Does the proton have an electric charge? Proton charge - the basic quantity of elementary particle physics
Chapter 9. Elementary charges. Electron and proton
§ 9.1. Electromagnetic mass and charge. The question of the essence of charge
In Chapter 5, we found out the mechanism for the emergence of inertia, explained what “inertial mass” is and what electrical phenomena and the properties of elementary charges determine it. In Chapter 7 we did the same for the phenomenon of gravity and "gravitational mass". It turned out that both the inertia and gravity of bodies determine the geometric size elementary particles and their charge. Since the geometric size is a familiar concept, then at the heart of such fundamental phenomena as inertia and gravity, there is only one little-studied essence - “charge”. Until now, the concept of "charge" is mysterious and almost mystical. At first, scientists dealt only with macroscopic charges, i.e. charges of macroscopic bodies. At the beginning of the study of electricity in science, the concept of invisible "electric fluids" was used, the excess or deficiency of which leads to the electrification of bodies. For a long time, the debate was only about whether it was one liquid or two of them: positive and negative. Then it was found out that there are "elementary" charge carriers electrons and ionized atoms, i.e. atoms with an excess electron or a missing electron. Even later, the “most elementary” positive charge carriers, protons, were discovered. Then it turned out that there are many “elementary” particles and many of them have an electric charge, and this charge is always
is a multiple of some minimum detectable portion of the charge q 0 ≈ 1.602 10−19 C . This
portion and was called the "elementary charge." The charge determines the degree of participation of the body in electrical interactions and, in particular, electrostatic interactions. To date, there are no intelligible explanations of what an elementary charge is. Any reasoning on the topic that the charge consists of other charges (for example, quarks with fractional charge values) is not an explanation, but a scholastic “blurring” of the issue.
Let's try to think about the charges ourselves, using what we have already established earlier. Recall that the main law established for charges is Coulomb's law: the force of interaction between two charged bodies is directly proportional to the product of the magnitudes of their charges and inversely proportional to the square of the distance between them. It turns out that if we derive Coulomb's law from any specific physical mechanisms already studied, then we will thereby make a step in understanding the essence of charges. We have already said that elementary charges in terms of interaction with outside world are completely determined by their electric field: its structure and its motion. And they said that after the explanation of inertia and gravitation in elementary charges, nothing but a moving electric field remained. And the electric field is nothing but perturbed states of vacuum, ether, plenum. Well, let's be consistent and try to reduce the electron and its charge to a moving field! We already guessed in Chapter 5 that the proton is exactly like the electron, except for the charge sign and geometric size. If, by reducing the electron to a moving field, we see that we can explain both the sign of the charge and the independence of the amount of particle charge on the size, then our task will be completed, at least in the first approximation.
§ 9.2. Strange currents and strange waves. flat electron
To begin with, let's consider an extremely simplified model situation (Fig. 9.1) of a ring charge moving along a circular path of radius r 0 . And let him in general
electrically neutral, i.e. its center has a charge opposite in sign. This is the so-called "flat electron". We do not claim that the real electron is exactly like this, we are only trying to understand for the time being whether it is possible to obtain an electrically neutral object equivalent to a free elementary charge in a flat, two-dimensional case. Let's try to create our charge from the bound charges of the ether (vacuum, plenum). Let, for definiteness, the charge of the ring be negative, and the movement of the ring occurs clockwise (Fig. 9.1). In this case, the current I t flows counterclockwise. Select a small
ring charge element dq and assign to it a small length dl. It is obvious that at each moment of time the element dq moves with a tangential velocity v t and normal acceleration a n . With such a movement, we can associate the total current of the element dI -
vector value. This value can be represented as a constant tangential current dI t, constantly "turning" its direction with the flow
time, i.e. accelerated. That is, having normal acceleration dI& n . Difficulty
further consideration is due to the fact that so far in physics, mainly such alternating currents have been considered, whose acceleration lay on the same straight line with the direction of the current itself. In this case, the situation is different: current perpendicular to its acceleration. And what? Does this invalidate the previously firmly established laws of physics?
Rice. 9.1. Ring current and its force effect on the test charge
Just as the elementary current itself is associated with its magnetic field (according to the Biot-Savart-Laplace law), so the electric field of induction is associated with the acceleration of the elementary current, as we have shown in previous chapters. These fields have a force action F on the external charge q (Fig. 9.1). Since the radius r 0 is finite, the actions
elementary currents of the right (according to the figure) half of the ring cannot be fully compensated by the opposite action of the elementary currents of the left half.
Thus, between the ring current I and the external test charge q must
force interaction occurs.
