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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Live electricity. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Electricity for beginners In wildlife, there are many processes associated with electrical phenomena. Let's consider some of them. Many flowers and leaves have the ability to close and open depending on the time and day. This is due to electrical signals, which are action potentials. Leaves can be forced to close with external electrical stimuli. In addition, many plants develop damage currents. Sections of leaves and stems are always negatively charged with respect to normal tissue. If you take a lemon or an apple and cut it, and then attach two electrodes to the peel, they will not reveal a potential difference. If one electrode is applied to the peel, and the other to the inside of the pulp, then a potential difference will appear, and the galvanometer will note the appearance of a current. The change in the potential of some plant tissues at the time of their destruction was studied by the Indian scientist Bose. In particular, he connected the outer and inner parts of the pea with a galvanometer. He heated a pea to a temperature of up to 60 ° C, while an electric potential of 0,5 V was registered. The same scientist studied a mimosa pad, which he irritated with short current pulses. When irritated, an action potential arose. The mimosa reaction was not instantaneous, but delayed by 0,1 s. In addition, another type of excitation, the so-called slow wave, appeared in the conductive pathways of mimosa, which appeared during damage. This wave bypasses the pads, reaching the stem, causing an action potential to be transmitted along the stem and causing nearby leaves to drop. Mimosa responds by moving the leaf to irritation of the pad with a current of 0,5 μA. The sensitivity of the human tongue is 10 times lower. No less interesting phenomena associated with electricity can be found in fish. The ancient Greeks were wary of meeting fish in the water, which made animals and people numb. This fish was an electric stingray and was called a torpedo. In the life of different fish, the role of electricity is different. Some of them, with the help of special organs, create powerful electrical discharges in the water. So, for example, freshwater eel creates a tension of such strength that it can repel an attack by an enemy or paralyze a victim. The electrical organs of the fish are made up of muscles that have lost their ability to contract. Muscle tissue serves as a conductor, and connective tissue serves as an insulator. Nerves from the spinal cord go to the organ. But in general, it is a small-plate structure of alternating elements. The eel has from 6000 to 10000 elements connected in series, forming a column, and about 70 columns in each organ, located along the body. In many fish (gymnarch, knife fish, gnatonemus), the head is charged positively, the tail is negative, but in electric catfish, on the contrary, the tail is positive and the head is negative. Fish use their electrical properties for both attack and defense, as well as to find prey, navigate in troubled waters, and identify dangerous opponents. There are also weakly electric fish. They do not have any electrical organs. These are ordinary fish: crucians, carps, minnows, etc. They feel the electric field and emit a weak electrical signal. First, biologists discovered the strange behavior of a small freshwater fish - the American catfish. He felt a metal stick approaching him in the water at a distance of several millimeters. The English scientist Hans Lissman enclosed metal objects in a paraffin or glass shell, lowered them into the water, but he failed to deceive the Nile catfish and the hymnarchus. The fish felt the metal. Indeed, it turned out that fish have special organs that perceive weak electric field strength. Checking the sensitivity of electroreceptors in fish, scientists conducted an experiment. They closed the aquarium with a fish with a dark cloth or paper and led a small magnet nearby through the air. The fish felt the magnetic field. Then the researchers simply moved their hands near the aquarium. And she reacted even to the weakest bioelectric field created by a human hand. Fish are no worse, and sometimes even better than the most sensitive instruments in the world, register the electric field and notice the slightest change in its intensity. Fish, as it turned out, are not only floating "galvanometers", but also floating "electric generators". They radiate an electric current into the water and create an electric field around them that is much stronger in strength than that arising around ordinary living cells. With the help of electrical signals, fish can even "talk" in a special way. Eels, for example, at the sight of food begin to generate current pulses of a certain frequency, thereby attracting their fellows. And if two fish are placed in one aquarium, the frequency of their electrical discharges immediately increases. Rival fish determine the strength of their opponent by the strength of the signals they emit. Other animals do not have such feelings. Fish live in water. Sea water is an excellent conductor. Electric waves propagate in it, without fading, for thousands of kilometers. In addition, fish have physiological features of the structure of muscles, which eventually became "living generators". The ability of fish to accumulate electrical energy makes them ideal batteries. If it were possible to understand in more detail the details of their work, there would be a revolution in technology, in terms of creating batteries. The electrolocation and underwater communication of fish has enabled the development of a system for wireless communication between a fishing vessel and a trawl. It would be appropriate to end with a statement that was written next to an ordinary glass aquarium with an electric ray, presented at the exhibition of the English Royal Society of Science in 1960. Two electrodes were lowered into the aquarium, to which a voltmeter was connected. When the fish was at rest, the voltmeter showed 0 V, while the fish moved - 400 V. The nature of this electrical phenomenon, observed long before the organization of the Royal Society of England, still cannot be unraveled by a person. The mystery of electrical phenomena in wildlife still excites the minds of scientists and requires its solution. Author: L.P. Yatsenko
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