Determination of elementary electrical charge by electrolysis. BUT

Ministry of Education of the Russian Federation

Amur State Pedagogical University

Methods for determining elementary electric charge

Performed student 151g.

Venseliev A.A.

Checked: Cerantev TG

Introduction

1. Prehistory of the opening of an electron

2. Electron opening history

3. Experiments and methods of opening an electron

3.1.Trom Thomson

3.2. Specific Rutherford

3.3. Metility milliken

3.3.1. short biography

3.3.2. Installation Description

3.3.3. Calculation elementary charge

3.3.4. Conclusions from the method

3.4. Common visualization method

Conclusion.

Introduction:

Electron - the first opening of the elementary particle in time; Material carrier of the least mass and the smallest electric charge in nature; Compound part of the atom.

Electron charge - 1,6021892. 10 -19 CL

4,803242. 10 -10 units. SGSE

Electron mass 9,109534. 10 -31 kg

Specific charge E / M E 1,7588047. 10 11 CL. kg -1.

Electron spin is 1/2 (in units H) and has two projections ± 1/2; Electrons subordinate to Fermi Dirac statistics, fermions. They have the principle of ban on Pauli.

The magnetic moment of the electron is - 1.00116 m b, where m b - magneton boron.

Electrical particle electron. According to experimental data, T E\u003e 2 lifetime. 10 22 years old.

Not involved in strong interaction, Lepton. Modern physics considers the electron as a truly elementary particle that does not possess the structure and sizes. If the latter and different from zero, then the radius of the electron R e< 10 -18 м

1. Customer opening

The opening of the electron was the result of numerous experiments. By the beginning of the XX century. The existence of an electron was established in a number of independent experiments. But, despite the colossal experimental material, accumulated by whole national schools, the electron remained a hypothetical particle, for the experience has not yet responded to a number of fundamental issues. In reality, the "discovery" of the electron was stretched more than the attachment and was not completed in 1897; Many scientists and inventors took part in it.

First of all, there was not a single experience in which individual electrons would participate. The elementary charge was calculated based on the measurements of the microscopic charge under the assumption of the justice of a series of hypotheses.

The uncertainty was in a fundamentally important point. At first, the electron appeared as the result of the atomistic interpretation of electrolysis laws, then it was discovered in the gas discharge. It was not clear whether physics actually deal with the same object. A large group of skeptical natural scientists believed that the elementary charge is the statistical average charges of the most diverse value. Moreover, none of the experiments to measure the charge of an electron did not give strictly repetitive values.
There were skeptics who generally ignored the opening of the electron. Academician A.F. Ioffe in memories of his teacher V.K. X-ray wrote: "Until 1906 - 1907. The word electronic should not be pronounced in the University of Munich Physics Institute. X-ray considered it an unproved hypothesis used often without sufficient grounds without need. "

The question of the mass of the electron was not resolved, it was not proved that both conductors, and on dielectric charges consist of electrons. The concept of "electron" did not have an unequivocal interpretation, because the experiment did not reveal the structures of the atom (the planetary model of Rutherford will appear in 1911, and Boro theory in 1913).

The electron did not enter theoretical constructions. The Lorentz electronic theory appeared continuously distributed charge density. In the theory of metallic conductivity, developed friend, it was about discrete charges, but these were arbitrary charges, which did not impose any restrictions.

The electron has not come out of the framework of the "clean" science. Recall that the first electronic lamp appeared only in 1907. To move from faith to conviction, it was necessary primarily to insulate an electron, invent the method of direct and accurate measurement of the elementary charge.

The solution to this task did not make himself wait. In 1752, the idea of \u200b\u200bdiscreteness of electric charge B. Franklin was first expressed for the first time. Experimentally discreteness of charges was substantiated by the laws of electrolysis, open M. Faraday in 1834. The number of elementary charge (the smallest electric charge found in nature) was theoretically calculated on the basis of electrolysis laws using the Avogadro number. Direct experimental measurement of elementary charge was performed by R. Millique in classical experiments made in 1908 - 1916. These experiments also gave an irrefutable proof of an electricity atomism. According to the basic views of the electronic theory, the charge of any body arises as a result of a change in the amount of electrons contained in it (or positive ions, the charge value of which is multiple electron charge). Therefore, the charge of any body should be changed from jump-like and such portions that contain a whole number of electron charges. Having installed on the experience of the discrete nature of the change of electrical charge, R. Millique was able to obtain confirmation of the existence of electrons and determine the charge value of one electron (elementary charge) using the oil droplet method. The method is based on the study of the movement of charged oil droplets in a homogeneous electric field Famous tension E.

2. Electron discretion:

If you distract from the fact that it was preceded by the opening of the first elementary particle - an electron, and from what happened to this outstanding event, it is possible to say briefly: in 1897, the famous English physicist Thomson Joseph John (1856-1940) measured the specific charge Q / M cathode-ray particles - "corpuscles", as he called them, to deviate cathode rays *) in electric and magnetic fields.

From the comparison of the obtained number with a specific charge of a monovalent hydrogen ion known at that time, by indirect reasoning, it came to the conclusion that the mass of these particles received later than the name "electrons" is significantly less (more than a thousand times) the mass of the lightest hydrogen ion.