As a result, we have obtained that we can speculatively create an object that, on the whole, will be completely electrically neutral in construction, but contain a ring current. What is ring current in vacuum? This is the displacement current. It can be represented as a circular motion of bound negative (or vice versa - positive) vacuum charges at complete rest of the opposing charges located
in center. It can also be represented as a joint circular motion of positive and negative bound charges, but with different speeds, or along different radii, or
in different sides... In the end, no matter how we look at the situation, it will
be reduced to a rotating electric field E , closed in a circle . This creates a magnetic field b, due to the fact that currents flow and an additional, unlimited cr at ohm electric field Eind associated with the fact that these currents accelerated.
This is exactly what we observe near real elementary charges (for example, electrons)! Here is our phenomenology of the so-called "electrostatic" interaction. It does not require free charges (with fractional or some other charge values) to build an electron. Just enough bound vacuum charges! Remember that by modern ideas the photon also consists of a moving electric field and is generally electrically neutral. If the photon is “bent” into a ring, then it will have a charge, since its electric field will now move not in a straight line and uniformly, but accelerated. Now it is clear how charges of different signs are formed: if the field E in the “ring model” (Fig. 9.1) is directed from the center to the periphery of the particle, then the charge is of one sign, if vice versa, then the other. If we open an electron (or a positron), we will create a photon. In reality, due to the need to preserve the moment of rotation, in order to turn a charge into a photon, you need to take two opposite charges, bring them together and get two electrically neutral photons as a result. Such a phenomenon (annihilation reaction) is indeed observed in experiments. So what is a charge? torque of the electric field! Next, we will try to deal with formulas and calculations and obtain Coulomb's law from the laws of induction applied to the case of alternating displacement current.
§ 9.3. Coulomb's law as a consequence of Faraday's law of induction
Let us show that in the two-dimensional (planar) approximation, the electron in the electrostatic sense is equivalent to the circular motion of the current, which is equal in magnitude to the charge current q 0 moving along the radius r 0 with a speed, equal speed light c.
To do this, we divide the total circular current I (Fig. 9.1) into elementary currents Idl, calculate dE ind, acting at the point where the test charge q, and integrate over the ring.
So, the current flowing in our case along the ring is equal to:
(9.1) I = q 0 v = q 0 c . 2 π r 0 2 π r 0
Since this current is curvilinear, that is, accelerated, then it is
variables:
I. Misyuchenko |
The last secret God |
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dt 2 r |
2πr |
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where a is the centripetal acceleration that each current element experiences when moving around a circle at speed c.
Substituting the expression known from kinematics for acceleration a = c 2 , we get: r 0
q0 c2 |
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2πr |
2 π r 2 |
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It is clear that the derivative for the current element will be expressed by the formula:
dl= |
q0 c2 |
dl . |
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2πr |
2 π r 2 |
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As follows from the Biot-Savart-Laplace law, each current element Idl creates an “elementary” magnetic field at the point where the test charge is located:
(9.5) dB = |
I[ dl , rr ] |
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From chapter 4 it is known that the alternating magnetic field of the elementary current generates an electric one:
(9.6) dE r = v r B dB r = |
μ 0 |
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I [dl, r] |
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Now let's substitute in this expression the value of the derivative of the elementary circular current from (9.4):
dl sin(β) |
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dE = |
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2 π r 2 |
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It remains to integrate these elementary electric field strengths along the current contour, that is, over all dl that we have identified on the circle:
q0 c2 |
sin(β) |
r 2 ∫ |
sin(β) |
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E = ∫ dE = ∫ 8 π |
2 π r 2 |
dl= |
16 π 2 ε |
dl . |
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It is easy to see (Fig. 9.1) that integration over angles will give:
(9.9) ∫ |
sin(β) |
4 r 2 |
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dl = 2 r0 |
r 2 0 |
r 2 0 . |
Accordingly, the total value of the electric field strength of induction E ind from our curvilinear current at the point where the test charge is located will be equal.
DEFINITION
Proton called a stable particle belonging to the class of hadrons, which is the nucleus of a hydrogen atom.
Scientists disagree on what scientific events should be considered the discovery of the proton. An important role in the discovery of the proton was played by:
- the creation by E. Rutherford of the planetary model of the atom;
- discovery of isotopes by F. Soddy, J. Thomson, F. Aston;
- observations of the behavior of the nuclei of hydrogen atoms when they are knocked out by alpha particles from nitrogen nuclei by E. Rutherford.
The first photographs of proton traces were obtained by P. Blackett in a cloud chamber while studying the processes of artificial transformation of elements. Blackett investigated the capture of alpha particles by nitrogen nuclei. In this process, a proton was emitted and the nitrogen nucleus was converted into an oxygen isotope.
Protons, together with neutrons, are part of the nuclei of all chemical elements. The number of protons in the nucleus determines the atomic number of the element in periodic system DI. Mendeleev.
