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MOST IMPORTANT SCIENTIFIC DISCOVERIES
Oersted's law. History and essence of scientific discovery
Directory / The most important scientific discoveries The idea of the connection between electricity and magnetism, which goes back to the simplest similarity between the attraction of fluffs by amber and iron filings by a magnet, was in the air, and many of the best minds of Europe were carried away by it. In the literature, the facts of magnetization of steel needles by an electric spark, demagnetization of compasses by lightning were known. Aldini's treatise on galvanism (1804) mentions Mojon, who magnetized a steel needle with a voltaic column, and Romagnosi, who observed the deflection of a magnetic needle under the action of a voltaic column. But all these facts were in the nature of random observations and not only were not generalized, but were not even described with any precision. Oersted's merit lies, first of all, in the fact that he understood the importance and novelty of his discovery and drew the attention of the scientific world to it. "Scientific Danish physicist, professor," wrote Ampere, - with his great discovery paved a new path of research for physicists. These studies have not remained fruitless; they attracted to the discovery of many facts worthy of the attention of all who are interested in progress. Hans Christian Oersted (1777-1851) was born on the Danish island of Langeland in the town of Rydkobing in the family of a poor pharmacist. The family was constantly in need, so the brothers Hans Christian and Anders had to get their primary education wherever they could. Already at the age of twelve, Hans was forced to stand at the counter of his father's pharmacy. Here medicine captivated him for a long time, displacing chemistry, history, literature, and further strengthened his confidence in his scientific mission. He decides to enter the University of Copenhagen, where he takes on everything - medicine, physics, astronomy, philosophy, poetry. The gold medal of the university in 1797 was awarded to him for his essay "The Limits of Poetry and Prose". His next work, also highly regarded, dealt with the properties of alkalis, and the dissertation for which he received the title of Doctor of Philosophy was devoted to medicine. At twenty, Oersted received a degree in pharmacy, and at twenty-two, a Ph.D. Having brilliantly defended his dissertation, Hans goes to the university for an internship in France, Germany, Holland. There, Oersted listened to lectures on the possibilities of studying physical phenomena with the help of poetry, on the connection between physics and mythology. In 1806, Oersted became a professor at the University of Copenhagen. Fascinated by the philosophy of Schelling, he thought a lot about the relationship between heat, light, electricity and magnetism. In 1813, his work "Investigations into the Identity of Chemical and Electrical Forces" was published in France. In it, he first expresses the idea of a connection between electricity and magnetism. He writes: "You should try to see if electricity ... produces any action on the magnet ..." His considerations were simple: electricity gives rise to light - a spark, sound - crackling, finally, it can produce heat - a wire that closes the clamps power source, heats up. Can't electricity produce magnetic actions? They say that Oersted did not part with the magnet. That piece of iron must have continually made him think in that direction. The magnet must have traveled quite a few miles in Oersted's coat. Today, any schoolchild can easily reproduce Oersted's experiment, demonstrate a "vortex of electrical conflict" by pouring iron filings on cardboard, through the center of which a current-carrying wire passes. But it was not easy to detect the magnetic effects of the current. The Russian physicist Petrov tried to detect them by connecting the poles of his battery with iron and steel plates. He did not find any magnetization of the plates after a few hours of running current through them. There is information about other observations, but it is known with full certainty that the magnetic effects of the current were observed and described by Oersted. On February 15, 1820, Oersted, already emeritus professor of chemistry at the University of Copenhagen, gave a lecture to his students. The lecture was accompanied by demonstrations. On the laboratory table were a current source, a wire that closed its clamps, and a compass. At the time when Oersted closed the circuit, the compass needle flinched and turned. When the circuit was opened, the arrow returned back. This was the first experimental confirmation of the connection between electricity and magnetism, something that many scientists have been looking for for so long. It would seem that everything is clear. Oersted showed the students another confirmation of the long-standing idea of the universal connection of phenomena. But why are there doubts? Why did so much controversy subsequently flare up around the circumstances of this event? The fact is that the students who attended the lecture later told something completely different. According to them, Oersted wanted to demonstrate at the lecture only an interesting property of electricity to heat the wire, and the compass ended up on the table quite by accident. And it was by chance that they explained that the compass lay next to this wire, and quite by chance, in their opinion, one of the sharp-sighted students drew attention to the turning arrow, and the