Heinrich Rudolf Hertz was born into a lawyer's family in 1857 in Hamburg. From childhood, Hertz fell in love with science and was fond of writing poetry, as well as working on lathe.
Hertz was educated at a gymnasium and in 1876 entered the Munich University technical school, but in his second year he realizes that he made a mistake in choosing a profession. He decides to go into science and enters the University of Berlin, where he is noticed famous physicists Helmholtz and Kirchhoff. In 1880, Hertz graduated from the University of Berlin with doctorate. And in 1885 Hertz became a professor experimental physics V Polytechnic Institute in Karlsruhe, where he conducted world-famous experiments.
Some facts.
In the early 30s, in Russia, and then throughout the world, the unit of frequency of a periodic process, the hertz, was adopted. Subsequently, this value was entered into the table international system SI units. 1
A Hertz is equal to one complete oscillation in one second.
Physicist J. Thomson spoke of Hertz's work as a triumph of experimental skill, which was accompanied by ingenuity and caution in demonstrating the findings.
At one time, when Hertz’s mother told the master who taught the boy turning that her son had become a professor, he said with annoyance: “Oh, what a pity, he would have made a high-class turner!”
Famous experiments of Hertz.
Maxwell's theoretical statements suggest that electromagnetic waves can have reflective properties, be deformed and refracted. But any theory needs practice to be confirmed. But in those days, Maxwell and other physicists could not obtain electromagnetic waves in practice. This became possible in 1888, when Hertz was able to conduct experiments with electromagnetic waves and publish the results of his work.
Open oscillatory circuit or how to create a Hertz vibrator?
In a series of experiments, Hertz managed to create a practical source electromagnetic waves, which he called a vibrator. He created a device that consisted of two conducting spheres (sometimes cylinders were used) with a diameter of 10...30 cm, which were attached to rods cut in the middle. The ends of the cut rods ended in the form of a small sphere. There was a spark gap between the ends - a distance of several millimeters.
The spheres were connected to the secondary winding of the coil, which Ruhmkorff invented and which is the source high voltage.
What was the idea behind the Hertz vibrator?
Let's return to Maxwell's theory again:
Electromagnetic waves can only be studied through the passage of accelerated charges.
The energy of electromagnetic waves is proportional to the fourth power of its oscillation frequency.
It is known that accelerated charges can only be created in an oscillatory circuit, which made it possible to use it in the study of electromagnetic waves. One thing was required - to raise the frequency of charge oscillations. Based on Thomson's formula, which relates to the calculation of the cyclic frequency of oscillations:
it can be seen that in order to increase the frequency it is necessary to reduce the capacitive and inductive parameters of the circuit.
To reduce capacitance C, it is necessary to move the plates apart (increase the distance between them, and also reduce the area of the plate. The smallest capacitance is a simple wire.
In order to reduce the inductance L, it is necessary to reduce the number of turns in the coil. As a result of such manipulations, an ordinary wire comes out, which is called an open oscillatory circuit OCC.
To create an oscillatory action in the OCC, Hertz came up with the following scheme:
If we talk about the essence of what is happening in the Hertz vibrator, then we can say the following. The Ruhmkorff inductor makes it possible to create a high voltage (several kilovolts) at the ends of the secondary winding and a voltage that charges the spheres with opposite charges. After some time, an electric spark jumps into the spark gap, which makes the resistance of the air gap relatively small, which makes it possible to obtain high-frequency frequencies in the vibrator. damped oscillations, which last the entire period of the spark’s existence. Since the vibrator is an open oscillatory circuit, radiation of electromagnetic waves is generated.
But how can one determine the presence of electromagnetic waves, since they are not visible and cannot be touched?
For the detector, Hertz used a ring with a gap similar to the spark gap of a vibrator, which can be adjusted. The first ring in Hertz's experiments had a diameter of 1 meter, but then gradually decreased to a diameter of 7 cm.
Hertz called this discovery a resonator. In the course of his experiments, Hertz established that by changing the geometric characteristics of the resonator - the size, location and distance between the resonator and the vibrator, a certain result can be achieved: “harmony”, “syntony” (resonance). The presence of resonance will be observed when sparks appear in the spark gap. Hertz observed in his experiments sparks measuring 3-7 mm, and the sparking in the resonator was described by sparks measuring tenths of a millimeter. Such sparking was clearly visible only in a dark room, and sometimes it was necessary to use a magnifying glass.
What are the merits of Hertz?
During long and labor-intensive experiments in which simple and available means were used. Hertz managed to achieve incredible results in physics. He measured the wavelengths and calculated their propagation speeds. It has been proven that there is:
Reflection;
Refraction;
Diffraction;
Interference and polarization of waves;
The speed of electromagnetic waves was measured.
Hertz became a popular world scientist after reporting the results of his research in Berlin University(1888) and publication of the results of their experiments. Electromagnetic waves are also called “Hertzian rays”.
Hertz created charge oscillations in an electric vibrator circuit and observed how sparks jumped in a nearby resonator circuit and electromagnetic oscillations arose.
Hertz's amazing experiments were then successfully repeated in many countries and laboratories around the world. As we know, it began with reflection on Hertz’s experiments. wonderful research Alexander Stepanovich Popov, which then led to the invention of radio communications.
Hertz named the vibrations he recorded rays of electric force.
Portrait of Heinrich Hertz
He discovered that electric rays interfered and were refracted in a prism made of asphalt, just as light rays were refracted in a glass or quartz prism or lens. These rays differ only in their oscillation frequency or wavelength: for Hertz's rays, the wavelength ranged from 60 centimeters to several meters, while the wavelength of light rays ranged from 0.4 to 0.75 microns.
Heinrich Hertz wrote: “...it seems very probable that the experiments described prove the identity of light, heat rays and electromagnetic wave motion.”
Hertz's experiments forced scientists to increasingly recall Maxwell's bold theory, which united all light and electrical phenomena into a single whole.
Calculations have shown that the speed of Hertz's electromagnetic waves is equal to the speed of light!