A proton is a positively charged particle. Its charge is equal in modulus to the elementary charge, that is, the magnitude of the charge of the electron. The charge of a proton is often denoted as , then we can write that:
At present, it is believed that the proton is not an elementary particle. It has a complex structure and consists of two u-quarks and one d-quark. The electric charge of the u - quark () is positive and it is equal to
The electric charge of the d - quark () is negative and equal to:
Quarks bind the exchange of gluons, which are field quanta, they carry the strong interaction. The fact that protons have several point scattering centers in their structure is confirmed by experiments on the scattering of electrons by protons.
The proton has a finite size, which scientists are still arguing about. At present, the proton is represented as a cloud that has a blurred border. Such a boundary consists of constantly emerging and annihilating virtual particles. But in most simple tasks the proton, of course, can be considered a point charge. The rest mass of a proton () is approximately equal to:
The mass of a proton is 1836 times greater than the mass of an electron.
Protons take part in all fundamental interactions: strong interactions unite protons and neutrons into nuclei, electrons and protons combine in atoms with the help of electromagnetic interactions. We can cite, for example, the beta decay of a neutron (n) as a weak interaction:
where p is a proton; - electron; - antineutrino.
The decay of the proton has not yet been obtained. This is one of the important modern tasks of physics, since this discovery would be a significant step in understanding the unity of the forces of nature.
Examples of problem solving
EXAMPLE 1
Exercise | The nuclei of the sodium atom are bombarded with protons. What is the electrostatic repulsion force of a proton from the nucleus of an atom if the proton is at a distance m. Consider that the charge of the nucleus of the sodium atom is 11 times greater than the charge of the proton. The influence of the electron shell of the sodium atom can be ignored. |
Solution | We will take Coulomb's law as the basis for solving the problem, which can be written for our problem (assuming particles are point particles) as follows:
where F is the force of electrostatic interaction of charged particles; Cl is the proton charge; - the charge of the nucleus of the sodium atom; - vacuum permittivity; is the electrical constant. Using the data we have, we can calculate the desired repulsive force: |
Answer | H |
EXAMPLE 2
Exercise | Considering the simplest model of the hydrogen atom, it is believed that the electron moves in a circular orbit around the proton (the nucleus of the hydrogen atom). What is the speed of the electron if the radius of its orbit is m? |
Solution | Consider the forces (Fig. 1) that act on an electron moving in a circle. This is the force of attraction from the side of the proton. According to Coulomb's law, we write that its value is equal to ():
where = is the electron charge; - proton charge; is the electrical constant. The force of attraction between an electron and a proton at any point of the electron's orbit is directed from the electron to the proton along the radius of the circle. |
If you are familiar with the structure of the atom, then you probably know that the atom of any element consists of three types of elementary particles: protons, electrons, neutrons. Protons combine with neutrons to form an atomic nucleus. Since the proton has a positive charge, the atomic nucleus is always positively charged. of the atomic nucleus is compensated by the cloud of other elementary particles surrounding it. The negatively charged electron is the part of the atom that stabilizes the charge of the proton. Depending on which atomic nucleus surrounds, an element can either be electrically neutral (in the case of an equal number of protons and electrons in the atom), or have a positive or negative charge (in the case of a shortage or excess of electrons, respectively). An atom of an element that carries a certain charge is called an ion.
It is important to remember that it is the number of protons that determines the properties of the elements and their position in the periodic table. D. I. Mendeleev. Contained in atomic nucleus neutrons have no charge. Due to the fact that both protons are comparable and practically equal to each other, and the mass of an electron is negligible compared to them (1836 times less, then the number of neutrons in the nucleus of an atom plays a very important role, namely: determines the stability of the system and the speed of the nuclei. The content of neutrons is determined by the isotope (variety) of the element.
However, due to the discrepancy between the masses of charged particles, protons and electrons have different specific charges (this value is determined by the ratio of the charge of an elementary particle to its mass). As a result, the specific charge of the proton is 9.578756(27) 107 C/kg versus -1.758820088(39) 1011 for the electron. Due to the high value of the specific charge, free protons cannot exist in liquid media: they are amenable to hydration.
The mass and charge of the proton are specific quantities that were established at the beginning of the last century. Which scientist made this - one of the greatest - discovery of the twentieth century? Back in 1913, Rutherford, based on the fact that the masses of all known chemical elements are greater than the mass of a hydrogen atom by an integer number of times, suggested that the nucleus of a hydrogen atom is included in the nucleus of an atom of any element. Somewhat later, Rutherford conducted an experiment in which he studied the interaction of the nuclei of the nitrogen atom with alpha particles. As a result of the experiment, a particle flew out of the nucleus of the atom, which Rutherford called "proton" (from the Greek word "protos" - the first) and suggested that it was the nucleus of the hydrogen atom. The assumption was proved experimentally during the re-conducting of this scientific experiment in a cloud chamber.
