Free electrons in metals. Extraordinary bricks

Where do the electrons come from when an electrical generator produces electricity? Is this from the air? Will the generator work in a vacuum? Electrons have mass, so where can you get them out if there is nothing?

KDN

Yes. The electrons that are responsible for the currents from the generator are free electrons in the wires themselves; all solid matter is partially made of electrons, so if you have a generator, you have a lot of electrons.

Answers

Anna V

It is possible to obtain electrons (negative charges) and positive ions in static electricity. This clearly shows that neutral atoms are not indivisible. Friction can provide the force to extract electrons and leave ions with a positive charge, as often happens when walking on carpets.

Faraday disk, the first electric generator. A horseshoe magnet (A) created a magnetic field through a disk (D). When the disc was turned, it caused an electrical current to flow radially outward from the center to the rim. The current flowed through the sliding spring contact m, through the external circuit and back to the center of the disk through the axis.

it is the electrons in metals that are driven by magnetic forces in the design, again separating the charges into electron motion and positive ions. Metals have very loosely bound electrons, which collectively belong to the Fermi sea and can generate electrical generator current.

So the answer is: atoms supply electrons from their outer electron shells. It's the atoms in the generator that supply the electrons, and yes, it will work in a vacuum.

Lahiru Perera

Just like your water pump doesn't generate water, an electric generator doesn't generate electrons, it simply moves electrons from one place to another.

Manishearth ♦

Currently your answer is not very helpful and it is much smaller than previous answers. Perhaps you could clarify this?

Jerry Schirmer

A conductive material is a material through which electrons can flow freely.

Voltage is the difference in electrical potential energy per unit of charge - if I have a 10V source and I give +1C of charge flowing from the positive terminal to the negative terminal, I will transfer 10J of energy to that charge. An electrical generator generates a potential difference between two terminals (usually either DC voltage or AC voltage). In normal household appliances, this voltage is connected to a wire, and the electrons in the conducting wire are what the potential energy in the battery is transferred to.

To the question Where do electrons come from in a conductor? Why don’t they run out, since the number of electrons in an atom is limited? given by the author Alexander Vladislavovich the best answer is You've probably heard more than once that metals have "free" electrons. So, “free” electrons are not entirely correct. In fact, they are not entirely free. Let's look at a copper conductor, let's say a ring of copper wire. Each copper atom consists of a nucleus with a charge of (+29) and 29 electrons (each with a charge of (-1)). These electrons are not the same; they are distributed across energy levels. The electronic formula of copper is 1s2 2s2 2p6 3s2 3p6 3d10 4s1. Electrons located at the energy levels 1s2 2s2 2p6 3s2 3p6 3d10 are held by the nucleus quite firmly and are each located near their “own” nucleus, but the electron located at the energy level 4s1 is held very weakly. Figuratively speaking, it is enough to “blow” not to tear it off completely, but to move it from one core to another. That other nucleus will have an extra electron, but it (the nucleus) cannot retain the extra electron and transfers it to the third, the next, etc. This transfer of electrons in the absence of external forces is chaotic, without a definite direction. In the end, this extra electron will come to the nucleus from which we “blowed it away”. Thus, electrons located at the 4s1 energy levels of all atoms constantly and very easily move from one atom to another. It is in this sense that they are called free.
Now consider the same copper ring, one section of which is placed in a magnetic field and, under the action of an external (mechanical) force, moves in it across the magnetic field lines (this part of the ring is a generator, and the remaining parts are wires and a consumer, for example a light bulb). In fact, if you go down to the atomic level, nuclei and electrons move under the influence of applied mechanical force. According to the law, I don’t remember who (I have completely forgotten physics) charges moving in a magnetic field are acted upon by a force that is directed perpendicular to the direction of movement of the conductor as a whole. This force cannot cause the nuclei (they are very heavy) and the electrons associated with them to move, located at the energy levels 1s2 2s2 2p6 3s2 3p6 3d10. But it forces the so-called “free electrons” (at the 4s level) to move along the conductor. Now the movement of “free” electrons is not chaotic, but strictly directed. An electron from the first atom moves to the second, from the second to the third, from the third... and so on. Finally, the electron from the last atom moves to the first (do not forget that our conductor is coiled into a ring.
Thus, each copper atom again has 29 electrons, but the 4s electrons are not their own, but from their neighbor. At the next moment of time, all “free” electrons will shift another 1 position in the same direction. The operation of alternating current generators is organized in such a way that, roughly speaking, the frame with current rotates in a constant magnetic field (in industrial ones with a frequency of 50 hertz). Therefore, in the first half of the revolution, the conductor (one side of the frame) crosses the lines of force near the north pole of the magnet, and the electrons move in one direction. During the second half of the frame's revolution, the conductor in question crosses the lines of force near the south pole of the magnet, and the electrons move in the opposite direction, and so on 50 times per second. True, in fact, the intensity of the magnetic field that the conductor crosses is not constant, but varies along a sinusoid, but this does not change the essence of what is happening. The result is an alternating electric current, i.e. the electrons actually do not go far from their nuclei, but “dangle” back and forth, as if on a swing. Something like this. Thank you very much, I’ve been tormented by this question all my life.
However, I did not understand how then all sorts of Tesla transformers distribute electricity in the air, or the same lightning, or the air also transmits these “free” electrons, but in this case they will not be able to return to the source, because there is no circuit.
In general, I would like to ask you, or can you recommend some literature?