More and more scientific facts in favor of Maxwell's theory accumulated.
The relationship derived by Maxwell was confirmed, according to which the refractive index of any substance equal to the root square of the product of its dielectric and magnetic permeability. Thus, a clear and obvious connection was established between the electrical and optical properties of the substance...
A photograph of the small setup that allowed him to discover that one oscillating circuit in a radio circuit could pick up electromagnetic waves sent by another circuit.
They found their simple explanation for the discovery of Bartholin and Malus: in a light beam containing transverse electromagnetic waves of the most diverse orientations, when reflected from dielectrics or passing through anisotropic crystals What remains are waves whose oscillations lie in a strictly defined plane - polarized waves.
In 1879, the English physicist John Kerr discovered that it is possible to observe the phenomenon in any homogeneous substance, such as a liquid or gas. birefringence under the influence of strong electrical and magnetic field.
Another confirmation close connection optical and electrical properties substances and at the same time evidence that a gas or liquid under certain conditions becomes similar to anisotropic crystals!
How close is it to scientific miracles XX century on the transformation of some substances into others...
In 1888, Hertz experimentally discovered electromagnetic waves and studied their properties.
Essentially Hertz needed to solve two experimental problems.
1. How to get an electromagnetic wave?
2. How to detect electromagnetic wave?
To obtain electromagnetic waves, it is necessary to create a changing electric or magnetic field in some region of space. Varying fields exist in an oscillatory circuit. The problem is that these fields are localized in a very small, limited area space: electric field between the capacitor plates, magnetic field inside the coil.
You can increase the area occupied by the fields by moving the capacitor plates apart and reducing the number of turns of the coil.
In the limit, the circuit consisting of a capacitor and a coil is converted into a piece of wire, which is called an open oscillatory circuit or Hertzian vibrator. Magnetic lines cover vibrator, power lines electric fields begin and end at the vibrator itself.
As the distance between the capacitor plates increases, its electrical capacity C decreases. Reducing the number of turns of the coil leads to a decrease in its inductance L. Changing the parameters of the circuit in accordance with Thomson's formula leads to a decrease in the period and an increase in the frequency of oscillations in the circuit. The period of oscillations in the circuit decreases so much that it becomes comparable to the propagation time electromagnetic field along the wire. This means that the process of current flow in an open oscillatory circuit ceases to be quasi-stationary: the current strength in different parts of the vibrator will no longer be the same.
The processes occurring in an open oscillatory circuit are equivalent to the oscillations of a fixed string, in which, as is known, a standing wave is established. Similar standing waves are installed for charge and current in an open oscillatory circuit.
It is clear that the current at the ends of the vibrator is always equal to zero. The current changes along the circuit, its amplitude is maximum in the middle (where the coil used to be).
When the current in the circuit is maximum, the charge density along the vibrator is zero. The figure shows the distribution of current and charge along the vibrator. There is no electric field around the vibrator at this moment, the magnetic field is at its maximum.
After a quarter of the period, the current becomes zero, and the magnetic field around the vibrator also “disappears.” The maximum charge density is observed near the ends of the vibrator; the charge distribution is shown in the figure. The electric field near the vibrator is at its maximum at this moment.
The changing magnetic field around the vibrator generates a vortex electric field, and the changing magnetic field generates a magnetic field. The vibrator becomes a source of electromagnetic wave. The wave runs in a direction perpendicular to the vibrator; oscillations of the electric field strength vector in the wave occur parallel to the vibrator. The magnetic field induction vector oscillates in a plane perpendicular to the vibrator.
The vibrator that Hertz used in his experiments was a straight conductor cut in half. The halves of the vibrator were separated by a small air gap. Via choke coils, the vibrator halves were connected to a high voltage source. The choke coils ensured a slow charging process for the vibrator halves. As the charge accumulated, the electric field in the gap increased. As soon as the magnitude of this field reached the breakdown value, a spark jumped between the halves of the vibrator. While the spark closed the air gap, high-frequency oscillations occurred in the vibrator and it emitted an electromagnetic wave.
The wavelength emitted by a vibrator depends on its size. Let's take advantage of the fact that a standing current wave is established in the vibrator. The nodes of this standing wave are located at the ends of the vibrator (there is no current here), the antinode of the standing wave is in the middle - here the current is maximum. The distance between the nodes of a standing wave is equal to half the wavelength, therefore,
Where L– length of the vibrator.
To detect an electromagnetic wave, you can take advantage of the fact that an electric field acts on charges. Under the influence of the electrical component of the electromagnetic wave free charges in the conductor must come into directed motion, i.e. current should appear.
In his experiments, Hertz used a receiving vibrator of the same size as the transmitting one. This ensured the equality of the natural frequencies of vibration of the vibrators, necessary to obtain resonance in the receiving vibrator. For successful reception waves, the receiving vibrator should be positioned parallel to the vector of the electric field strength, so that under the influence of electric force the electrons in the conductor could come into directed motion. The high-frequency current in the receiving conductor was detected by the glow of a small gas-discharge tube connected between the halves of the receiving vibrator.
You can “catch” the wave with a receiving circuit, placing it in the same plane with a radiating vibrator. With this arrangement of the circuit, the magnetic induction vector will be perpendicular to the circuit, and the magnetic flux penetrating the circuit will be maximum. When changing magnetic flux will appear in the circuit induced current, the indicator of which is again a small gas-discharge tube.
Hertz not only discovered an electromagnetic wave, but also observed its properties: reflection, refraction, interference, diffraction.
Test "Electromagnetic waves"
1. What is an electromagnetic wave?
A. diffusion process electrical vibrations V elastic medium
B. the process of propagation of a changing electric field
B. the process of propagation of changing electric and magnetic fields in space
D. the process of propagation of electrical vibrations in a vacuum
2. What oscillates in an electromagnetic wave?
A. electrons
B. any charged particles
B. electric field
D. electric and magnetic fields
3. What type of waves is an electromagnetic wave?
A. to the transverse
B. to longitudinal
B. EMF can be both transverse and longitudinal - depending on the environment in which it propagates
D. Electromagnetic waves can be both transverse and longitudinal - depending on the method of its emission
4. How are the electric field strength and magnetic field induction vectors in the wave located relative to each other?
5. Where correctly shown relative position velocity vectors, electric field strength and magnetic field induction in the wave?
