Interaction of electric current and magnet. Development of the basics of electrodynamics

Expanding and deepening the research of electrical phenomena led to the discovery and study of new properties of electric current. In 1820, H.H. Oersted's experiments on observing the action of a current on a magnetic needle were published and demonstrated, which aroused great interest among scientists of different countries and received further deepening and development in their work.

A small (less than 5 pages) pamphlet Oersted "Experiments on the Action of Electric Conflict on a Magnetic Arrow" made a sensation among European physicists.

It is noteworthy that Oersted concluded that the "electric conflict" (ie, the oncoming movement of positive and negative "electrical matter") in the conductor "... is not limited to a conductive wire, but has an extensive sphere of activity around this wire ... This The conflict forms a vortex around the wire. "

Obviously, Oersted was mistaken, believing that a collision of dissimilar electricity is acting on the magnetic needle. But the connection between electrical and magnetic phenomena Oersted suggested in one of his works, published in 1812: "It should be tested, does not electricity produce in its most hidden stage any action on the magnet as such."

Shortly after the publication of this pamphlet (in 1820), the German physicist Johann H. S. Schweiger (1779-1857) proposed using the deflection of a magnetic needle by an electric current to create the first measuring device, a current indicator.

His device, called the "multiplier" (ie, multiplying) was a magnetic needle placed inside a frame consisting of turns of wire. However, due to the influence of terrestrial magnetism on the magnetic arrow of the multiplier, its readings were inaccurate.

Ampere in 1821 showed the possibility of eliminating the influence of terrestrial magnetism with the help of an astatic pair, representing the bottom of the magnetic arrows fixed on a common copper axis and parallel to each other, with poles facing in opposite directions.

In 1825 the Florentine professor Leopoldo Pobili (1784-1835) combined an astatic couple with a multiplier and arranged a more sensitive instrument in this way - a prototype of a galvanometer.

In 1820 DF Arago discovered a new phenomenon - the magnetization of the conductor by a current flowing through it. If the copper wire, connected with poles of the voltaic column, was immersed in iron sawdust, the latter evenly stuck to it. When the current was turned off, the sawdust fell behind. When Ara-go took iron instead of copper wire (from soft iron), it temporarily magnetized. A piece of steel with this magnetization became a permanent magnet.

On the recommendation of Ampere, Arago replaced the straight wire with a wire spiral, and the magnetization of the needle placed inside the helix was strengthened. So the solenoid was created. Arago's experiments proved for the first time the electrical nature of magnetism and the possibility of magnetizing steel with an electric current.

In the process of research, Arago discovered (in 1824) one more new phenomenon, which he called the "magnetism of rotation" and consisted in the fact that when a metal plate (copper) above the magnetic needle (or below it) rotates, the latter also comes to rotation. To explain this phenomenon, neither Arago nor Amper himself could. The correct explanation of this phenomenon was given Faraday only after the discovery of the phenomenon of electromagnetic induction.

A new step from qualitative observations of the effect of current on a magnet to the determination of quantitative dependences was the establishment of the law of the action of current on a magnet by French scientists Jean Baptiste Biot (1774-1862) and Felix Sawar (1791-1841).

After a series of experiments, they established (in 1820) the following: "if an unlimited length of wire with a volt current passing along it acts on a particle of northern or southern magnetism located at a known distance from the middle of the wire, the resultant of all forces exiting the wire is directed Perpendicular to the shortest distance of the particle from the wire, and the overall effect of the wire on any (southern or northern) magnetic element is inversely proportional to the distance of the latter to the wire. "

The detection of the tangential component of the force made it possible to explain the rotational nature of the motion of the conductor relative to the magnet. The French scientist Pierre Simon Laplace (1749-1827) subsequently showed that the force of action created by a small section of the conductor varies inversely with the square of the distance.

The most important scientific and methodological significance in extending the study of new phenomena was the work of one of the largest French scientists, André Marie Ampere (1775-1836), who laid the foundations of electrodynamics.

Amper was an unusually gifted man by nature. Despite the fact that he did not have a chance to study at school, he had no teachers, except his father - a highly educated businessman, with remarkable tenacity, independently mastering his knowledge, became one of the most educated people of his time.

Physics and mathematics, astronomy and chemistry, zoology and philosophy - in all these sciences the encyclopaedic knowledge of Ampere was clearly manifested. He was only 13 years old when he presented his first mathematical work to the Lyons Academy of Sciences, Literature and Art. By the time he was 14, he had studied all 20 volumes of the famous Encyclopaedia by Diderot and d'Alembert, and by 18 he had thoroughly studied the works of L. Euler, D. Boriulli and J. Lagrange, knew Latin and several foreign languages.

Ampere's personal life was full of tragic events: an 18-year-old boy, he was shocked by the execution on his father's guillotine as a supporter of the Girondins (1793), several years later he buried his beloved wife; Very sad was the fate of his daughter - it caused a serious heart disease that brought him to the grave.

But despite tremendous nervous tension, Amper managed to find the strength to tirelessly engage in fundamental scientific research and make an unfading contribution to the treasury of world civilization.

His research in the field of electromagnetics opened a new page in the history of electrical engineering. And when studying these phenomena, Ampere's amazing abilities were clearly manifested.

He first learned about the experiences of Oersted at the meeting of the Paris Academy of Sciences, where he repeated them during his report to Arago. Ampere, with admiration, intuitively sensed the importance of this discovery, although he had not previously studied electromagnetic phenomena.