Answer from Dr. Dick[guru]
so in place of those who left, others come. Current flows only in a closed circuit, remember? That is, electrons circulate in a circle

Answer from Alexander Shevchenko[active]
electrons do not run anywhere, they remain in place, they transfer charge along the chain to each other.

Answer from Pinochet[guru]
Let these electrons not run anywhere.
If I tell you that not a single scientist knows exactly what e-mail is. current, then you will lose faith in humanity.))
There are only hypotheses, that is, assumptions, so that somehow it is possible to make calculations.
And you can come up with a bunch of hypotheses yourself.
The electrons don’t run anywhere, they just beat each other in the ass to see who flies farthest.
Kind of like the balls in billiards.
And when should they run? -The speed of current is equal to the speed of light. They simply transfer charge to each other and that’s all.

Answer from Potato dad[guru]
free electrons.
They do not end because electric current is always a closed circle process. If something has left, something has arrived.

Answer from Globe[guru]
I don't know what the phrase "electrons transfer charge" means, but in my humble understanding this is the case.
When we flip a switch, a disturbance travels through the conductor at the speed of light. You've probably seen a freight train leaving the station? The locomotive pulls the first car, which pulls the second, and so the clanging of the automatic coupler sweeps along the entire chain (and the speed of this clanging is much higher than the speed of both the locomotive and the cars). So it is here - electrons rush to the plus, neighboring ones move in their place, etc. An electromagnetic pulse runs through a conductor at the speed of light.
Let us further remember that current strength is the charge that passes through a certain cross-section of a conductor per unit time. The speed of an individual electron may be tiny - but it crossed this cross section, and, therefore, made its contribution to the current.
There are a lot of free electrons in a conductor: approximately 10^23 (on the order of Avogadro’s constant). And although the charge of one electron is about 10^-19 C, it is enough for 0.01% of all electrons to start moving - and a current of 1A will flow through the conductor.
This is with constant current. In a variable, everything is even simpler - there the electrons can not move anywhere, but simply oscillate in accordance with the periodic change in the direction of the electric field.
And finally, about the decline. If there are fewer electrons in the conductor, then it will become positively charged, and either the current will stop, or it will begin to attract electrons from the minus of the battery.

Answer from Gennady Karpov[guru]
The electrons are running and running.
And the electric field makes them run.
An electron has a charge and moves under the influence of an elfield.
In conductors (metals, for example, in electrolytes, semiconductors.... a slightly different picture) due to the peculiarities of their structure, there are free electrons.
Some run away, and others come running in their place, from another conductor connected (for example, a switch when turned on). That conductor is connected to a current source, and the source drives them in a circle.
This happens with constant current.
If the current is alternating (remember about 50 Hz in the network), then they oscillate “this way and that” 50 times per second. And they remain almost in place.
The electric field in a conductor propagates quickly, at the speed of light (speed of propagation of the electric field). And the electrons themselves travel much slower.

Answer from Evgeny M.[guru]
When something runs in a circle, it never decreases.
Why didn’t such a simple thought occur to you? (Or your teacher?)
The mechanism of the process is not at all important, the details are not at all important. For example, it does not matter whether one specific electron manages to fly around the entire conductor along a closed path and return back, or whether it only flies into a neighboring atom and takes the place of the emitted electron there.
The main thing is that direct current ALWAYS flows only along a closed path. If the path is not closed, then the current always stops (electrons run out).
If the path is not closed, then only alternating current can exist in such a system. (For example, the path can be broken by a capacitor.) With alternating current, electrons generally do not fly away anywhere. They are located close to their atoms and only perform oscillatory movements at the frequency of alternating current.