In the same, 1897, he put forward a hypothesis that electrons are an integral part of atoms, and cathode rays are not atoms or non-electromagnetic radiation, as some researchers of the properties of the rays believed. Thomson wrote: "Thus, cathode rays are a new state of a substance substantially different from the usual gaseous state ...; In this new state, the matter is a substance from which all the elements are built."

Since 1897, the corpuscular model of cathode rays began to conquer general recognition, although the nature of electricity was a variety of judgments. Thus, the German physicist E.Vihert believed that "electricity is something imaginary, existing only in thoughts", and the famous English physicist Lord Kelvin in the same, 1897 wrote about electricity as a certain "continuous liquid".

Thomson's thought about cathode-ray corpuscles as the main components of the atom was not met with great enthusiasm. Some of his colleagues decided that he mystified them when it suggested that particles of cathode rays should be considered as possible components of an atom. The true role of Tomson corpuscles in the structure of an atom could be understood in combination with the results of other studies, in particular, with the results of analyzing the spectra and studying radioactivity.

On April 29, 1897, Thomson made his famous message at a meeting of the Royal Society of London. The exact time of the opening of the electron is a day and an hour - it is impossible to call in mind its originality. This event has become the result of Thomson's many years of work and its employees. Neither Thomson nor anyone ever observed an electron in a literal sense, no one managed to select a separate particle from the beam of cathode rays and measure its specific charge. The opening author is J.J.Tomson because his ideas about the electron were close to modern. In 1903, he proposed one of the first models of the atom - "pudding with raisin", and in 1904 suggested that the electrons in the atom are divided into groups, forming various configurations that determine the frequency of chemical elements.

The opening place is exactly known - Cavendish Laboratory (Cambridge, United Kingdom). Created in 1870, J.K. Maxwell, in the next one hundred years she became a "cradle" of a whole chain of brilliant discoveries in various fields of physics, especially in atomic and nuclear. Directors were: Maxwell J.K. - From 1871 to 1879, Lord Ralea - from 1879 to 1884, Thomson J.J. - from 1884 to 1919, Rutherford E. - from 1919 to 1937, Brang L. - from 1938 to 1953; Deputy Director in 1923-1935 - Changer J.

Scientific experimental studies were conducted by one scientist or a small group in the atmosphere of creative search. Lawrends Bragg recalled later about his work in 1913 together with his father, Henry Bragg: "It was a wonderful time when new exciting results received almost every week, like the discovery of new golden areas, where nuggets can be selected directly from the ground. It continued until The beginning of the war *) who stopped our joint work. "

3. Electron opening methods:

3.1.Trom Thomson

Joseph John Thomson Joseph John Thomson, 1856-1940

English physicist, more famous just like J. J. Thomson. Born in Chhetham Hill, suburb of Manchester, in the Bucinist-Antikvara family. In 1876 he won a scholarship for training in Cambridge. In 1884-1919, Professor of the Department of Experimental Physics of the Cambridge University and part-time is the head of the Cavendish Laboratory, which turned into one of Thomson's efforts to one of the most famous research centers of the world. At the same time in 1905-1918 - Professor of the Royal Institute in London. The laureate of the Nobel Prize in 1906 physics with the wording "For the study of the passage of electricity through gases", which, naturally, includes the opening of an electron. Thomson Son George Pajt Thomson, 1892-1975) also became over time Nobel laureate In physics - in 1937 for the experimental discovery of the diffraction of electrons on crystals.

In 1897, the young English physicist J. J. Thomson became famous in the eyelids as an electron discoverer. In his experience, Thomson used an improved cathode-ray tube, the design of which was supplemented with electric coils created (according to the AMPER's law) inside the tube magnetic field, and a set of parallel electrical capacitor plates that created an electric field inside the tube. Due to this, it became possible to investigate the behavior of cathode rays under the influence and magnetic, and electric field.

Using a new design tube, Thomson successively showed that: (1) cathode rays are deflected in a magnetic field in the absence of electric; (2) Cathodic rays are deflected in the electric field in the absence of magnetic; and (3) with the simultaneous action of electrical and magnetic fields of a balanced intensity oriented in directions, causing separately deviations in opposite sides, cathode rays spread straightforwardly, that is, the action of two fields is mutually bated.

Thomson found out that the relationship between electric and magnetic fields, in which their action is balanced, depends on the speed with which the particles are moving. After measuring, Thomson was able to determine the speed of the cathode rays. It turned out that they move significantly slower the speed of light, from which it should be that cathode rays can only be particles, since any electromagnetic radiation, including the light itself, propagates with the speed of light (see the electromagnetic radiation spectrum). These unknown particles. Thomson called "corpuscles", but soon they began to be called "electrons".

Immediately it became clear that the electrons are obliged to exist as part of atoms - otherwise, where did they come from? April 30, 1897 - the date of the report Thomson they received results at the meeting of the London Royal Society - is considered the birthday of an electron. And on this day, it was deposited into the past idea of \u200b\u200bthe "indivisibility" of atoms (see the atomic theory of the structure of the substance). Together with the discovery of the atomic nucleus that followed in ten with a small years (see Rangeford's experience) The opening of an electron laid the foundation of the modern atom model.

The "cathode" described above, or rather, the electron-ray tubes became the simplest predecessors of modern television kinescops and computer monitors, in which strictly controlled amounts of electrons are knocked out from the surface of the hot cathode, under the influence of variables of magnetic fields are deflected under strictly specified angles and bombard phosphorevating screens cells. By forming a clear image that arises as a result of a photoelectric effect, the discovery of which would also be impossible without our knowledge of the true nature of the cathode rays.