6. What can be said about the phases of oscillations of the electric field strength vectors and the magnetic field induction in the wave?
A. vector and oscillate in one phase
B. vector and oscillate in antiphase
B. vector oscillations lag in phase from vector oscillations by
G. vector oscillations lag in phase from vector oscillations by
7. Indicate the relationship between the instantaneous values of the electric field strength vectors and the magnetic field induction in the wave.
A. 
IN. 
8. Provide an expression for calculating the speed of an electromagnetic wave in a vacuum.
A. 
B.V.G.
9. The ratio of the speed of propagation of electromagnetic waves in a medium to the speed of electromagnetic waves in a vacuum...
A. > 1 B.< 1 В. = 1
G. in some environments > 1, in other environments< 1.
10. Among long, short and ultra-short range radio waves highest speed waves propagate in a vacuum...
A. long range
B. short range
V. ultrashort range
D. the propagation speeds of waves of all ranges are the same
11. An electromagnetic wave carries...
A. Substance
B. Energy
B. Impulse
D. Energy and momentum
12. In what case does the radiation of an electromagnetic wave occur?
A. the electron moves uniformly and rectilinearly
B. flows along the spiral of an incandescent lamp AC
V. flows along the spiral of a flashlight lamp D.C.
D. a charged sphere floats in oil
13. An oscillating charge emits an electromagnetic wave. How will the amplitude of oscillations of the electric field strength vector change if, at a constant frequency, the amplitude of charge oscillations increases by 2 times?
A. will increase 2 times
B. will increase 4 times
G. will decrease by 2 times
D. will not change
14. An oscillating charge emits an electromagnetic wave. How will the amplitude of oscillations of the electric field strength vector change if, at a constant amplitude, the frequency of charge oscillations increases by 2 times?
A. will not change
B. will increase 2 times
V. will increase 4 times
G. will increase 8 times
15. An oscillating charge emits an electromagnetic wave. How will the intensity of the emitted wave change if, at a constant amplitude, the frequency of charge oscillations doubles?
A. will not change
B. will increase 2 times
V. will increase 4 times
G. will increase 8 times
16. In what direction is the intensity of the electromagnetic wave emitted by the Hertz vibrator maximum?
A. the intensity of the wave is the same in all directions
B. along the axis of the vibrator
V. in directions along perpendicular bisectors to the vibrator
D. the answer depends on the geometric dimensions of the vibrator
17. The wavelength at which ships transmit the SOS distress signal is 600 m. At what frequency are such signals transmitted?
A. 1, 8∙10 11 Hz B. 2∙10 -6 Hz C. 5∙10 5 Hz D. 2∙10 5 Hz
18. If mirror surface, on which the electromagnetic wave falls, is replaced by an absolutely black one, then the pressure produced by the wave on the surface...
A. will increase 2 times
B. will decrease by 2 times
V. will decrease by 4 times
G. won't change
19. When operating a radar - a device used to determine the distance to an object - the phenomenon is used...
Did you like the page? Like for friends:Hertz experiments Theory of electrical and magnetic phenomena, created by the works of the best mathematicians of the first half of this century and until recently accepted by almost all scientists, basically assumed the existence of special weightless electric and magnetic fluids that have the property of acting at a distance. The principle of Newton's doctrine of universal gravity- “actio in distans” - remained leading in the teaching of electricity and magnetism. But already in the 30s genius Faraday, leaving without consideration the question of essence electricity and magnetism, regarding external actions they expressed completely different thoughts. The attraction and repulsion of electrified bodies, electrification through influence, the interaction of magnets and currents and, finally, the phenomena of Faraday induction do not represent manifestations directly at a distance of the properties inherent in electric and magnetic fluids, but are only consequences of special changes in the state of the medium in which these are located, apparently directly influencing each other electric charges, magnets or conductors with currents. Since all such actions are equally observed in emptiness, as well as in space filled with air or other matter, then in the changes produced by the processes of electrification and magnetization on the air, Faraday saw the reason for these phenomena. Thus, just as through the emergence of special vibrations of the ether and the transmission of these vibrations from particle to particle, a light source illuminates any object remote from it, and in in this case Only through special disturbances in the medium of the same ether and the transmission of these disturbances from layer to layer do all electrical, magnetic and electromagnetic actions spread in space. A similar idea was the guiding principle in all of Faraday's research; she is most importantly and brought him to all his famous discoveries. But it was not soon and not easy that Faraday’s teachings became stronger in science. For decades, during which the phenomena discovered by him managed to undergo the most thorough and detailed study, Faraday’s basic ideas were either ignored or directly considered unconvincing and unproven. Only in the second half of the sixties did Faraday’s talented follower, who died so early, Clerk Maxwell, appear, who interpreted and developed Faraday’s theory, giving it a strictly mathematical character. Maxwell proved the necessity of existence final speed, with which the transfer of actions occurs through the intermediate medium electric current or magnet. This speed, according to Maxwell, should be equal to the speed at which light propagates in the medium under consideration. The environment involved in the transmission of electrical and magnetic actions, cannot be other than the same ether, which is allowed in the theory of light and radiant heat. The process of propagation of electrical and magnetic actions in space must be qualitatively the same as the process of propagation of light rays. All laws relating to light rays are fully applicable to electric rays. According to Maxwell, the phenomenon of light itself is an electrical phenomenon. A ray of light is a series of electrical disturbances, very small electrical currents, successively excited in the ether of the medium. What the change in the environment consists of under the influence of the electrification of some body, the magnetization of iron, or the formation of a current in some coil is still not known. Maxwell's theory does not yet make it possible to clearly imagine the very nature of the deformations it assumes. What is certain is that any change deformation of the medium produced in it under the influence of the electrification of bodies is accompanied by the emergence of magnetic phenomena in this environment and, conversely, any change in an environment of deformations resulting in it under the influence of some magnetic process, is accompanied by excitation electrical action. If at any point in the medium, deformed by the electrification of any body, an electric force is observed according to known direction, i.e., in this direction the one placed in the this place very small electrified ball, then with any increase or decrease in the deformation of the medium, together with an increase or decrease in the electric force at a given point, a magnetic force will appear in it in a direction perpendicular to the electric force - placed here magnetic pole will