Answer from Doctor[guru]
There are electrons in a conductor - they are in orbitals around the nuclei of atoms. But in conductors they are free. This means that under the influence of external forces they can move without hindrance. . They are on their own.
When an electric field arises, they begin to move in an orderly manner.
According to Kirkhoff's law, the sum of the currents is zero. That's why they don't end - they aren't wasted anywhere - but go around in circles in a closed chain.
Second, there are no orbits in atoms)
There are orbitals - a set of points where the location of the electron is more likely. You are using an old model of the boron atom.

Answer from MwenMas[guru]
In short, electrons do not escape from a conductor. They always remain in it and move under the influence of an electric field, either in one direction with direct current, or back and forth with alternating current. Imagine that in a heating system the pump drives water, but it doesn’t go anywhere, it doesn’t get smaller. Same with electrons.

Answer from Oriy Semykin[guru]
The resurrection of Einstein is for biologists and doctors.
There is no need for physics here, just common sense to figure it out. Electrons do not disappear, but only shift. Otherwise, a section of the circuit would quickly become positively charged. Since it remains neutral, the charge is compensated. It is clear that they are electrons. In reality, electrons do not “flow” in the form of a current, but an electromagnetic wave moves. This will be more difficult to understand.

Answer from Alex[newbie]
And to all that has been said, how is the charge (energy) of electrons renewed in a closed circuit, given that part of the energy is spent on heat during the operation of the consumer?

Answer from Maxim Diamonds[guru]
There is a word called resonance...

Answer from Yergey[active]
Science is unable to explain many phenomena using electron theory. These include the manifestation and disappearance of static electricity, the phenomenon of magnetism, the neutrality of the conductor, conductivity and non-conductivity of electric current substances, the piezoelectric effect, the presence of electric current in an open circuit, the absence of positrons in the generation of electric current and their presence in the generation of electric discharge, the manifestation of dualism by particles and much more.

Answer from Yura Ezhov[newbie]
And if there is an incandescent light bulb in the circuit. It spends energy in light and heat, so it turns out that the electrons are charged and transfer the charge to the light bulb. So then where do they get a new charge? From a magnetic field? Or because they continue to kick themselves in a circle
?

Free electron model on Wikipedia
Look at the Wikipedia article about Free electron model

It’s always like this: if the gardener rejoices at the rain, the tourist curses this inopportune downpour. The sun is shining hotly - and again some people feel good, but others don’t. Alas, there is no ideal in the world, and it is impossible to please everyone.

Before the discovery of the neutron, physicists thought that the atomic nucleus consisted of protons and electrons. This greatly upset the theorists - their calculations did not make ends meet. But the experimenters who studied the radioactive beta decay of nuclei were completely calm. They didn't have to worry about where the electrons came from.

The appearance of the neutron turned everything upside down. Now the theorists rejoiced, because the neutron-proton model of the structure of the nucleus eliminated all their difficulties. But the joy faded and faded from one glance towards those who were engaged in the study of radioactivity. They demanded an answer to a single, but extremely difficult question: where do electrons come from during the beta decay of nuclei, if they are not there?

Is it really necessary to abandon such a wonderfully simple picture of the structure of the nucleus again and take a step back? Is it really possible, having finally seen clear horizons, to plunge again into the frightening abyss of incomprehensible facts that do not agree with each other?

The question posed point-blank is: where do electrons come from in the nucleus? - forced physicists to take a huge step forward. Perhaps no less serious than the step with the recognition of electrons.

Twenty-three centuries ago, Democritus endowed the world of atoms with the property of indivisibility and immutability. At the very end of the 19th century, physicists tore this label off atoms and, without hesitation, applied it to elementary particles! It was very difficult for physicists to imagine the bricks of matter without the usual calm and reliable label.

The founder of quantum mechanics, W. Heisenberg, was the first to solve the mystery of the nucleus. He suggested that a neutron in the nucleus could sometimes turn into a proton plus an electron and a neutrino. The proton remains in the nucleus, and the remaining “emerging” particles leave it. Externally, this transformation looks like radioactive beta decay.

So this is where electrons come from! For the first time, researchers of the microworld discovered the mutual convertibility of elementary particles.

A neutron, as it later turned out, lives outside the nucleus for no more than 12 minutes, decaying into a proton, electron and neutrino. Nothing like this happens with a free proton. But in a radioactive nucleus, the energy situation is such that even a stable proton can turn into a neutron, positron and neutrino. Based on the name of the elementary particle - the positron - this event in the life of a radioactive nucleus began to be called positron decay.

