Tsar - electrophore

In the summer of 1814 Napoleon’s winner All-Russian Emperor Alexander the First visited the Dutch city of Haarlem. The distinguished guest was invited to the local academy. Here, as the historiographer wrote, "The large electric machine first of all attracted the attention of His Majesty." Made in 1784. the car really made a big impression. Two glass disks with a diameter of a person’s height rotated on a common axis by the effort of four people. Friction electricity (triboelectricity) was supplied to charge the battery of two-Leiden cans, capacitors of that time. Sparks from them reached a length of more than half a meter, which the emperor was convinced of.

His reaction to this Central European miracle of technology was more than restrained. From childhood, Alexander was familiar with an even larger machine, and it gave more of these sparks. It was made. even earlier in 1777. in his homeland in St. Petersburg, it was simpler, safer and required less servants than the Dutch. Empress Catherine II in the presence of her grandchildren entertained herself with the help of this machine by electrical experiments in Tsarskoye Selo. Then she, as a rare exhibit, was transferred to the St. Petersburg Kunstkamera, then, by some order, she was taken out of there and her traces were lost.

Alexander was shown the technique of the day before yesterday. The principle of generating electricity through friction has not been applied for more than 200 years, while the idea underlying the domestic machine is still used in modern laboratories of schools and universities in the world. This principle - electrostatic induction - was discovered and first described in Russia by the Russian academician, whose name few people know, and this is unfair. I would like to remind about this to the current generation.

Why did you need a giant car?

Descriptions of works produced in St. Petersburg on a giant machine were not found. It is known that in the same years in the Instrument Chamber of the Academy of Sciences on Vasilievsky Island electric generators were manufactured from "pocket" generators for entertainment and self-treatment in the family circle, to serial ones for physical laboratories of scientists. Why did they make an expensive monster car? Can I answer this question?

This is what our wanted list led to.

In 1769 in the Italian city of Brescia, lightning struck a church, in the cellars of which about 100 tons of gunpowder were stored. The explosion that followed the blow destroyed part of the city and thousands of its inhabitants. Given this widely known case, the British government turned to scientists from its academy to recommend reliable lightning protection for its powder depots. For reasons of the Royal Society of London, among whose members there was also an American lightning rod inventor B. Franklin, a lightning protection installation was proposed and carried out in warehouses in Perflit in England.

And now, with the help of modern knowledge, one cannot give a 100% guarantee of the protection of structures with the help of lightning rods (more correctly lightning rods). And ironically in 1772. the lightning rod installed in accordance with all the rules did not protect the warehouses from lightning. She “slipped” from the protective pin, but acted weak and the warehouse did not explode. This case made a lot of noise, including in Russia.

Here in St. Petersburg for 15 years the bell tower of the Peter and Paul Cathedral has been restored, which burned down after a lightning strike in 1756. When in 1772 The main repair of the bell tower spire, led by the restoration architect A. Dyakov, was completed, he turned to the local academy with a recommendation for protection, “so that lightning would not cause a spitz to burn”. January 25, 1773 The Academy Conference instructed professors Epinus, Kraft and Euler to express their views on how to install this protection.According to documents, it is known that in February professor of physics VL Kraft turned to the leadership of the academy with a request “to release one of the electric machines from the Instrument Chamber to the physics office”. Apparently for experiments ..

It is clear that Kraft had to give builders specific data: on the materials of the conductors, their diameter, material and height of the air terminal, etc. It is now known that lightning currents reach hundreds of amperes, and the charge potential of clouds is millions of volts. But then there were no volts or amperes, there was only one way to create a process model, obtain data, and extrapolate them to thunderstorm processes. Moreover, the accuracy of the data obtained would be the higher, the more electric a machine could implement a more similar to a real thunderstorm. An ordinary machine was no good: it could not melt a copper wire one millimeter thick. It was necessary to find a way out.

Russian academics sent a request to London, but even there they knew little about the requested problems. Although they themselves experimented by creating an “artificial cloud” of more than 50 meters in length and half a meter in width. The results they received were contradictory. The triboelectric machine was approaching its finale. To create high potentials, it is impossible to make glass disks with a diameter of, for example, five meters. The centrifugal force in an accident will surely turn them into thousands of fragments dangerous for experimenters. It was necessary to create some other high-voltage source of electricity for experiments.

Such a case appeared in 1776, when an electric generator was invented, which was completely different from the existing ones, but which generated electric charges in parameters even higher than a friction machine. The design was simple, so for the manufacture it was dispensed by its specialists. (Fig. 1) The experiments were performed. And on May 8, 1777. the architect Dyakov informed the Academy of Sciences about the completion of work on the lightning rod of the spire. And now the spire with a height of 122.5 meters stands reliably protected to date. But, if Americans, British and Germans know the names of their heroes in the fight against lightning, then in Russian textbooks on the history of science it can be read that VL Kraft “didn’t show anything special”, or that “physics as such, especially experimental, Kraft was not at all interested. ” And this is more than fair.