3.2. Specific Rutherford

Ernest Rutherford, Baron Rutherford Nelsonsky I Ernest Rutherford, First Baron Rutherford of Nelson, 1871-1937

New Zealand physicist. Born in Nelson, in the family of an artisan farmer. Won a scholarship for education at the University of Cambridge in England. After his end, he received an appointment to the Canadian University of McIl (McGill University), where in conjunction with Frederick Soddy (Frederick Soddy, 1877-1966) established the basic laws of the phenomenon of radioactivity, for which in 1908 was awarded the Nobel Prize in Chemistry. Soon the scientist moved to the University of Manchester, where under his leadership Hans Geiger (Hans Geiger, 1882-1945) invented his famous heiger counter, engaged in the study of the structure of the atom and in 1911 opened the existence of the atomic nucleus. During the First World War, he was engaged in the development of Sonarov (acoustic radars) to detect the enemy submarines. In 1919, he was appointed professor of physics and director of the Cabinder University of Cambridge and, in the same year, opened the decay of the kernel as a result of the bombardment with heavy high-energy particles. In this post, Rutherford remained until the end of his life, at the same time being the president of the Royal Scientific Society over the years. He was buried in Westminster Abbey next to Newton, Darwin and Faraday.

Ernest Rutherford - a unique scientist in the sense that he made his main discoveries after receiving the Nobel Prize. In 1911 he managed an experiment, who not only allowed scientists to look deep into atom and get an idea of \u200b\u200bits structure, but also became a sample of the grace and depth of the plan.

Using a natural source of radioactive radiation, Rutherford has built a gun that has given a directional and focused flow of particles. The gun was a lead box with a narrow slot, the radioactive material was placed inside. Due to this, the particles (in this case, the alpha particles, consisting of two protons and two neutrons), emitted by the radioactive substance in all directions, except for one, were absorbed by the lead screen, and only a directional bunch of alpha particles flew through the slot.

Scheme of experience

Next, on the path of the bundle, there were still several lead screens with narrow slits that cut the particles deviating from strictly

specified direction. As a result, the ideally focused bunch of alpha particles was parted to the target, and the target itself was the finest leaf of gold foil. Alpha-beam hit it. After the collision with the foil atoms, the alpha particles continued their way and fell to the luminescent screen installed behind the target, in which the alpha particles were recorded when the alpha particles were recorded. For them, the experimenter could be judged, in what amount and how much alpha particles deviate from the direction of the straight line as a result of collisions with foil atoms.

Rutherford, however, noticed that none of his predecessors had not even tried to check experimentally, whether some alpha particles are deflected at very large angles. The mesh model with raisins simply did not allow existence in the atom as dense and heavy elements of the structure that they could deflect the rapid alpha particles on significant angles, so no one was concerned about checking this opportunity. Rutherford asked one of his students to convert the installation in such a way that the scattering of alpha particles can be observed at large deviation angles - just to clean the conscience to finally eliminate such an opportunity. As a detector, a coated screen was used from sodium sulfide - material that gives a fluorescent flash when alpha particles get into it. What was the surprise of not only a student who directly conducted the experiment, but also the Rostford himself, when it turned out that some particles deviate to the corners up to 180 °!

The picture of the atom drawn by Rutherford according to the results of the experience, we are familiar well today. An atom consists of a superphoto, compact kernel carrying positive charge, and negatively charged light electrons around it. Later, scientists led to this picture a reliable theoretical base (see boron atom), but it all began with a simple experiment with a small sample of radioactive material and a piece of gold foil.

3.2.Method MILLIKEN

3.2.1. Short biography:

Robert Milliekin was born in 1868 in Illinois in the poor family of the priest. His childhood passed in the provincial town of McWaple, where much attention was paid to sports and taught poorly. Director of High School, who taught physics, spoke, for example, to his young listeners: "How can it be from the waves to do sound? Erunda, boys, all this nonsense! "

In the Oberdin college was no better, but Milli Cenu, who did not have material support, had to teach physics in high school himself. In America, then there were only two textbooks on physics, translated from French, and a talented young man did not provide difficulties to study them and successfully conduct classes. In 1893, he enters the University of Columbia, then rides to study in Germany.

Millilen was 28 years old when he received a proposal from A. Maykelson to take the place of the assistant in the University of Chicago. At the beginning, he was engaged in almost extremely pedagogical work here and only in the forty years began scientific research, which brought him world glory.

3.2.2. The first experiments and solving problems:

The first experiments were reduced to the following. Between the plates of the flat capacitor to which the voltage of 4000 V was served, a cloud was created, which consisted of water droplets, located on ions. At first there was a drop in the top of the cloud in the absence of an electric field. Then the cloud was created at the voltage turned on. The fall of the cloud happened under the action of the strength of gravity and electric power.
The ratio of force acting on a drop in the cloud, to the speed, which it acquires, is equally in the first and in the second case. In the first case, the force is equal to Mg, in the second Mg + Qe, where Q is the charge of the drop, e is the electric field strength. If the speed in the first case is equal to υ 1 in the second 2, then

Knowing the dependence of the rate of falling the cloud υ from the viscosity of the air, one can calculate the desired charge Q. However, this method did not give the desired accuracy, because it contained hypothetical assumptions that are not amenable to the control of the experimenter.