receive a push in a direction perpendicular to the electrical force. This is the consequence that follows from Maxwell's theory of electricity. Despite the enormous interest in the Faraday-Maxwell doctrine, it was met with doubt by many. Too bold generalizations flowed from this theory! The experiments of G. (Heinrich Hertz), carried out in 1888, finally confirmed the correctness of Maxwell's theory. G. managed, so to speak, to implement mathematical formulas Maxwell, it was actually possible to prove the possibility of the existence of electric, or, correctly, electromagnetic rays. As has already been noted, according to Maxwell’s theory, the propagation of a light beam is essentially the propagation of electrical disturbances successively formed in the ether, quickly changing their direction. The direction in which such disturbances, such as deformations, are excited, according to Maxwell, is perpendicular to the light beam. From here it is obvious that the direct excitation in any body of electrical currents very quickly changing in direction, i.e. excitation in a conductor of electric currents of alternating direction and of very short duration should cause corresponding electrical disturbances in the ether surrounding this conductor, rapidly changing in their direction , that is, it should cause a phenomenon qualitatively quite similar to what a ray of light represents. But it has long been known that when an electrified body or a Leyden jar is discharged, a whole series of electrical currents are formed in the conductor through which the discharge occurs, alternately in one direction or the other. A discharging body does not immediately lose its electricity; on the contrary, during the discharge it is recharged several times with one or the other electricity according to the sign. Successive charges appearing on the body decrease only little by little in magnitude. Such categories are called oscillatory. The duration of existence in a conductor of two successive flows of electricity during such a discharge, i.e., the duration electrical vibrations, or otherwise, the time interval between two moments at which a discharging body receives the largest charges appearing on it in succession, can be calculated from the shape and size of the discharging body and the conductor through which such a discharge occurs. According to theory, this duration of electrical oscillations (T) expressed by the formula: T = 2π√(LC). Here WITH stands for electrical capacity discharging body and L - self-induction coefficient conductor through which the discharge occurs (see). Both quantities are expressed according to the same system of absolute units. When using an ordinary Leyden jar, discharged through a wire connecting its two plates, the duration of electrical oscillations, i.e. T, determined in 100 and even 10 thousandths of a second. In his first experiments, G. electrified two metal balls (30 cm in diameter) differently and allowed them to discharge through a short and rather thick copper rod, cut in the middle, where an electric spark was formed between the two balls, which were mounted facing each other the ends of the two halves of the rod. Fig. 1 shows a diagram of G.'s experiments (rod diameter 0.5 cm, ball diameter b And b" 3 cm, the gap between these balls is about 0.75 cm and the distance between the centers of the balls S V S" equals 1 m). Subsequently, instead of balls, G. used square metal sheets (40 cm on each side), which he placed in one plane. Charging of such balls or sheets was carried out using a functioning Ruhmkorff coil. The balls or sheets were charged many times per second from the coil and then discharged through the copper rod located between them to form electric spark in between two balls b And b". The duration of the electrical oscillations excited in the copper rod exceeded a little one 100-thousandth of a second. In his further experiments, using, instead of sheets with halves of a copper rod attached to them, short thick cylinders with spherical ends, between which a spark jumped, G. received electrical vibrations, the duration of which was only about a thousand-millionth of a second. Such a pair of balls, sheets or cylinders, such vibrator, as G. calls it, from the point of view of Maxwellian theory, it is a center that propagates electromagnetic rays in space, that is, it excites electromagnetic waves in the ether, just like any light source that excites light waves around itself. But such electromagnetic rays or electromagnetic waves are not able to have an effect on the human eye. Only in the case when the duration of each electric train. the oscillation would reach only one 392-billionth of a second, the observer's eye would be impressed by these oscillations and the observer would see an electromagnetic beam. But to achieve such rapidity of electrical oscillations it is necessary vibrator, appropriate in size physical particles. So, to detect electromagnetic rays, special means are needed, apt expression W. Thomson (now Lord Kelvin), a special "electric eye". Such an “electric eye” was arranged by G in the simplest way. Let us imagine that at some distance from the vibrator there is another conductor. Disturbances in the ether excited by the vibrator should affect the state of this conductor. This conductor will be subject to sequential series impulses seeking to excite in it something similar to what caused such disturbances in the ether, i.e., seeking to form electrical currents in it that change in direction according to the speed of electrical oscillations in the vibrator itself. But impulses, successively alternating, are only able to contribute to each other when they are completely rhythmic with what they actually cause. electrical movements in such a conductor. After all, only in unison is a string tuned able to become noticeably vibrated by the sound emitted by another string, and thus able to appear independent sound source. So, the conductor must, so to speak, electrically resonate with the vibrator. Just as a string of a given length and tension is capable of oscillations known in terms of speed when struck, so in each conductor from electrical impulse Electrical oscillations can only occur during very specific periods. Having bent copper wire of the appropriate size in the form of a circle or rectangle, leaving only a small gap between the ends of the wire with small balls stolen on them (Fig. 2), of which one, by means of a screw, could approach or move away from the other, G. received, as he did named resonator to his vibrator (in most of his experiments, when the above-mentioned balls or sheets served as the vibrator, G. used copper wire 0.2 cm in diameter, bent in the form of a circle with a diameter of 35 cm, as a resonator). For a vibrator made of short thick cylinders, the resonator was a similar circle of wire, 0.1 cm thick and 7.5 cm in diameter. For the same vibrator, in his later experiments, G. built a resonator of a slightly different shape. Two straight wires, 0.5 cm dia. and 50 cm in length, located one on top of the other with a distance between their ends of 5 cm; from both ends of these wires facing each other, two other parallel wires of 0.1 cm in diameter are drawn perpendicular to the direction of the wires. and 15 cm in length, which are attached to the spark meter balls. No matter how weak the individual impulses themselves are from disturbances occurring in the ether under the influence of a vibrator, they, nevertheless, promoting each other in action, are able to excite already noticeable electrical currents in the resonator, manifested in the formation of a spark between the balls of the resonator. These sparks are very small (they