Fig. 1 Large Electrophore Kraft

3Above know-how.

June 10, 1775 the Italian physicist A. Volta announced his invention of a new source of electricity: “I present to you a body that, being electrified only once, never loses its electricity, stubbornly maintaining the strength of its action.” The author called this device the words “elettroforo perpetuo”, which could be translated as “electricity flowing forever”. The device was simple before primitivism. Its name in physical terminology was reduced to the word "electrophore", but the success of its application was overwhelming. Now, in order to receive electric charges in large quantities, it was not necessary to use the services of existing electric machines.

Volta did not consider himself the sole inventor of the device. Like every great scientist, he honored the merits of his predecessors. Here are his words: "Epinus and Wilke anticipated this idea and discovered the phenomenon, although they did not construct the finished device." What kind of anticipation is it? And the surname Epinus is found in this text for the second time. And this is no accident.

Professor of the University of Rostock F. Epinus and his student I. Wilke in electricity discovery is a phenomenon that is now called electric induction. The meaning of the discovery can be explained as follows: every body that is placed in an electric field itself becomes electric. Later, Epinus will be invited to Russia from 1757. he will become a member of the St. Petersburg Academy of Sciences. Here he will live until the end of his life, and here he will write his main work of life - "Experience in the theory of electricity and magnetism."It was published in St. Petersburg in 1759. and became very popular among physicists. I got acquainted with this work and A. Volta. He drew particular attention to the experience of the St. Petersburg academician, which we will reproduce below.

On two glass glasses A and B, a metal bar C is installed in a length of half a meter. At the ends of this bar, two other block weights 1 and 2 are placed (Fig. 2). If you bring (without touching) the grated wax stick from the side of the first weight, you can make sure when removing the small weights that they are charged. The first is positive, the second is negative electricity. Moreover, such an operation without rubbing more wax sticks can be done as many times as you like. The sealing wax did not decrease. In principle, a machine for charging bodies with electricity was ready .. It was possible instead of weights to put on a bar any bodies to be electrified and to electrify them. Why not a perpetual motion machine?

It was a prototype of Volta's electrophore, the mechanism of which is very simple to explain to contemporaries. Grated sealing wax is charged negatively. It creates an electric field that acts on the free electrons of a metal bar. Having a negative charge, they are redistributed in the bar in such a way that they accumulate in the weight 2 and remain in deficit in the weight 1. The potential difference arises at the ends of the bar. She can be disposed of at will. The genius of Volta was needed to use this phenomenon in practice and even, moreover, to reduce the meager props in the installation of Epinus. Volta does not use weights at all. Just at the moment of bringing the wax, for a second, he touches the end of the bar opposite the wax with his finger. It is clear that excess electrons flowed through the physicist’s body into the “earth”. Now, when the sealing wax was removed, the whole bar turned out to be charged with positive electricity. On this principle, it was already possible to create an electric machine more convenient than friction machines. But not only this was the advantage of the new car.

It turns out that an electrophore machine is capable of not only acquiring a charge, but also of increasing its electrical potential many times over. And Volta took advantage of this property when he proved the identity of electricity, obtained in a galvanic cell and electricity generated by friction, as well as the lightning charge of the cloud. All these charges turned out to be of exactly the same nature. And it was proved by electrophore.

How did the giant electrophore work?

An oval, tin-covered huge "frying pan" with an area of ​​about four square meters (!!!) was filled with a frozen melt of resin and wax. She lay at the base of the electrophore. On it, on racks more than two meters high, on ropes passed through the blocks, another disc-frying pan hung, a little smaller. The dimensions of the entire machine were 3 x 2.5 x 1.5 meters. (Fig. 1). Forgive the medieval artist graphic flaws. Descriptive geometry that allows you to depict three-dimensional drawings on a plane will appear only in 1799.

We specifically simplified the drawing to understand the principle of the machine. (Fig. 3) A pair of disc pans, insulated with silk ropes from each other, are an air condenser of variable capacity. Recall that the capacitance of a capacitor is inversely proportional to the distance between the plates. The smaller the distance, the greater the capacity and vice versa. The experimenter's capacity was changed by raising and lowering a suspended pan. To remove charges, a copper ball B was soldered to the upper part of the moving pan, for the lower A.

The work of the electrophore began with the excitation of a charge in the lower "pan". This could be done by rubbing the resin with an ordinary fur hat. This procedure was carried out at a time. Then the moving part of the electrophore fell as low as possible, but, not allowing contact with the lower "pan". This is what happens in it.

We know that the upper disk is made of metal, and the metals have a crystalline structure. These crystals can be considered as a lattice of positive metal ions, the cells of which are filled with electrons. These electrons can be likened to gas molecules moving continuously. As the upper disk approaches the lower one, the negative field of the resin on negatively charged electrons increases more and more. This leads to the fact that the electrons pushing out diffuse into the upper part of the disk and also into the soldered copper ball C. As a result, the upper part of the moving “frying pan” receives an excess of electrons with a deficiency in the lower one. Accordingly, the upper part of the movable disk and the ball C are negatively charged, and the lower is positive.