To increase the accuracy of measurements, it was necessary to first find a method for taking into account the evaporation of the cloud, which inevitably happened during the measurement process.

Reflecting on this problem, Milliken and came to the classical droplet method, which opened a number of unexpected possibilities. The history of the invention will provide to tell the author:
"Conscious that the speed of evaporation of the drops remained unknown, I tried to think of a way that would fully eliminate this indefinite value. My plan consisted in the following. In previous experiments, the electric field could only increase or reduce the rate of falling the top of the clouds under the action of gravity. Now I wanted to strengthen this field so that the upper surface of the cloud remains at a constant height. In this case, it was possible to accurately determine the rate of evaporation of the cloud and take it into account when calculating ".

To implement this idea, Millykein constructed a small battery in the dimensions, which produced voltage up to 10 4 V (for that time it was an outstanding achievement of the experimenter). She had to create a field, strong enough so that the cloud was kept as "Magomet Coffin", in suspended state. "When everything was ready for me," says Milliekin, and when a cloud was formed, I turned the switch, and the cloud turned out to be in the electric field. And at that moment, it melted on my eyes, in other words, it was not left of the cloud and a small piece, which could be observed with the help of a control optical device, as Wilson did and was going to do. How I first seemed to see the disappearance of the cloud in the electric field between the upper and lower plates meant that the experiment ended to no avail ... "However, as it often happened in the history of science, the failure gave rise to new idea. She led to the famous droplet method. "Repeated experiments - Milliken writes," showed that after scattering the clouds in a powerful electric field in its place it was possible to distinguish several separate water droplets. "(Stressed me. - V. D.). The "unsuccessful" experience led to the opening of the ability to keep in equilibrium and observe individual droplets for quite a long time.

But during the observation, the mass of water drops has changed significantly as a result of evaporation, and Milliekin after multi-day searches passed to experiments with drops of oil.

The experiment procedure was simple. The adiabatic expansion between the plates of the capacitor is formed cloud. It consists of droplets having various modulo and charge sign. When the electric field is turned on, having charges, the same name with the charge of the upper plate of the capacitor, are rapidly falling, and the drops with the opposite charge are attracted by the top plate. But a certain number of drops has such a charge that the force of gravity is equalized by electrical strength.

After 7 or 8 minutes. The cloud is dispersed, and a small number of drops remain in sight, the charge of which corresponds to the specified equilibrium of forces.

Milliekin observed these drops in the form of clear bright dots. "The history of these droplets is commonly so," he writes. "In the case of a small prevalence of gravity over the power of the field, they begin to slowly fall, but since they gradually evaporate, their descending movement will soon cease, and they become fixed for quite a long time. . Then the field begins to prevail, and the drops begin to slowly climb. Under the end of their life in space between the plates, this ascending movement becomes very strongly accelerated, and they are attracted at high speed to the upper plate. "

3.2.3. Installation Description:

The installation scheme is millilein, with the help of which in 1909 the decisive results were obtained, depicted in Figure 17.

In the chamber, a flat condenser was placed from round brass plates M and N with a diameter of 22 cm (the distance between them was 1.6 cm). In the center of the top plate there was a small hole p, through which droplets of oil passed. The latter have formed upon blowing the jet of oil with a sprayer. The air is pre-cleaned from dust by passing through a glass cotton tube. Oil drops had a diameter of about 10 -4 cm.

From the rechargeable battery in the capacitor plates, a voltage was fed 10 4. V. With the help of the switch, the plates could be shred and the electric field would destroy.

Drops of oils that fell between plates M and N were illuminated by a strong source. Perpendicular to the direction of the rays through the visual tube was observed the behavior of the drop.

The ions necessary for the condensation of the droplets were created by radiation a piece of radium weighing 200 mg, located at a distance from 3 to 10 cm on the side of the plates.

With the help of a special device lowering the piston, gas expansion was performed. After 1 - 2 s after the radium expansion, it was removed or leaving a lead screen. Then the electric field turned on and the droplet observation began. Viriving pipe. The pipe had a scale at which it was possible to count the path passed the drop in a certain period of time. The time was fixed at an exact clock with arrethir.

In the process of observations, Millique detected a phenomenon that served as the key to the entire series of subsequent accurate measurements of individual elementary charges.

"Working over suspended drops," Millilen writes, "I forgot them several times to close them from radium rays. Then I happened to notice that from time to time, one of the droplets suddenly changed his charge and began to move along the field or against him, obviously, capturing in the first case, and in the second case, a negative ion. This opened the opportunity to measure with the reliability of not only the charges of individual droplets, as I did until then, but also the charge of a separate atmospheric ion.

In fact, measuring the speed of the same drop twice, once before, and the second time after the capture of the ion, I obviously could completely eliminate the properties of the drops and the properties of the medium and operate with the value proportional to only the charge of the captured ion.

3.2.4. Elementary charge calculation:

The elementary charge was calculated by a milliken based on the following considerations. The speed of droplets is proportional to the power acting on it and does not depend on the drop of drops.
If the drop fell between the plates of the capacitor under the action of only gravity with the speed υ, then

When the field directed against the strength of gravity, the effective force will be the difference QE - Mg, where Q is the charge of the drop, e is the field strength module.

The speed of the drop will be equal to:

υ 2 \u003d k (QE-MG) (2)

If divided equality (1) on (2), we get

From here

Let the drop capture the ion and the charge was equal to q ", and the speed of movement υ 2. The charge of this captured ion is denoted by e.