The same Rutherford in 1920 put forward a hypothesis about the existence in the atomic nucleus of a particle whose mass is equal to the mass of a proton, but which does not carry any electric charge. However, Rutherford himself failed to detect this particle. But in 1932, his student Chadwick experimentally proved the existence of a neutron in the atomic nucleus - a particle, as predicted by Rutherford, approximately equal in mass to a proton. It was more difficult to detect neutrons, since they do not have an electric charge and, accordingly, do not interact with other nuclei. The absence of a charge explains such a property of neutrons as a very high penetrating power.
Protons and neutrons are bound in the atomic nucleus by a very strong interaction. Now physicists agree that these two elementary nuclear particles are very similar to each other. So, they have equal spins, and nuclear forces act on them in exactly the same way. The only difference is that the charge of the proton is positive, while the neutron has no charge at all. But since the electric charge in nuclear interactions does not matter, it can only be considered as a kind of label for the proton. If, however, to deprive the proton of an electric charge, then it will lose its individuality.
Until the beginning of the 20th century, scientists considered the atom to be the smallest indivisible particle of matter, but this turned out not to be the case. In fact, its nucleus with positively charged protons and neutral neutrons is located in the center of the atom, negatively charged electrons rotate around the nucleus in orbitals (this atom model was proposed in 1911 by E. Rutherford). It is noteworthy that the masses of protons and neutrons are almost equal, but the mass of an electron is about 2000 times less.
Although an atom contains both positively charged particles and negatively, its charge is neutral, because the atom has the same number of protons and electrons, and differently charged particles neutralize each other.
Later, scientists found that electrons and protons have the same amount of charge, equal to 1.6 10 -19 C (C - coulomb, a unit of electric charge in the SI system.
Have you ever thought about the question - what number of electrons corresponds to a charge of 1 C?
1 / (1.6 10 -19) \u003d 6.25 10 18 electrons
electrical force
Electric charges act on each other, which manifests itself in the form electrical force.
If a body has an excess of electrons, it will have a total negative electric charge, and vice versa - with a deficit of electrons, the body will have a total positive charge.
By analogy with magnetic forces, when like-charged poles repel, and oppositely charged poles attract, electric charges behave in a similar way. However, in physics it is not enough to talk simply about the polarity of the electric charge, its numerical value is important.
To find out the magnitude of the force acting between charged bodies, it is necessary to know not only the magnitude of the charges, but also the distance between them. Previously considered gravitational force: F = (Gm 1 m 2)/R 2
- m1, m2- masses of bodies;
- R- distance between the centers of bodies;
- G \u003d 6.67 10 -11 Nm 2 / kg is the universal gravitational constant.
As a result of laboratory experiments, physicists have derived a similar formula for the interaction force of electric charges, which is called Coulomb's law:
F = kq 1 q 2 /r 2
- q 1 , q 2 - interacting charges, measured in C;
- r - distance between charges;
- k - coefficient of proportionality ( SI: k=8.99 10 9 Nm 2 C 2 ; SGSE: k=1).
- k=1/(4πε 0).
- ε 0 ≈8.85·10 -12 C 2 N -1 m -2 - electrical constant.
According to Coulomb's law, if two charges have the same sign, then the force F acting between them is positive (the charges repel each other); if the charges have opposite signs, the acting force is negative (the charges are attracted to each other).
How huge in strength is a charge of 1 C can be judged using Coulomb's law. For example, if we assume that two charges, each in 1 C, are separated by a distance of 10 meters from each other, then they will repel each other with force:
F \u003d kq 1 q 2 / r 2 F \u003d (8.99 10 9) 1 1 / (10 2) \u003d -8.99 10 7 N
This is a fairly large force, approximately comparable to a mass of 5600 tons.
Now, using Coulomb's law, let's find out with what linear speed an electron rotates in a hydrogen atom, assuming that it moves in a circular orbit.
The electrostatic force acting on an electron, according to Coulomb's law, can be equated to the centripetal force:
F = kq 1 q 2 /r 2 = mv 2 /r
Taking into account the fact that the mass of an electron is 9.1 10 -31 kg, and the radius of its orbit = 5.29 10 -11 m, we obtain the value 8.22 10 -8 N.
Now you can find the linear velocity of the electron:
8.22 10 -8 \u003d (9.1 10 -31) v 2 / (5.29 10 -11) v \u003d 2.19 10 6 m / s
Thus, the electron of the hydrogen atom rotates around its center at a speed equal to about 7.88 million km/h.