If the conductor ball B or C is now grounded, then the excess of electrons will flow from the top of the “pan” to the ground, making it neutral, but the lack of electrons in the bottom will remain. In his electrophore, Volta performed this procedure with the touch of a finger, and in the giant one, where the charge was large, the currents flowing through the experimenter were large and could injure the electricizer. Therefore, the designers of the machine came up with a special ground electrode, which worked automatically. When lowering the top of the pan, the ball C was in contact in the lowest position with the grounded ball D, through which electrons flowed into the ground. With a slight rise in the upper disk, the contact was interrupted and the lack of electrons already spread to the entire disk. And the potential of this charge increased with increasing height of the disk. This regularity was first noticed in world history back in 1759 by St. Petersburg academician F.U.T. Epinus.

Usually it is not entirely understood by students, although it is not forbidden for any person to repeat the experience of Epinus and this is relatively easy to do. This regularity is easily recorded by symbols in the formula, which is in any textbook of electrical engineering. The distrust of students in the results of this experiment is most likely caused by the idea of ​​a capacitor of variable capacity as a kind of perpetual motion machine from which it increases the charge potential. But the increase in potential comes at the expense of energy costs for the mechanical work of spreading the plates. After all, the capacitor plates charged with opposite charges are attracted to each other with a certain force that must be overcome.

Of course, it is impossible to simulate the process of a lightning discharge even with the help of such an electrophore giant, but until now, high potentials of charges of physics are obtained using van de graaff carswhere the charges are delivered to giant conductor balls mechanically.

We don’t know the potential of the charge received at the tsar electrophore, but an unknown author wrote in archival sources: “She (the machine) is ready to hit everyone who dares to touch her ball. It is known from experience that this electrophore can even kill a bull. Awful power! ”

The creators of the St. Petersburg giant.

The names of the designers of the giant machine are known to us from the words of the famous physicist Johann Bernoulli, who visited Petersburg in 1778. This is professor of the St. Petersburg Academy of Sciences Wolfgang Ludwig Kraft (1743-1814) and the mechanic of the same Academy, Russian craftsman I.P. Kulibin (1735-1818). In one of the modern books on electricity, one can read: “In the technical designs of induction machines, it is not easy for even a sophisticated eye to discern their simple fundamental principles.” The amazing person was Kulibin. He independently learned once to make telescopes no worse than English, and he personally polished the lenses. This was also the case with the electrophore, the essence of which is incomprehensible even now to many engineers. So the honor of constructing a giant electrophore belongs entirely to our compatriots.

The ethnic German V.L.Kraft cannot be considered a foreigner.He was born and died in St. Petersburg and in the history of physics his name is found in the Russian version - Login Yuryevich. It was not his fault that he was not allowed to work in the field of physics. Catherine II identified him as a teacher of her many grandchildren, among whom were future emperors Alexander I and Nicholas I.

Catherine II also broke her scientific career, too, to the St. Petersburg academician, pioneer of electric induction F.U.T. Epinus (1724-1802), one of the most promising specialists in the field of electricity of that time. He was obliged to decrypt the intercepted diplomatic correspondence of foreigners of St. Petersburg for the empress. But there is no doubt that he took part in the creation of a giant machine as a consultant. The overloads in deciphering diplomatic dispatches were so great that he became seriously ill with a mental illness and at the end of his life could not do science.

The fate of this car is unknown. By someone’s order, she was taken out of the Kunstkamera. And it may be not without reason. They were afraid of her, and for this reason. It was found that electrophores can work without giving him a preliminary charge. For the giant electrophore, there was enough light breeze above the lower pan. then to get high, deadly potentials on the top.

Why is this article written?

All of the above should show the reader that it is very easy to obtain electrical potentials even at home. To find the possibilities of their practical application is a matter of the brains of modern Kulibins. The possibilities of using static electricity probably exist even in everyday life. It is only necessary to become interested in inventors. And here are two examples of this.

In the 40s of the last century, the patriarch of Soviet physicists A.F. Ioffe developed an electrostatic generator to power an X-ray machine. The generator was simple and reliable. Then he came up with the idea to transfer all the country's electric power industry to electrostatics. Then step-up transformers and rectifiers for transmission lines become unnecessary. Direct current transmissions are the most economical, the more the loss during transformation disappears. But alas, for a large electric power industry such a system is impossible for the practical manufacture of generators. But there are also low-power consumers, especially since static generators do not create magnetic fields and are very light in weight.

It is known that back in 1748. the great American B. Franklin used a static-powered engine for practical purposes - he turned a turkey skewer over a roasting pan. Now such engines are forgotten, although they do not have windings, electrical steel and copper. This means that they can be very reliable in operation. Such engines are very promising for space applications. Moreover, the development of polymer chemistry promises us new dielectric materials.

So you can think in this direction.