reached 0.001 cm), but are quite sufficient to be a criterion for the excitation of electrical oscillations in the resonator and, by their size, serve as an indicator of the degree of electrical disturbance of both the resonator and the ether surrounding it. By observing the sparks appearing in such a resonator, Hertz examined at different distances and in various directions space around the vibrator. Leaving aside these experiments of G. and the results that were obtained by him, let us move on to research that confirmed the existence ultimate speed of propagation of electrical actions. Attached to one of the walls of the room in which the experiments were carried out was large sizes screen made of zinc sheets. This screen was connected to the ground. At a distance of 13 meters from the screen, a vibrator made of plates was placed so that the planes of its plates were parallel to the plane of the screen and the middle between the vibrator balls was opposite the middle of the screen. If a vibrator, during its operation, periodically excites electrical disturbances in the surrounding ether and if these disturbances propagate in the medium not instantly, but with a certain speed, then, having reached the screen and reflected back from the latter, like sound and light disturbances, these disturbances, together with those which are sent to the screen by a vibrator, form in the ether, in the space between the screen and the vibrator, a state similar to that which occurs under similar conditions due to the interference of counterpropagating waves, i.e. in this space the disturbances will take on the character "standing waves"(see Waves). The state of the air in places corresponding to "nodes" And "antinodes" of such waves, obviously, should differ significantly. Placing his resonator with its plane parallel to the screen and so that its center was on a line drawn from the middle between the vibrator balls normal to the plane of the screen, G. observed at different distances of the resonator from the screen, the sparks in it are very different in length. Near the screen itself, almost no sparks appear in the resonator, also at distances equal to 4.1 and 8.5 m. On the contrary, sparkles are greatest when the resonator is placed at distances from the screen equal to 1.72 m, 6.3 m and 10.8 m. G. concluded from his experiments that on average 4.5 m separate from each other those positions of the resonator in which the phenomena observed in it, i.e., sparks, turn out to be closely identical. G. obtained exactly the same thing with a different position of the resonator plane, when this plane was perpendicular to the screen and passed through a normal line drawn to the screen from the middle between the vibrator balls and when axis of symmetry the resonator (i.e., its diameter passing through the middle between its balls) was parallel to this normal. Only with this position of the resonator plane maxima sparks in it were obtained where, in the previous position of the resonator, minima, and back. So 4.5 m corresponds to the length "standing electromagnetic waves" arising between the screen and the vibrator in a space filled with air (the opposite phenomena observed in the resonator in its two positions, i.e., maxima sparks in one position and minima in the other, are fully explained by the fact that in one position of the resonator electrical oscillations are excited in it electrical forces,
so-called electrical deformations in the ether; in another position they are caused as a consequence of the occurrence magnetic forces,
i.e. they get excited magnetic deformations). Along the length of the "standing wave" (l) and by time (T), corresponding to one complete electrical oscillation in the vibrator, based on the theory of the formation of periodic (wave-like) disturbances, it is easy to determine the speed (v), with which such disturbances are transmitted in the air. This speed v = (2l)/T. In G.'s experiments: l= 4.5 m, T= 0.000000028". From here v= 320,000 (approximately) km per second, i.e. very close to the speed of light propagating in the air. G. studied the propagation of electrical vibrations in conductors, that is, in wires. For this purpose, an insulated copper plate of the same type was placed parallel to one vibrator plate, from which came a long wire stretched horizontally (Fig. 3). In this wire, due to the reflection of electrical vibrations from its insulated end, “standing waves” were also formed, the distribution of “nodes” and “antinodes” of which along the wire G. found using a resonator. G. derived from these observations for the speed of propagation of electrical vibrations in a wire a value equal to 200,000 km per second. But this definition is not correct. According to Maxwell's theory, in this case the speed should be the same as for air, i.e. it should be equal to the speed of light in air. (300,000 km per second). Experiments carried out after G. by other observers confirmed the position of Maxwell's theory. Having a source of electromagnetic waves, a vibrator, and a means of detecting such waves, a resonator, G. proved that such waves, like light waves, are subject to reflections and refractions and that electrical disturbances in these waves are perpendicular to the direction of their propagation, i.e., he discovered polarization in electric rays. For this purpose, he placed a vibrator that produces very fast electrical oscillations (a vibrator made of two short cylinders) in the focal line of a parabolic cylindrical mirror made of zinc; in the focal line of another similar mirror he placed a resonator, as described above, made of two straight wires . By directing electromagnetic waves from the first mirror onto some flat metal screen, G., with the help of another mirror, was able to determine the laws of reflection of electric waves, and by forcing these waves to pass through large prism, prepared from asphalt, determined their refraction. The laws of reflection and refraction turned out to be the same as for light waves. Using these same mirrors, G. proved that electric rays polarized, when the axes of two mirrors placed opposite each other were parallel under the action of a vibrator, sparks were observed in the resonator. When one of the mirrors was rotated 90° around the direction of the rays, i.e., the axes of the mirrors made a right angle to each other, any trace of sparks in the resonator disappeared. In this way, G.'s experiments proved the correctness of Maxwell's position. The G. vibrator, like a light source, emits energy into the surrounding space, which, through electromagnetic rays, is transmitted to everything that is able to absorb it, transforming this energy into another form accessible to our senses. Electromagnetic rays the quality is quite similar to rays of heat or light. Their difference from the latter lies only in the lengths of the corresponding waves. The length of light waves is measured in ten thousandths of a millimeter, while the length of electromagnetic waves excited by vibrators is expressed in meters. The phenomena discovered by G. later served as the subject of research by many physicists. In general, G.'s conclusions are fully confirmed by these studies. Now we know, moreover, that the speed of propagation of electromagnetic waves, as follows from Maxwell’s theory, changes along with changes in the medium in which such waves propagate. This speed is inversely proportional √K, Where TO the so-called dielectric constant of a given medium. We know that when electromagnetic waves propagate along conductors, electrical vibrations are “damped”, that when electric rays are reflected, their “voltage” follows the laws given by Fresnel for light rays, etc.