surprise and delight of the professor, according to them, were genuine. Oersted himself, in his later works, wrote: “All those present in the audience were witnesses to the fact that I had announced the result of the experiment in advance. The discovery, therefore, was not an accident, as Professor Hilbert would like to conclude from those expressions that I used when I first announced about opening." Is it a coincidence that it was Oersted who made the discovery? After all, a happy combination of the necessary instruments, their mutual arrangement and "modes of operation" could be obtained in any laboratory? Yes it is. But in this case, randomness is natural - Oersted was among the then few researchers studying the connections between phenomena. However, it is worth returning to the essence of Oersted's discovery. It must be said that the deviation of the compass needle in the lecture experiment was very small. In July 1820, Oersted repeated the experiment again, using more powerful batteries of current sources. Now the effect became much stronger, and the stronger, the thicker the wire with which he closed the battery contacts. In addition, he found out one strange thing that does not fit into Newton's ideas about action and reaction. The force acting between the magnet and the wire was not directed along the straight line connecting them, but perpendicular to it. In Oersted's words, "the magnetic effect of an electric current has a circular motion around it." The magnetic needle never pointed to the wire, but was always directed tangentially to the circles encircling this wire. It was as if invisible clots of magnetic forces swirled around the wire, drawing a light compass needle. This is what surprised the scientist. That is why in his four-page "pamphlet" he, fearing distrust and ridicule, carefully enumerates the witnesses, not forgetting to mention any of their scientific merits. Oersted, giving, in general, an incorrect theoretical interpretation of the experiment, planted a deep thought about the vortex nature of electromagnetic phenomena. He wrote: "In addition, from the observations made, it can be concluded that this conflict forms a vortex around the wire." In other words, magnetic field lines surround a current-carrying conductor, or electric current is a magnetic field vortex. This is the content of the first basic law of electrodynamics, and this is the essence of the discovery of the scientist. Oersted's experience proved not only the connection between electricity and magnetism. What was revealed to him was a new mystery that did not fit into the framework of known laws. On July 21, 1820, in Copenhagen, the pamphlet "Experiments Concerning the Action of Electric Conflict on a Magnetic Needle" was published in Latin. Oersted sent it to all scientific institutions and physics journals. By this he wanted to emphasize the importance of his discovery. And, indeed, Oersted's discovery made an impression of a scientific sensation and caused such a powerful resonance that one can say without exaggeration: there was a rebirth of galvanism. As a result of Oersted's discovery, it was possible to establish a connection between two groups of phenomena, which since the time of Hilbert were considered fundamentally different. A new type of interaction has been opened. So far, physics has known central forces. The wire does not attract or repel the poles of the arrow, but sets it perpendicular to its length. "Oersted's experiment is completely contrary to the elementary rules of mechanics," notes Arago. Finally, a new discovery gave physicists the means to build a sensitive and convenient indicator of electric current. And already in September 1820, Schweigger invented the multiplier, and in the 67th volume of the Gilbert Annals for 1821, Poggendorf's description of the design of the multiplier in his modern school uniform appeared. Finally, the efficiency and flexibility of the new interaction contained the seed of future technical applications of electrical power. After the release of Oersted's memoir, further events developed at a very unusual pace for the then leisurely science. A few days later, the memoir appeared in Geneva, where Arago was visiting at that time. The very first acquaintance with Oersted's experience proved to him that the answer had been found to the problem that he and many others had struggled with. The impression of the experiments was so great that one of those present at the demonstration stood up and excitedly uttered the phrase that later became famous: "Gentlemen, there is a revolution!" Arago returns to Paris shocked. At the very first meeting of the Academy, which he attended immediately upon his return, on September 4, 1820, he makes an oral report on Oersted's experiments. The notes made in the academic journal by the lazy hand of the recorder testify that the academicians asked Arago already at the next meeting, on September 22, to show all those present Oersted's experience, as they say, "in full size." Academician Ampère listened to Arago's message with special attention. He, perhaps, felt at that moment that the time had come for him, in the face of the whole world, to take the baton of discovery from the hands of Oersted. He had been waiting for this hour for a long time - about twenty years, like Arago and like Oersted. And then the hour struck - on September 4, 1820, Ampère realized that he had to act. In just two weeks, he announced the results of his research to the world. Author: Samin D.K.
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