Then E \u003d Q "- Q.

Using (3), we get

The value is constant for this drop.

3.2.5. Conclusions from the Method of Method

Consequently, every captured drop charge will be proportional to the speed difference (υ "2 - υ 2), in other words, proportional to the change in the speed of the drop due to the capture of the ion! So, the measurement of the elementary charge was reduced to the measurement of the path traveled, and the time for which this The path was passed. Numerous observations have shown the justice of formula (4). It turned out that the value of e can only change with jumps! Always observed charges E, 2e, 3E, 4E, etc.

"In many cases, it writes Milliekin," the drop was observed for five or six hours, and during this time she captured not eight or ten ions, and hundreds of them. In total, I observed this way by the capture of many thousands of ions, and in all cases a captured charge ... was either exactly equal to the smallest of all captured charges, or it was equal to a small whole multiple of this magnitude. This is a direct and irrefutable proof that the electron is not "statistical mean", but that all electrical charges on ions or exactly equal to the charge of an electron, or represent small entire multiple charges of this charge. "

So, atomistic, discreteness or, speaking modern tongueThe quantization of the electric charge has become an experimental fact. It was now important to show that the electron, so to speak, omnipresent. Any electrical charge in the body of any nature is the sum of the same elementary charges.

The Milliken method allowed unambiguously to answer this question. In the first experiments, the charges were created by ionization of neutral gas molecules with a flow of radioactive radiation. Measured charge of ions captured by drops.

When spraying the liquid, the drip pulverizer is electrified due to friction. It was well known in the XIX century. Are these charges are also quantized, like the charges of ions? Millilen "weighs" drops after spraying and produces charge measurements described above. The experience discovers the same discreteness of the electric charge.

By splashing oil drops (dielectric), glycerin (semiconductor), mercury (conductor), Millykein proves that charges on the bodies of any physical nature consist in all cases without exceptions from individual elementary portions of strictly constant values. In 1913, Milliecin summarizes the results of numerous experiments and gives the following value for an elementary charge: E \u003d 4.774. 10 -10 units. Charge SGSE. Thus was installed one of the most important constants of modern physics. The definition of an electric charge has been a simple arithmetic task.

3.4 Common visualization method:

A big role in strengthening the thought of the reality of the electron was played by the discovery of Ch.T.R. Wilson effect of condensation of water vapor on ions, which leads to the possibility of photographing the tracks of particles.

They say that A. Compton at the lecture could not convince the skeptical listener in the reality of the existence of microparticles. He told that she would believe, only seeing them to face them.
Then Compton showed a photo with a track of α-particles, next to which was a fingerprint. "Do you know what it is?" - asked Compton. "Finger", "answered the listener. "In this case," the compaton solemnly said, "this luminous band is a particle."
Photos of the tracks of electrons not only indicated the reality of electrons. They confirmed the assumption of the smallness of the sizes of electrons and allowed to compare the results of theoretical calculations with experience, in which the electron radius appeared. Experiments, the beginning of which was put on Lenard in the study of the penetrating ability of cathode rays, showed that very fast electrons emitted by radioactive substances give tracks in the gas in the form of direct lines. The length of the track is proportional to the electron energy. Photos of the tracks of α-particles of high energy show that tracks consist of a large number of points. Each point is a water droplet arising on ion, which is formed by the collision of an electron with an atom. Knowing the size of the atom and their concentration, we can calculate the number of atoms, through which the α-particle should be passed at a given distance. A simple calculation shows that the α particle must pass about 300 atoms before it comes on the way one of the electrons constituting the atom shell, and will produce ionization.

This fact convincingly indicates that the volume of electrons is a negligible share of the volume of the atom. The track of an electron having low energy is twisted, therefore, a slow electron is deflected by the intra-mattar field. It produces more ionization acts on its path.

From the theory of scattering, you can obtain data for estimating the deviation angles depending on the electron energy. This data is well confirmed when analyzing real tracks, the coincidence of the theory with the experiment strengthened an idea of \u200b\u200ban electron as the smallest particle of the substance.

Conclusion:

The measurement of elementary electric charge opened the possibility of accurately determining a number of essential physical constants.
Knowledge of the value of E automatically makes it possible to determine the value of the fundamental constant - constant Avogadro. The experiments of Millique existed only gross assessments of constant avogadro, which were given by the kinetic theory of gases. These estimates relied on the calculation of the average radius of the air molecule and fluctuated in fairly wide limits from 2. 10 23 to 20. 10 23 1 / mol.

Suppose that we are known for the Q, which passed through the electrolyte solution, and the amount of substance M, which was postponed on the electrode. Then, if the charge of the ion is ze 0 and its mass M 0, equality is performed.

If the mass of the laid substance is equal to one pray,

that Q \u003d f-constant Faraday, and F \u003d N 0 E, where:

Obviously, the accuracy of the definition of constant avogadro is defined by the accuracy with which the electron charge is measured. Practice required an increase in the accuracy of determining the fundamental constants, and this was one of the incentives to continue to improve the method of measuring the electrical charge quantum. This work that is already purely metrological nature continues until now.

The most accurate are currently values:

e \u003d (4.8029 ± 0.0005) 10 -10. units. Charge of SGSE;

N 0 \u003d (6.0230 ± 0.0005) 10 23 1 / mol.

