers and philosophers could explain this property of amber for many centuries.
In the middle of the 17th century in Holland, at the University of Leiden, scientists found a way to accumulate electrical charges. Such a collector of electricity was the Leyden jar (named after the university) — a glass vessel whose walls are pasted over with lead foil on the outside and inside. A Leyden jar, connected by its plates to an electrical machine, could accumulate and retain a significant amount of electricity for a long time. If its plates were connected by a piece of thick wire, a strong spark flashed at the point of contact, and the accumulated electrical charge instantly disappeared. If the plates of the charged device were connected with a thin wire, it quickly heated up, flashed, and melted, i.e., burned out, as we often say now. The conclusion could only be one: an electric current flows through the wire, the source of which is the electrically charged Leyden jar.
Today we call such devices electrical capacitors (the word capacitor means a condenser), and their non-connecting foil strips are called capacitor plates. A more perfect, and most importantly, almost continuous source of electric current was invented at the end of the 18th century by the Italian physicist Alessandro Volta. Between small discs of copper and zinc, he placed a cloth soaked in an acid solution. While the pad is moist, a chemical reaction occurs between the discs and the solution, creating a weak electric current in the conductor connecting the discs. By connecting pairs of discs into a battery, a significant electric current could be obtained. Such batteries were called Voltaic piles. They laid the foundation for electrical engineering.
We call a similar current source a galvanic cell after Luigi Galvani, who discovered the phenomenon of electric current, and cells connected in parallel or in series are called galvanic cell batteries. Practice has shown that there are two types of electricity. One of them, corresponding to the electrical charge of a copper plate, began to be conditionally considered positive, and the second, corresponding to the charge of a zinc plate, negative. Accordingly, the first plate — the pole of the current source — began to be called positive and denoted by the + sign, and the second pole — negative and denoted by the - sign. It was also conditionally assumed that the current flows from the positive to the negative pole of a cell or battery. Here I have to jump a little ahead to answer a question that you probably already have: what is an electric current?
Electric current is the ordered movement of electrical charges. To understand this phenomenon of nature, we will have to mentally penetrate the micro-world of matter.
Matter is everything that makes up all objects and bodies existing in nature: solid, liquid, gaseous. All of them are formed from atoms. Atoms are extremely small. The unit of length, the millimeter, is completely unsuitable for measuring them, as it is too large. Neither a thousandth of a millimeter (a micron) nor a millimicron, which is a thousand times smaller than a micron, is suitable for such measurements. Only a tenth of a millimicron works. The diameter of atoms of various substances ranges from 0.1 to 0.4 nm (10^-10 m = 0.1 nm). In other words, from 25 to 100 million atoms can freely fit on a section 1 cm long. Previously, it was assumed that an atom is the smallest indivisible particle of matter. The word atom itself means indivisible. But later scientists learned that the atom also consists of smaller particles. In the center of an atom of any substance is a nucleus, the size of which is approximately 100 thousand times smaller than the size of the atom itself. And then it turned out that the nucleus also consists of even smaller particles, which were called protons and neutrons. Today, scientists successfully destroy, or, as they say, split atomic nuclei and extract the huge energy hidden in them — atomic energy. At nuclear power plants, this energy is converted into the energy of electric current. Atomic energy propels marine vessels, such as icebreakers and submarines. An atom can be represented as a world of microscopic particles rotating around their axis and around one another. And in the center of this micro-world is a dense, massive nucleus, around which much smaller particles called electrons orbit. Electrons form the shell of the atom.
What are the sizes of electrons? Extremely small. If a pinhead were mentally enlarged to the size of our planet Earth, each atom of the metal from which the pin is made would increase to the size of a sphere 1 meter in diameter. And in the center of such a fantastically enlarged atom, we would see its nucleus — a ball the size of a typographical dot, around which barely visible dust motes — electrons — would rotate.
If you want to know the size of an electron, divide the number 3 by a one with 12 zeros. You will get the approximate diameter of an electron, expressed in millimeters. Electrons are often called particles. However, this should not be understood in the sense that an electron is something like a solid lump or a ball. According to modern concepts, electrons can be likened to clouds surrounding the atomic nucleus and orbiting it. The electron is sort of smeared over the shell of the atom. However, for the clarity of explaining physical natural phenomena, electrons are often conditionally, somewhat symbolically, depicted in drawings as balls revolving around the atomic nucleus like artificial satellites around the Earth.
I think this drawing should remind you of something. For those who guessed it — well done; for those who didn't, I will give you a hint: this is exactly the logo of my page for beginners. Now you understand why such a logo was chosen. It is quite symbolic. Let's continue...