It has long been noticed that if you wrap a steel needle with wire and discharge a Leyden jar through this wire, then North Pole it does not always happen at the end of the needle where it could be expected in the direction of the discharge current and according to the rule... Encyclopedic Dictionary F. Brockhaus and I.A. Ephron
Encyclopedic Dictionary F.A. Brockhaus and I.A. Ephron
E. is called that contained in the body that communicates to this body special properties, causes in it the ability to act mechanically on some other bodies, to attract or, under certain conditions, repel them, and also causes in this body itself... Encyclopedic Dictionary F.A. Brockhaus and I.A. Ephron
The name given by Michael Faraday to bodies that do not conduct, or, otherwise, poorly conduct electricity, such as air, glass, various resins, sulfur, etc. Similar bodies also called insulators. Before Faraday's research, carried out in the 30s... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Ephron
When discharging any electrified body, a capacitor, a Leyden jar or a battery consisting of several such jars, the electric current appearing in the conductor through which the discharge is produced has a very definite... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Ephron
- (Hertz) famous German. physicist; genus. in 1857, educated in Berlin and Munich, was an assistant to Helmholtz; in 1883 he became priv. Assoc. By theoretical physics in Kiel, in 1885 as a professor at the Higher technical school in Karlsruhe; since 1889... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Ephron
- (physical) extremely thin, slightly dense and therefore not perceptibly subject to attraction, hypothetical types of substance; Such substances as liquids were previously considered caloric (caloricum), electricity, magnetism, light substance, ether... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Ephron
Depending on the group of phenomena, for the understanding and systematization of which the existence of attractive and repulsive forces is assumed, these latter acquire different names, such as: gravitational, electric, magnetic and... Encyclopedic Dictionary F.A. Brockhaus and I.A. Ephron
Attraction and repulsion Depending on the group of phenomena, for the understanding and systematization of which the existence of attractive and repulsive forces is assumed, these latter acquire different names, such as: forces of gravity, ... ... Wikipedia
The theory of electrical and magnetic phenomena, created by the works of the best mathematicians of the first half of this century and until recently accepted by almost all scientists, basically assumed the existence of special weightless electric and magnetic fluids that have the property of acting at a distance. The principle of Newton's doctrine of universal gravitation - "actio in distans" - remained guiding in the doctrine of electricity and magnetism. But already in the 30s the brilliant Faraday, leaving without consideration the question of essence electricity and magnetism, expressed completely different thoughts regarding their external actions. The attraction and repulsion of electrified bodies, electrification through influence, the interaction of magnets and currents and, finally, the phenomena of Faraday induction do not represent manifestations directly at a distance of the properties inherent in electric and magnetic fluids, but are only consequences of special changes in the state of the medium in which there are these apparently directly influencing each other electric charges, magnets or conductors with currents. Since all such actions are equally observed in emptiness, as well as in space filled with air or other matter, then in the changes produced by the processes of electrification and magnetization on the air, Faraday saw the reason for these phenomena. Thus, just as through the emergence of special vibrations of the ether and the transmission of these vibrations from particle to particle, a light source illuminates any object distant from it, and in this case only through special disturbances in the medium of the same ether and the transmission of these disturbances from the layer all electrical, magnetic and electromagnetic effects propagate in space to the layer. A similar idea was the guiding principle in all of Faraday's research; It was she who most importantly led him to all his famous discoveries. But it was not soon and not easy that Faraday’s teachings became stronger in science. For decades, during which the phenomena discovered by him managed to undergo the most thorough and detailed study, Faraday’s basic ideas were either ignored or directly considered unconvincing and unproven. Only in the second half of the sixties did Faraday’s talented follower, who died so early, Clerk Maxwell, appear, who interpreted and developed Faraday’s theory, giving it a strictly mathematical character. Maxwell proved the necessity of the existence of a finite speed at which the transfer of the effects of electric current or magnet occurs through an intermediate medium. This speed, according to Maxwell, should be equal to the speed at which light propagates in the medium under consideration. The medium that takes part in the transmission of electrical and magnetic actions cannot be other than the same ether, which is allowed in the theory of light and radiant heat. The process of propagation of electrical and magnetic actions in space must be qualitatively the same as the process of propagation of light rays. All laws relating to light rays are fully applicable to electric rays. According to Maxwell, the phenomenon of light itself is an electrical phenomenon. A ray of light is a series of electrical disturbances, very small electrical currents, successively excited in the ether of the medium. What the change in the environment consists of under the influence of the electrification of some body, the magnetization of iron, or the formation of a current in some coil is still not known. Maxwell's theory does not yet make it possible to clearly imagine the very nature of the deformations it assumes. What is certain is that any change deformation of the medium produced in it under the influence of the electrification of bodies is accompanied by the emergence of magnetic phenomena in this environment and, conversely, any change in an environment of deformations resulting in it under the influence of some magnetic process, it is accompanied by the excitation of electrical actions. If at any point in the medium, deformed by the electrification of some body, an electric force is observed in a known direction, i.e., in this direction a very small electrified ball placed in a given place will begin to move, then with any increase or decrease in the deformation of the medium, together with an increase or decrease in the electric force at a given point, a magnetic force will appear in it in a direction perpendicular to the electric force - the magnetic pole placed here will receive a push in the direction perpendicular to the electric force. This is the consequence that follows from Maxwell's theory of electricity. Despite the enormous interest in the Faraday-Maxwell doctrine, it was met with doubt by many. Too bold generalizations flowed from this theory! The experiments of G. (Heinrich Hertz), carried out in 1888, finally confirmed the correctness of Maxwell's theory. G. managed, so to speak, to implement Maxwell’s mathematical formulas; he actually managed to prove the possibility of the existence of electric, or, correctly, electromagnetic rays. As has already been noted, according to Maxwell’s theory, the propagation of a light beam is essentially the propagation of electrical disturbances successively formed in the ether, quickly changing their direction. The direction in which such disturbances, such as deformations, are excited, according to Maxwell, is perpendicular to the light beam itself. From here it is obvious that the direct excitation in any body of electrical currents very quickly changing in direction, i.e. excitation in a conductor of electric currents of alternating direction and of very short duration should cause corresponding electrical disturbances in the ether surrounding this conductor, rapidly changing in their direction , that is, it should cause a phenomenon qualitatively quite similar to what a ray of light represents. But it has long been known that when an electrified body or a Leyden jar is discharged, a whole series of electrical currents are formed in the conductor through which the discharge occurs, alternately in one direction or the other. A discharging body does not immediately lose its electricity; on the contrary, during the discharge it is recharged several times with one or the other electricity according to the sign. Successive charges appearing on the body decrease only little by little in magnitude. Such categories are called oscillatory. The duration of existence in a conductor of two successive flows of electricity during such a discharge, i.e., the duration electrical vibrations, or otherwise, the time interval between two moments at which a discharging body receives the largest charges appearing on it in succession, can be calculated from the shape and size of the discharging body and the conductor through which such a discharge occurs. According to theory, this duration of electrical oscillations (T) expressed by the formula:
T = 2π√(LC).