What is this new particle - a positron?

It is both new and as if it has been familiar to us for a long time. This is an exact copy of an electron, only with the opposite sign of the electric charge. It would seem that there is nothing to mention about it if it is needed only for a few words about the positron decay of nuclei.

But no. This particle plays a special role in the history of particle physics. The discovery of the positron opened the door to the world of antiparticles. It showed us another property of matter - its ability to transform from a weighty form into a form of energy!

It all started when, in 1931, a young theoretical physicist at Cambridge University, Paul Dirac, obtained an equation describing the motion of an electron. He soon discovered that this equation has two solutions, that is, in addition to the electron, it is suitable for describing one more particle. It turned out that this particle should be completely similar to an electron, but with a positive electric charge.

At that time - and this happened more than forty years ago - no one had heard of antiparticles, and the only particle with a positive charge known to physicists was the proton. But the proton, due to its large mass, did not answer the second solution of the Dirac equation.

At first it seemed that this was a purely mathematical curiosity. But all attempts to exclude the second solution led to nothing. One of two things: either Dirac’s theory is wrong, or a positively charged electron exists in nature.

Dirac's prediction was so unusual that even the greatest scientists did not immediately accept it. Landau, for example, only three decades later stated: “Who can argue that Dirac did more for science in a few years than everyone present in this room did in their entire lives?”

A year later, in 1932, a positron was discovered in cosmic rays. In the cloud chamber they found traces of particles that could only belong to an electron, but with a positive charge.

When studying cosmic rays using a cloud chamber, experimenters used a method proposed back in 1927 by the Soviet physicist D. Skobeltsyn. A cloud chamber was placed between the poles of an electromagnet. This made it possible not only to see the trace of an elementary particle, but also to measure the energy by its curvature in a magnetic field and determine the sign of the electric charge of a representative of the microworld flying through the chamber. In the photographs taken in the cloud chamber, it was clearly visible that the traces of the electron and positron were deflected in opposite directions.

Experience confirmed the theory. Twenty-eight-year-old Paul Dirac joined the list of Nobel Prize laureates.

After the discovery of the positron, the question arose: doesn’t every elementary particle have “anti-reflections”? Experimenters began searching for the antiproton in cosmic rays. The electron-positron pair allegedly confirmed Dirac's theory. But no, no, and the thought crept in about the exception made by nature specifically for these particles.

“The time interval between the prediction of the antiproton and its observation in 1955 was too long,” said academician Ya. Zeldovich, “and some theorists’ nerves could not stand it - in recent years, attempts have been made to build a theory without antiprotons.”

Only a quarter of a century after Dirac's prediction, a group of American scientists led by Emilio Segre and Owen Chamberlain discovered the antiproton. And a year later they found an antineutron.

Grasping the positron end, physicists first slowly, and then faster and faster, began to pull out the net with antiparticles. And now no one doubts that each elementary particle has its own shadow - a corresponding antiparticle.

Studying traces of positrons in a cloud chamber, physicists immediately discovered that an electron and a positron, meeting each other, are mutually “destroyed” - annihilated.

There was nothing to fear for nature - it did not lose anything. The mass of both particles was transformed into another type of matter - into energy, the amount of which can be easily calculated using the well-known formula of Albert Einstein E = mc 2

“This result of modern physics,” wrote Nobel Prize laureate Max Laue, “is the most stunning of all that the development of natural science has ever brought.”

How strange the elementary bricks of matter turned out to be! Even such stable particles as the proton and electron could “disappear” along with their antiparticles. The thought involuntarily crept in: how could ancient rocks made of such fragile material survive to our time?

But the point is that elementary particles show readiness for transformations only in the specific conditions of radioactive nuclei and when meeting antiparticles. In the area of ​​the world accessible to us, there are immeasurably more stable nuclei than radioactive ones. And what saves us from annihilation is the absence of antiparticles in noticeable quantities.

The word "electron" in Greek means "amber".

Thales of Miletus (600 BC) noticed that if amber is rubbed hard against a cloth, it will begin to attract light objects. For quite a long time it was believed that only amber had this property. However, the same thing happens with objects made of plastic and other synthetic materials. You can easily observe this phenomenon with a comb and hair: after combing, the comb begins to attract hair (and the combed hair itself, please note, begins to repel each other).