And exactly in a week (only a week!) September 18, 1820 Amper speaks at a meeting of the Academy with a report on the interaction of currents and magnets, and then almost in a row - week after week (the sessions of the Academy of Sciences were held weekly) he expounds to the leading French scientists the results His experimental and theoretical generalizations, which were later reflected in his famous work on electrodynamics.

In one of his letters, Amper emphasizes that he "created a new theory of a magnet that reduces all phenomena to galvanic phenomena." The logic of his generalizations is striking: if the current is a magnet, then two currents must interact like magnets. Now it seems obvious, but no one so clearly indicated it before Ampère. Brilliant knowledge of mathematics allowed Ampere to theoretically generalize his research and formulate a well-known law bearing his name.

Deserves attention to the philosophical work of Ampere "The experience of philosophy of science, or an analytical presentation of the natural classification of all human knowledge" (1834). In our time many works devoted to the science of science "science of sciences" have been published. With his "Classification" Ampere laid down the foundations of this important field of scientific knowledge more than a hundred years ago.

Let us consider in more detail the work of Ampere in the field of electromagnetism.

First of all, we note that Ampere first introduced the term "electric current" and the concept of the direction of the electric current. By the way, he suggested that we consider the "flow of positive electricity" (from plus to minus in the external circuit) as the direction of the current.

Observing the deflection of the magnetic needle under the influence of current flowing through the conductor, Amper managed to formulate a rule that allows to determine the direction of the deviation of the arrow, depending on the direction of the current in the conductor.

This rule was widely known at that time as the "swimmer's rules" and was formulated as follows: "If one mentally places himself in such a way that the current passes from the observer's legs to the head and that his face is turned towards the magnetic needle, then under the influence The north pole of the magnetic needle will always deviate to the left. "

Of particular importance were Ampere's research on the interactions of circular and linear currents. He approached these researches, based on the following reasoning: if the magnet is similar in its properties to a coil or an annular conductor streamlined by a current, then two circular currents should act on each other like two magnets.

Having discovered the interaction of circular currents, Amper began to study linear currents. To this end, he built the so-called "Ampere machine", in which one conductor could change position relative to another conductor. During these experiments, it was found that two linear currents attract or repel each other, depending on whether the currents have the same direction or different.

A series of these experiments enabled Ampere to establish the law of interaction of linear currents: "Two parallel and identically directed currents are mutually beaten, while two parallel and oppositely directed currents are mutually repelled." Discovered phenomena Ampere proposed to call "electrodynamic" in contrast to electrostatic phenomena.

Summarizing the results of his experimental work, Amper derived a mathematical expression for the interaction force of currents, just as Coulomb did with respect to the interaction of static charges. Ampere solved this problem by an analytical method, proceeding from Newton's principles on the interaction of masses and likening these masses to two elements of a current arbitrarily located in space. At the same time, Ampere suggested that the interaction of current elements occurs along a straight line connecting the midpoints of these elements, and that it is proportional to the length of the current elements and to the currents themselves. The first memoir of Ampere on the interaction of electric currents was published in 1820.

The electrodynamic theory of Ampere is set forth by him in the work "Theory of electrodynamic phenomena, derived exclusively from experience," published in Paris in 1826-1827. Ampere derived a well-known mathematical expression of the law of interaction between two elements of the current.

Based on the works of his predecessors, as well as on the important results of his research, Ampere came to a fundamentally new conclusion about the cause of the phenomena of magnetism.

Denying the existence of special magnetic liquids, Amper claimed that the magnetic field is of electrical origin. All magnetic phenomena were reduced to "purely electric actions". Based on the identity of the action of circular currents and magnets, Amper came to the conclusion that the magnetism of any particle is due to the presence of circular currents in this particle, and the properties of the magnet as a whole are due to electric currents located in planes perpendicular to its axis.

Amper stressed that "... these currents around the axis of the magnet actually exist, or rather that magnetization is an operation through which particles began to communicate the property of exciting these currents for the same electromotive effect as is found in the voltaic column ... Magnetic phenomena Are caused solely by electricity ... there is no difference between the two poles of a magnet, like their position relative to the currents from which this magnet consists. "

The hypothesis of molecular circular currents developed by Ampere was a new progressive step on the way to a materialistic interpretation of the nature of magnetic phenomena.

Ampere in 1820, the idea was expressed about the possibility of creating an electromagnetic telegraph based on the interaction of a conductor with a current and a magnetic needle. However, Amper proposed to take "as many conductors and magnetic arrows as there are letters ..., placing each letter on a separate arrow." Obviously, such a design of the telegraph would be quite cumbersome and expensive, which, apparently, prevented the practical realization of Ampere's proposal. It took some time to find a more real way of creating a telegraph.

The significance of Ampere's work for science was very great. Through his research, Ampere proved the unity of electricity and magnetism and convincingly refuted the ideas that existed before him about a magnetic fluid. The laws of the mechanical interaction of electric currents established by him are among the largest discoveries in the field of electricity.

Ampere's outstanding contribution received the highest evaluation (in 1881). The First International Congress of Electricians gave the unit of current strength the name "Ampere". He was deservedly called "Newton of electricity". He was a member of the Paris Academy of Sciences (since 1814), and many other world academies, including the Petersburg Academy (since 1830).

Veselovsky O. N. Shneberg A. Ya "Essays on the history of electrical engineering"