Here WITH stands for electrical capacity discharging body and L - self-induction coefficient conductor through which the discharge occurs (see). Both quantities are expressed according to the same system of absolute units. When using an ordinary Leyden jar, discharged through a wire connecting its two plates, the duration of electrical oscillations, i.e. T, determined in 100 and even 10 thousandths of a second. In his first experiments, G. electrified two metal balls (30 cm in diameter) differently and allowed them to discharge through a short and rather thick copper rod, cut in the middle, where an electric spark was formed between the two balls, which were mounted facing each other the ends of the two halves of the rod. Fig. 1 shows a diagram of G.'s experiments (rod diameter 0.5 cm, ball diameter b And b" 3 cm, the gap between these balls is about 0.75 cm and the distance between the centers of the balls S V S" equals 1 m).
Subsequently, instead of balls, G. used square metal sheets (40 cm on each side), which he placed in one plane. Charging of such balls or sheets was carried out using a functioning Ruhmkorff coil. The balls or sheets were charged many times per second from the coil and then discharged through a copper rod located between them, creating an electric spark in the gap between the two balls b And b". The duration of the electrical oscillations excited in the copper rod exceeded a little one 100-thousandth of a second. In his further experiments, using, instead of sheets with halves of a copper rod attached to them, short thick cylinders with spherical ends, between which a spark jumped, G. received electrical vibrations, the duration of which was only about a thousand-millionth of a second. Such a pair of balls, sheets or cylinders, such vibrator, as G. calls it, from the point of view of Maxwellian theory, it is a center that propagates electromagnetic rays in space, that is, it excites electromagnetic waves in the ether, just like any light source that excites light waves around itself. But such electromagnetic rays or electromagnetic waves are not able to have an effect on the human eye. Only in the case when the duration of each electric train. the oscillation would reach only one 392-billionth of a second, the observer's eye would be impressed by these oscillations and the observer would see an electromagnetic beam. But to achieve such rapidity of electrical oscillations it is necessary vibrator, in size corresponding to physical particles. So, to detect electromagnetic rays, special means are needed; in the apt expression of V. Thomson (now Lord Kelvin), a special “electric eye” is needed. Such an “electric eye” was arranged by G in the simplest way. Let us imagine that at some distance from the vibrator there is another conductor. Disturbances in the ether excited by the vibrator should affect the state of this conductor. This conductor will be subject to a successive series of impulses, tending to excite in it something similar to what caused such disturbances in the ether, i.e., tending to form electric currents in it, changing in direction according to the speed of electrical oscillations in the vibrator itself. But impulses, successively alternating, are only able to contribute to each other when they are completely rhythmic with the electrical movements they actually cause in such a conductor. After all, only a tuned string in unison is able to vibrate noticeably from the sound emitted by another string, and, thus, is able to appear as an independent sound source. So, the conductor must, so to speak, electrically resonate with the vibrator. Just as a string of a given length and tension is capable of oscillations of a certain speed when struck, so in each conductor an electric impulse can produce only electrical oscillations of quite certain periods. Having bent copper wire of the appropriate size in the form of a circle or rectangle, leaving only a small gap between the ends of the wire with small balls stolen on them (Fig. 2), of which one, by means of a screw, could approach or move away from the other, G. received, as he did named resonator to his vibrator (in most of his experiments, when the above-mentioned balls or sheets served as the vibrator, G. used copper wire 0.2 cm in diameter, bent in the form of a circle with a diameter of 35 cm, as a resonator).
For a vibrator made of short thick cylinders, the resonator was a similar circle of wire, 0.1 cm thick and 7.5 cm in diameter. For the same vibrator, in his later experiments, G. built a resonator of a slightly different shape. Two straight wires, 0.5 cm dia. and 50 cm in length, located one on top of the other with a distance between their ends of 5 cm; from both ends of these wires facing each other, two other parallel wires of 0.1 cm in diameter are drawn perpendicular to the direction of the wires. and 15 cm in length, which are attached to the spark meter balls. No matter how weak the individual impulses themselves are from disturbances occurring in the ether under the influence of a vibrator, they, nevertheless, promoting each other in action, are able to excite already noticeable electrical currents in the resonator, manifested in the formation of a spark between the balls of the resonator. These sparks are very small (they reached 0.001 cm), but are quite sufficient to be a criterion for the excitation of electrical oscillations in the resonator and, by their size, serve as an indicator of the degree of electrical disturbance of both the resonator and the ether surrounding it.