The described phenomena are based on the phenomenon electricity . It consists in the interaction of microscopic particles with a charge - positive or negative. Particles with the same charge repel, and particles with opposite charges attract. Electrons- These are the smallest elementary particles with an electrical charge. The name electrons was given by the Englishman J. J. Stoney. He proposed to call an indivisible particle of charge this way.

As you already know, all substances consist of atoms - microscopic particles. Each atom, in turn, consists of a core and a shell. The core is formed by protons and neutrons, but the shell consists of electrons, and therefore is called electron cloud.

Not only electrons have an electric charge, but also protons (neutrons are electrically neutral, as their name suggests). In an atom, electrons are attracted to the nucleus because it has a positive charge due to the charge of protons, while electrons have a negative charge. But, despite these properties, electrons do not completely combine with the nucleus, since they are in constant motion. And the atom itself is completely electrically neutral, because in an atom the number of protons is equal to the number of electrons.

In metals, some electrons are not bound to atoms and can move freely. The directed movement of these electrons causes a phenomenon without which we can hardly imagine our lives - electric current. That's why metals are called conductors : they can conduct electricity. Substances that cannot conduct current are called insulators , or dielectrics .

Let's return to the beginning of our story and answer the question: why is amber electrified? First of all, note that only insulators can be electrified by friction. When two bodies rub together, some electrons transfer from one body to the other. As a result, the bodies acquire opposite charges. Only insulators can be electrified by friction, because only in these bodies do electrons that move from one body to another remain where they ended up. They begin to move freely in the conductors.

As you probably already guessed, the total charge of a pair of bodies that rubbed against each other is equal to zero, that is, such a floating electrically neutral.

Amber is electrified by friction very easily, just like ebonite, glass or cat fur.

This question is like cabbage, you open it up and open it up, but the “fundamental” stalk is still far away. Although the question apparently concerns this very stalk, you still have to try to overcome all the cabbage.

At the most superficial glance, the nature of current seems simple: current is when charged particles move. (If the particle does not move, then there is no current, there is only an electric field.) Trying to understand the nature of the current, and not knowing what the current consists of, they chose the direction for the current corresponding to the direction of movement of the positive particles. Later it turned out that an indistinguishable current, exactly the same in effect, is obtained when negative particles move in the opposite direction. This symmetry is a remarkable feature of the nature of current.

Depending on where the particles are moving, the nature of the current is also different. The current material itself is different:

• Metals have free electrons;
• In metal and ceramic superconductors there are also electrons;
• In liquids - ions that are formed during chemical reactions or when exposed to an applied electric field;
• In gases there are again ions, as well as electrons;
• But in semiconductors, electrons are not free and can move in a “relay race”. Those. It is not the electron that can move, but rather a place where it does not exist - a “hole”. This type of conductivity is called hole conductivity. At the junctions of different semiconductors, the nature of such current gives rise to effects that make all of our radio electronics possible.

Current has two measures: current strength and current density. There are more differences than similarities between the current of charges and the current of, for example, water in a hose. But such a view of the current is quite productive for understanding the nature of the latter. The current in a conductor is a vector field of particle velocities (if they are particles with the same charge). But we usually do not take these details into account when describing the current. We average this current.

If we take only one particle (naturally charged and moving), then a current equal to the product of charge and instantaneous speed at a particular moment of time exists exactly where this particle is located. Remember how it was in the song of the Ivasi duet “It’s time for a beer”: “... if the climate is difficult and the astral is hostile, if the train has left and all the rails have been TOOK UP...” :)

And now we come to that stalk that we mentioned at the beginning. Why does a particle have a charge (everything seems clear with movement, but what is a charge)? The most fundamental particles (now for sure:) seemingly indivisible) that carry a charge are electrons, positrons (antielectrons) and quarks. It is impossible to pull out and study an individual quark due to confinement; with an electron it seems easier, but it is also not very clear yet. At the moment, it is clear that the current is quantized: no charges are observed that are smaller than the charge of the electron (quarks are observed only in the form of hadrons with a total charge of the same or zero). An electric field separately from a charged particle can only exist in conjunction with a magnetic field, like an electromagnetic wave, the quantum of which is a photon. Perhaps some interpretations of the nature of electric charge lie in the realm of quantum physics. For example, the Higgs field predicted by her and discovered relatively recently (if there is a boson, there is a field) explains the mass of a number of particles, and the mass is a measure of how the particle responds to the gravitational field. Perhaps with charge, as a measure of response to an electric field, some similar story will be revealed. Why there is mass and why there is charge are somewhat related questions.

Much is known about the nature of electric current, but the most important thing is not yet known.