Knowing N O, you can determine the number of gas molecules in 1 cm 3, since the volume occupied by 1 mole of gas is the already known permanent value.

Knowledge of the number of gas molecules in 1 cm 3 gave in turn the ability to determine the average kinetic energy Thermal motion of the molecule. Finally, in charge of the electron, it is possible to determine a constant plank and constant Stefan-Boltzmann in the law of heat radiation.

Methodical remark. The electron is already known to students from the course of chemistry and the corresponding section of the VII class program. Now you need to deepen the idea of \u200b\u200bthe first elementary particle of the substance, remind the studied, tie with the first topic of the section "Electrostatics" and move to a higher level of interpretation of the elementary charge. It should be borne in mind the complexity of the concept of an electric charge. The proposed excursion can help the disclosure of this concept and penetrate the essence of the case.

Electron has a difficult story. To come to the target with the shortest way, it is advisable to keep a story as follows.

There were skeptics who generally ignored the opening of the electron. Academician A. F. Ioffe in memories of his teacher V. K. X-ray wrote: "Until 1906-1907. The word electron should not be pronounced in the Physical Institute of Munich University. X-ray considered it unproved hypothesis used often without sufficient grounds and without needs".

The electron has not come out of the framework of the "clean" science. Recall that the first electronic lamp appeared only in 1907

To move from faith to belief, it was necessary to insulate an electron, to invent the method of direct and accurate measurement of the elementary charge.

Such a task was solved by American physicist Robert Millique (1868-1953) in a series of subtle experiments that were started in 1906.

Robert Milliekin was born in 1868 in Illinois in the poor family of the priest. His childhood passed in the provincial town of McWaple, where much attention was paid to sports and taught poorly. The director of high school, who taught physics, spoke, for example, to his young listeners: "How can it be from the waves to make the sound? Nonsense, boys, all this nonsense!"

The ratio of force acting on a drop in the cloud, to the speed, which it acquires, is equally in the first and in the second case. In the first case, the force is equal to Mg, in the second Mg + Qe, where Q is the charge of the drop, e is the electric field strength. If the speed in the first case is equal to V 1 in the second V 2, then

Knowing the dependence of the rate of falling the cloud V from the viscosity of air, one can calculate the desired charge Q. However, this method did not give the desired accuracy, because it contained hypothetical assumptions that are not amenable to the control of the experimenter.

To increase the accuracy of measurements, it was necessary to first find a method for taking into account the evaporation of the cloud, which inevitably happened during the measurement process.

Reflecting on this problem, Milliken and came to the classical droplet method, which opened a number of unexpected possibilities. The history of the invention will provide to tell the author:

"Conscious that the speed of evaporation of the drops remained unknown, I tried to come up with a way that would completely eliminate this indefinite value. My plan consisted in the following. In previous experiments, the electric field could only increase or reduce the speed of the clouds' tip under the action of gravity. Now I wanted to strengthen the field so that the upper surface of the cloud remained at a permanent altitude. In this case, it was possible to accurately determine the rate of evaporation of the cloud and take it into account when calculating ". To implement this idea, Milliekin constructed a small battery with a battery, which produced voltage to 104 V (for that time it was an outstanding achievement of the experimenter). It was supposed to create a field, strong enough so that the cloud was kept as "Magomet Coffin", in suspended state.

"When everything was ready for me," says Milliekin, "and when a cloud was formed, I turned the switch, and the cloud turned out to be in the electric field. And at that moment it melted in my eyes, in other words, there was no little piece from my own cloud. which could be observed with the help of a control optical device, as Wilson did and was going to do. How I first seemed to see the disappearance of the cloud in the electric field between the upper and lower plates meant that the experiment ended to no avail ... "

However, as it often happened in the history of science, the failure gave rise to a new idea. She led to the famous droplet method. "Repeated experiments," says Milliekin, "showed that after scattering the clouds in a powerful electric field in its place it was possible to distinguish between several separate water drops" (I am stressed by me. - V. D.).

The "unsuccessful" experience led to the opening of the ability to keep in equilibrium and observe individual droplets for quite a long time.

But during the observation, the mass of water drops has changed significantly as a result of evaporation, and Milliekin after multi-day searches passed to experiments with drops of oil.

After 7 or 8 minutes, the cloud is dissipated, and a small number of drops remain in the field of view, the charge of which corresponds to the balance of the balance.

Milliekin observed these drops in the form of clear bright dots. "The story of these droplets is usually so," he writes. "In the case of a small prevalence of gravity over the power of the field, they begin to slowly fall, but since they gradually evaporate, their descending movement will soon cease, and they have become fixed for quite a long time. Then the field begins to prevail, and the drops begin to slowly rise. Under the end of their life in the space between the plates, this ascending movement becomes very highly accelerated, and they are attracted at high speed to the upper plate. "

The installation scheme is millilein, with the help of which in 1909 the decisive results were obtained, depicted in Figure 17.

From the rechargeable battery in the capacitor plates, a voltage was fed 104 V. With the switch, the plates could be shorted and the electrical field could be destroyed.

Drops of oils that fell between plates M and N were illuminated by a strong source. Perpendicular to the direction of the rays through the visual tube was observed the behavior of the drop.

The ions necessary for the condensation of the droplets were created by radiation a piece of radium weighing 200 mg, located at a distance from 3 to 10 cm on the side of the plates.