By observing the sparks appearing in such a resonator, Hertz examined the space around the vibrator at different distances and in different directions. Leaving aside these experiments of G. and the results that were obtained by him, let us move on to research that confirmed the existence ultimate speed of propagation of electrical actions. A large screen made of zinc sheets was attached to one of the walls of the room in which the experiments were carried out. This screen was connected to the ground. At a distance of 13 meters from the screen, a vibrator made of plates was placed so that the planes of its plates were parallel to the plane of the screen and the middle between the vibrator balls was opposite the middle of the screen. If a vibrator, during its operation, periodically excites electrical disturbances in the surrounding ether and if these disturbances propagate in the medium not instantly, but with a certain speed, then, having reached the screen and reflected back from the latter, like sound and light disturbances, these disturbances, together with those which are sent to the screen by a vibrator, form in the ether, in the space between the screen and the vibrator, a state similar to that which occurs under similar conditions due to the interference of counterpropagating waves, i.e. in this space the disturbances will take on the character "standing waves"(see Waves). The state of the air in places corresponding to "nodes" And "antinodes" of such waves, obviously, should differ significantly. Placing his resonator with its plane parallel to the screen and so that its center was on a line drawn from the middle between the vibrator balls normal to the plane of the screen, G. observed at different distances of the resonator from the screen, the sparks in it are very different in length. Near the screen itself, almost no sparks appear in the resonator, also at distances equal to 4.1 and 8.5 m. On the contrary, sparkles are greatest when the resonator is placed at distances from the screen equal to 1.72 m, 6.3 m and 10.8 m. G. concluded from his experiments that on average 4.5 m separate from each other those positions of the resonator in which the phenomena observed in it, i.e., sparks, turn out to be closely identical. G. obtained exactly the same thing with a different position of the resonator plane, when this plane was perpendicular to the screen and passed through a normal line drawn to the screen from the middle between the vibrator balls and when axis of symmetry the resonator (i.e., its diameter passing through the middle between its balls) was parallel to this normal. Only with this position of the resonator plane maxima sparks in it were obtained where, in the previous position of the resonator, minima, and back. So 4.5 m corresponds to the length "standing electromagnetic waves" arising between the screen and the vibrator in a space filled with air (the opposite phenomena observed in the resonator in its two positions, i.e., maxima sparks in one position and minima in the other, are fully explained by the fact that in one position of the resonator electrical oscillations are excited in it electrical forces, so-called electrical deformations in the ether; in another position they are caused as a consequence of the occurrence magnetic forces, i.e. they get excited magnetic deformations).
Along the length of the "standing wave" (l) and by time (T), corresponding to one complete electrical oscillation in the vibrator, based on the theory of the formation of periodic (wave-like) disturbances, it is easy to determine the speed (v), with which such disturbances are transmitted in the air. This speed
v = (2l)/T.
In G.'s experiments: l= 4.5 m, T= 0.000000028". From here v= 320,000 (approximately) km per second, i.e. very close to the speed of light propagating in the air. G. studied the propagation of electrical vibrations in conductors, that is, in wires. For this purpose, an insulated copper plate of the same type was placed parallel to one vibrator plate, from which came a long wire stretched horizontally (Fig. 3).
In this wire, due to the reflection of electrical vibrations from its insulated end, “standing waves” were also formed, the distribution of “nodes” and “antinodes” of which along the wire G. found using a resonator. G. derived from these observations for the speed of propagation of electrical vibrations in a wire a value equal to 200,000 km per second. But this definition is not correct. According to Maxwell's theory, in this case the speed should be the same as for air, i.e. it should be equal to the speed of light in air. (300,000 km per second). Experiments carried out after G. by other observers confirmed the position of Maxwell's theory.
Having a source of electromagnetic waves, a vibrator, and a means of detecting such waves, a resonator, G. proved that such waves, like light waves, are subject to reflections and refractions and that electrical disturbances in these waves are perpendicular to the direction of their propagation, i.e., he discovered polarization in electric rays. For this purpose, he placed a vibrator that produces very fast electrical oscillations (a vibrator made of two short cylinders) in the focal line of a parabolic cylindrical mirror made of zinc; in the focal line of another similar mirror he placed a resonator, as described above, made of two straight wires . By directing electromagnetic waves from the first mirror to some flat metal screen, G., with the help of another mirror, was able to determine the laws of reflection of electric waves, and by forcing these waves to pass through a large prism made of asphalt, he also determined their refraction. The laws of reflection and refraction turned out to be the same as for light waves. Using these same mirrors, G. proved that electric rays polarized, when the axes of two mirrors placed opposite each other were parallel under the action of a vibrator, sparks were observed in the resonator. When one of the mirrors was rotated 90° around the direction of the rays, i.e., the axes of the mirrors made a right angle to each other, any trace of sparks in the resonator disappeared.
In this way, G.'s experiments proved the correctness of Maxwell's position. The G. vibrator, like a light source, emits energy into the surrounding space, which, through electromagnetic rays, is transmitted to everything that is able to absorb it, transforming this energy into another form accessible to our senses. Electromagnetic rays are quite similar in quality to rays of heat or light. Their difference from the latter lies only in the lengths of the corresponding waves. The length of light waves is measured in ten thousandths of a millimeter, while the length of electromagnetic waves excited by vibrators is expressed in meters. The phenomena discovered by G. later served as the subject of research by many physicists. In general, G.'s conclusions are fully confirmed by these studies. Now we know, moreover, that the speed of propagation of electromagnetic waves, as follows from Maxwell’s theory, changes along with changes in the medium in which such waves propagate. This speed is inversely proportional √K, Where TO the so-called dielectric constant of a given medium. We know that when electromagnetic waves propagate along conductors, electrical vibrations are “damped”, that when electric rays are reflected, their “voltage” follows the laws given by Fresnel for light rays, etc.
G.'s articles concerning the phenomenon under consideration, collected together, are now published under the title: H. Hertz, “Untersuchungen über die Ausbreitung der elektrischen Kraft” (Lpts., 1892).
AND. Borgman.
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