In the atom of each chemical element, the number of electrons is strictly defined, but it differs for different chemical elements. The simplest design belongs to the hydrogen gas atom — its shell contains only one electron. The shell of a helium atom (this gas fills tubes for red-glowing signs and advertisements) has two electrons. Atoms of other chemical elements contain more electrons, and their electron shells are multi-layered. An oxygen atom, for example, has eight electrons arranged in two layers: two electrons move in the first, inner layer closest to the nucleus, and six in the second, outer layer. Each iron atom has 26 electrons, and each copper atom has 29. Iron and copper atoms have four-layered electron shells: two electrons in the first layer, eight in the second and third, and all the rest in the outer, fourth layer. Electrons located in the outer layer of the atom's shell are called valence electrons. Remember this: valence. We will recall valence electrons more than once, especially when we talk about semiconductor devices. You can find out about the number of electrons in the atoms of various substances from the periodic table of chemical elements compiled by the great Russian scientist Dmitri Ivanovich Mendeleev. For now, it is desirable to remember: the number of protons in the nucleus of an atom is always equal to the number of electrons that must be in the electron shell of the atom of a given substance. Each proton of the atomic nucleus carries a positive (+) electrical charge, and each electron of the atomic shell carries a negative (-) electrical charge equal to the proton's charge. Neutrons, which are part of the atomic nucleus, carry no charge.
You have certainly played with magnets more than once. After all, only the existence of an invisible magnetic field penetrating the space around its poles can explain the phenomenon of its attraction to iron objects. Thanks to this field, you can, for example, make a nail stand vertically on a table without touching it with the magnet. But what if you try to connect two magnets with the same poles? They will repel each other! And with opposite poles? In this case, the poles of the magnets will attract and stick to each other. Electrical charges behave in a similar way: like charges repel each other, and opposite charges attract. Experiment with magnets to solidify your knowledge through practice.
If electrons have a negative charge, opposite in sign to the charge of protons, this means that electrical forces are constantly acting between them in the atom, keeping the electrons near their nucleus. "But why don't the electrons fall into the nucleus?" you may ask. Because they orbit the nucleus at a tremendous speed. The Moon does not fall onto the Earth, although the Earth attracts its eternal satellite. Since the total negative charge of all electrons in an atom is equal to the total positive charge of all protons, the atom outwardly shows no electrical properties. Such an atom is said to be electrically neutral. This intra-atomic property can be compared to this phenomenon: if you put an equal number of penny coins on two pans of a scale, the scale will be in balance. Valence electrons, being at the greatest distance from the nucleus, are held by the nucleus more weakly than those closer to it. Under various external influences, for example, upon heating, rubbing, or under the influence of light, the valence electrons of some substances can leave their atoms and even the boundaries of the body they were part of. Such electrons that have left their atoms are called free electrons. But what happens to an atom that has lost one or more electrons? Its internal electrical balance is disturbed. The positive charge of the nucleus begins to predominate, and the atom as a whole becomes positive. Such an atom is called a positive ion. In this case, it, like a magnet, tends to attract free electrons that happen to be nearby or take them from neighboring atoms to make up for the loss and become electrically neutral again. And what if an extra electron appears in the electron shell of an atom? Such an atom will exhibit the properties of a negative charge. This will be a negative ion. At the first opportunity, it will expel the extra electron to become electrically neutral again. Related atoms or atoms of different chemical elements combine to form molecules. In such a molecule, both electrons move around two atomic nuclei. Here it is no longer possible to distinguish which electron belongs to which of the two atoms. If you combine two hydrogen atoms with one oxygen atom, you get a water molecule. All bodies are built on the basis of molecules. Paper, for example, is woven from cellulose molecules, which include atoms of hydrogen, oxygen, and carbon. A molecule, like an atom, is electrically neutral if the total number of electrons in it is equal to the total number of protons located in its atomic nuclei. If the number of electrons in a molecule is less than the number of protons, the molecule will carry a positive charge, and if it is greater than the number of protons, a negative charge. If some of the electrons from the atoms or molecules of one body are transferred in some way to another, then electrical forces will arise around these bodies and in the space between them, or, as they say, an electrical field will be created.
Here is the answer to the secret of the comb rubbed with a woolen cloth or silk! When rubbed against wool, the comb gives it a portion of its electrical charges, as a result of which it becomes electrified itself. An electric field arises around the electrified comb, due to which it acquires the ability to attract light objects. An electric field also acts between two parts of the same body, for example, in a piece of metal, if one part has an excess of electrons and the other has a shortage. Conditions arise for the movement of excess electrons to the part of the body where they are lacking.
The electrical charge of one electron is negligibly small. But if there are many electrons and if they can be made to move inside a body in one direction, forming a flow of negative charges, you will get what was mentioned above as an electric current.
That's all you need to master in this lesson. The lesson turned out to be quite comprehensive, but the practical part is very easy. From this lesson, you need to remember the basic concepts (electrical engineering, electronics) and definitions (structure of matter and the atom). You will repeatedly recall and encounter everything discussed in this lesson, so if you have decided to dedicate yourself to radio electronics, try to grasp the essence of what has been said.
PRACTICAL WORK
Your first practical work will consist of repeating the experiments with the electrification of bodies and the phenomenon of magnetism (with magnets) described in this lesson. As you have guessed, for this we will need a comb, finely chopped pieces of paper, and two small magnets. And then, following the lesson, start your experiments. And remember one wise phrase: theory without practice is dead, and concerning radio electronics, this is an absolute rule; here, more than anywhere else, experiments are very important.
Moving on to the next lesson!
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