With the help of a special device lowering the piston, gas expansion was performed. After 1-2 s after the expansion of the radium was removed or leaving the lead screen. Then the electric field turned on and the drops of droplets began in the visual tube.

The pipe had a scale at which it was possible to count the path passed the drop in a certain period of time. The time was fixed at an exact clock with arrethir.

In the process of observations, Millique detected a phenomenon that served as the key to the entire series of subsequent accurate measurements of individual elementary charges.

"Working over weighted drops," writes Milliekin, "I forgot them several times from radium rays. Then I happened to notice that from time to time one of the droplets suddenly changed his charge and began to move along the field or against him, obviously capturing In the first case, a positive, and in the second case, a negative ion. It opened the opportunity to measure with reliability not only the charges of individual droplets, as I did until then, but also the charge of a separate atmospheric ion.

The elementary charge was calculated by a milliken based on the following considerations. The speed of droplets is proportional to the power acting on it and does not depend on the drop of drops.

If the drop fell between the capacitor plates under the action of only gravity with the speed V 1, then

When the field is turned on against the strength of gravity, the actual force will be the difference Q \u003d Mg, where Q is the charge of the drop, e is the field strength module.

The speed of the drop will be equal to:

v 2 \u003d k (QE - MG) (2)

If divided equality (1) on (2), we get

Let the drop capture the ion and the charge of it was equal to q 'and the speed of movement V 2'. The charge of this captured ion is denoted by e. Then E \u003d Q '- Q.

Using (3), we get

The value is constant for this drop.

Consequently, every captured drop charge will be proportional to the speed difference (V '2 -V 2), in other words, proportional to the change in the speed of the drop due to the capture of the ion!

So, the measurement of the elementary charge was reduced to the measurement of the path traveled, and the time for which this path was passed.

Numerous observations showed the justice of formula (4). It turned out that the value of e can only be changed with jumps! There are always charges E, 2e, 3E, 4E, etc.

"In many cases, Milliken writes," the drop was observed for five or six hours, and during this time she captured not eight or ten ions, and hundreds of them. In total, I observed this way by capturing many thousands of ions, and in all Cases captured ... was either exactly equal to the smallest of all captured charges, or it was equal to a small whole multiple of this value. This is a direct and irrefutable proof that the electron is not "statistical mean", but that all electrical charges on ions or exactly equal to the charge of an electron, or represent small whole multiple of this charge. "

So, atomistic, discreteness, or, in modern language, the quantization of the electric charge has become an experimental fact. It was now important to show that the electron, so to speak, omnipresent. Any electrical charge in the body of any nature is the sum of the same elementary charges.

The Milliken method allowed unambiguously to answer this question.

In the first experiments, the charges were created by ionization of neutral gas molecules with a flow of radioactive radiation. Measured charge of ions captured by drops.

When spraying the liquid, the drip pulverizer is electrified due to friction. It was well known in the XIX century. Are these charges are also quantized, like the charges of ions?

Millilen "plays" drops after splashing and produces charge measurements described above. The experience discovers the same discreteness of the electric charge.

In 1913, Milliecin summarizes the results of numerous experiments and gives for an elementary charge the following insertion: E \u003d 4,774 · 10 -10. Charge SGSE.

Thus was installed one of the most important constants of modern physics. The definition of an electric charge has been a simple arithmetic task.

Visualization of electrons. A big role in strengthening the thought of the reality of an electron was played by the discovery of G. A. Wilson effect of condensation of water vapor on ions, which led to the possibility of photographing particles tracks.

They say that A. Compton at the lecture could not convince the skeptical listener in the reality of the existence of microparticles. He told that she would believe, only seeing them to face them.

Then Compton showed photograph E a trac of α-particles, next to which was a fingerprint. "Do you know what it is?" - asked Compton. "Finger", "answered the listener. "In this case," the compaton declared solemnly, "this luminous band is a particle."

Photos of electron tracks not only testified to the reality of electrons. They confirmed the assumption of the smallness of the sizes of electrons and allowed to compare the results of theoretical calculations with experience, in which the electron radius appeared. Experiments, the beginning of which was laid by Lenard in the study of the penetrating ability of cathode rays, showed that very fast electrons emitted by radioactive substances give tracks in the gas in the form of straight lines. The length of the track is proportional to the electron energy. Photos of trains of α-particles of high energy show that the tracks consist of a large number of points. Each point is a water droplet arising on ion, which is formed by the collision of an electron with an atom. Knowing the size of the atom and their concentration, we can calculate the number of atoms, through which the α-particle should be passed at a given distance. A simple calculation shows that an α-particle must pass about 300 atoms before it comes on the way one of the electrons constituting the atom shell, and will produce ionization.

This fact convincingly indicates that the volume of electrons is a negligible share of the volume of the atom. The electron track having low energy is twisted, therefore, a slow electron is deflected by an intra-mattable field. It produces more ionization acts on its path.

From the scattering theory, you can obtain data to estimate the deviation angles depending on the electron energy. This data is well confirmed when analyzing real tracks. The coincidence of the theory with the experiment strengthened an idea of \u200b\u200ban electron, as the smallest particle of the substance.

The measurement of elementary electric charge opened the possibility of accurately determining a number of essential physical constants.

Knowledge of the value of E automatically makes it possible to determine the value of the fundamental constant - constant Avogadro. The experiments of Millique existed only gross assessments of constant avogadro, which were given by the kinetic theory of gases. These estimates relied on calculating the average radius of air molecules and fluctuated in fairly wide limits of 2 · 10 23 to 20 · 10 23 1 / mol.

If the weight of the laid substance is equal to one pray, then Q \u003d F is a constant Faraday, with F \u003d N 0 E, from where N 0 \u003d F / E. Obviously, the accuracy of the definition of constant avogadro is defined by the accuracy with which the electron charge is measured.

The practice required an increase in the accuracy of the definition of fundamental constants, and this was one of the incentives to continue improving the method of measuring the electric charge quantum. This work that is already purely metrological nature continues until now.

The most accurate are currently values:

e \u003d (4,8029 ± 0.0005) 10 -10 units. Charge of SGSE;

N 0 \u003d (6.0230 ± 0.0005) 10 23 1 / mol.

Knowing n 0, you can determine the number of gas molecules in 1 cm 3, since the volume occupied by 1 mole of gas is the already known permanent value.

Knowledge of the number of gas molecules in 1 cm 3 gave the ability to determine the average kinetic energy of the heat movement of the molecule.

Finally, in charge of the electron, it is possible to determine a constant plank and constant Stefan-Boltzmann in the law of heat radiation.

Ministry of Education of the Russian Federation

Amur State Pedagogical University

Methods for determining elementary electric charge

Performed student 151g.

Venseliev A.A.

Checked: Cerantev TG

Introduction

1. Prehistory of the opening of an electron

2. Electron opening history

3. Experiments and methods of opening an electron

3.1.Trom Thomson

3.2. Specific Rutherford

3.3. Metility milliken

3.3.1. short biography

3.3.2. Installation Description

3.3.3. Calculation of elementary charge

3.3.4. Conclusions from the method

3.4. Common visualization method

Conclusion.

Introduction:

Electron - the first opening of the elementary particle in time; Material carrier of the least mass and the smallest electric charge in nature; Compound part of the atom.

Electron charge - 1,6021892. 10 -19 CL

4,803242. 10 -10 units. SGSE

Electron mass 9,109534. 10 -31 kg

Specific charge E / M E 1,7588047. 10 11 CL. kg -1.

Electron spin is 1/2 (in units H) and has two projections ± 1/2; Electrons subordinate to Fermi Dirac statistics, fermions. They have the principle of ban on Pauli.

The magnetic moment of the electron is - 1.00116 m b, where m b - magneton boron.

Electrical particle electron. According to experimental data, T E\u003e 2 lifetime. 10 22 years old.

1. Customer opening

2. Electron discretion:

If you distract from the fact that it was preceded by the opening of the first elementary particle - an electron, and from what happened to this outstanding event, it is possible to say briefly: in 1897, the famous English physicist Thomson Joseph John (1856-1940) measured the specific charge Q / M Cathodic-radial particles - "corpuscles", as he called them, to deviate cathode rays *) in electrical and magnetic fields.

3. Electron opening methods:

3.1.Trom Thomson

Joseph John Thomson Joseph John Thomson, 1856-1940

English physicist, more famous just like J. J. Thomson. Born in Chhetham Hill, suburb of Manchester, in the Bucinist-Antikvara family. In 1876 he won a scholarship for training in Cambridge. In 1884-1919, Professor of the Department of Experimental Physics of the Cambridge University and part-time is the head of the Cavendish Laboratory, which turned into one of Thomson's efforts to one of the most famous research centers of the world. At the same time in 1905-1918 - Professor of the Royal Institute in London. The laureate of the Nobel Prize in 1906 physics with the wording "For the study of the passage of electricity through gases", which, naturally, includes the opening of an electron. Thomson's son George Paget Thomson, 1892-1975 also became the Nobel laureate in physics - in 1937 for the experimental discovery of the diffraction of electrons on crystals.

Pashina Anna, Sevalnikov Alexey, Luzyanin Roman.

Purpose of work: learn to determine the value of the elementary charge by the method of electrolysis;explore methods for determining the chargeelectron.

Equipment: cylindrical vessel with copper sulfate solution, lamp, electrodes, scales, ammeter, constant voltage source, retain, clock, key, connecting wires.

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Laboratory work Definition of elementary charge by the electrolysis method was performed by students of the Chuchkovskaya SOSH 10 grade: Pashina Anna, Sevalnikov Alexey, Luzyanin Roman. Leader: Teacher Physics Chekalina O.Yu.

Objective: Learn to determine the value of the elementary charge by the electrolysis method; Examine the methods of determining the charge of an electron. Equipment: a cylindrical vessel with a copper sulfate solution, a lamp, electrodes, scales, an ammeter, a constant voltage source, a row, clock, key, connecting wires.

We collected a chain: work move:

The result of our work

We learned to determine the value of the elementary charge by the electrolysis method, studied the methods of determining the charge of an electron. Output:

V. Ya. Bryusov "Electron World" can be, these electrons are worlds, where five continents, art, knowledge, wars, thrones and the memory of forty-centuries! More, perhaps, every atom is the Universe, where one hundred planets; There everything here, in the volume compressed, but also what is not here. Their measures are small, but all the same their infinity, as here; There, sorrow and passion, like here, and even there the same world surge. Their wise men, their world of endless putting in the center of being, hurry to penetrate the sparks of secrets and know how now I am; And in the moment, when the currents of new forces are worked out of the destroyer, shout, in the dreams of self-sufficiency that God has fading his Svetoka!

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