Electricity — directed (ordered) motion of charged particles. Such particles can be: in metals - electrons, in electrolytes - ions (cations and anions), in gases - ions and electrons, in vacuum under certain conditions - electrons, in semiconductors - electrons and holes (electron-hole conductivity). Sometimes electric current is also called the displacement current resulting from a change in the electric field over time.

Electric current has the following manifestations:

• heating of conductors (there is no heat release in superconductors);
• change in the chemical composition of conductors (observed mainly in electrolytes);
• the creation of a magnetic field (manifested in all conductors without exception).

Classification:

If charged particles move inside macroscopic bodies relative to a particular medium, then such a current is called an electric conduction current. If macroscopic charged bodies are moving (for example, charged raindrops), then this current is called the convection current.

Distinguish variable(English alternating current, AC), constant(English direct current, DC) and throbbing electric currents, as well as their various combinations. In such terms, the word "electric" is often omitted.

D.C - current, the direction and magnitude of which change slightly with time.

Alternating current - current, the magnitude and direction of which change with time. In a broad sense, alternating current is any current that is not direct. Among the alternating currents, the main one is the current, the value of which varies according to a sinusoidal law. In this case, the potential of each end of the conductor changes with respect to the potential of the other end of the conductor alternately from positive to negative and vice versa, while passing through all intermediate potentials (including the zero potential). As a result, a current arises that continuously changes direction: when moving in one direction, it increases, reaching a maximum, called the amplitude value, then decreases, at some point becomes zero, then increases again, but in the other direction and also reaches the maximum value , falls off to then pass through zero again, after which the cycle of all changes resumes.

Quasi-stationary current - “a relatively slowly changing alternating current, for the instantaneous values ​​​​of which the laws of direct currents are satisfied with sufficient accuracy” (TSB). These laws are Ohm's law, Kirchhoff's rules and others. Quasi-stationary current, as well as direct current, has the same current strength in all sections of an unbranched circuit. When calculating quasi-stationary current circuits due to the emerging e. d.s. capacitance and inductance inductions are taken into account as lumped parameters. Quasi-stationary are ordinary industrial currents, except for currents in long-distance transmission lines, in which the condition of quasi-stationarity along the line is not satisfied.

High frequency alternating current - current, in which the condition of quasi-stationarity is no longer satisfied, the current passes over the surface of the conductor, flowing around it from all sides. This effect is called the skin effect.

Ripple current - a current in which only the magnitude changes, but the direction remains constant.

Eddy currents (Foucault currents) - “closed electric currents in a massive conductor that arise when the magnetic flux penetrating it changes”, therefore eddy currents are induction currents. The faster the magnetic flux changes, the stronger the eddy currents. Eddy currents do not flow along certain paths in the wires, but, closing in the conductor, form vortex-like contours.

The existence of eddy currents leads to the skin effect, that is, to the fact that the alternating electric current and magnetic flux propagate mainly in the surface layer of the conductor. Eddy current heating of conductors leads to energy losses, especially in the cores of AC coils. To reduce energy losses due to eddy currents, the alternating current magnetic circuits are divided into separate plates, isolated from each other and located perpendicular to the direction of eddy currents, which limits the possible contours of their paths and greatly reduces the magnitude of these currents. At very high frequencies, instead of ferromagnets, magnetodielectrics are used for magnetic circuits, in which, due to the very high resistance, eddy currents practically do not occur.

Characteristics:

Historically, it is accepted that the direction of the current coincides with the direction of movement of positive charges in the conductor. In this case, if the only current carriers are negatively charged particles (for example, electrons in a metal), then the direction of the current is opposite to the direction of movement of charged particles.

The speed of the directed motion of particles in conductors depends on the material of the conductor, the mass and charge of the particles, the ambient temperature, the applied potential difference, and is much less than the speed of light. In 1 second, the electrons in the conductor move by ordered movement by less than 0.1 mm. Despite this, the propagation speed of the actual electric current is equal to the speed of light (the propagation speed of the electromagnetic wave front). That is, the place where the electrons change their speed of movement after a change in voltage moves with the speed of propagation of electromagnetic oscillations.

Main types of conductors:

Unlike dielectrics, conductors contain free carriers of uncompensated charges, which, under the action of a force, usually a difference in electrical potentials, set in motion and create an electric current. The current-voltage characteristic (dependence of current strength on voltage) is the most important characteristic of a conductor. For metallic conductors and electrolytes, it has the simplest form: the current strength is directly proportional to the voltage (Ohm's law).

Metals - here the current carriers are conduction electrons, which are usually considered as an electron gas, clearly showing the quantum properties of a degenerate gas.

Plasma - ionized gas. Electric charge is carried by ions (positive and negative) and free electrons, which are formed under the influence of radiation (ultraviolet, X-ray and others) and (or) heating.

electrolytes - "liquid or solid substances and systems in which ions are present in any noticeable concentration, causing the passage of an electric current." Ions are formed in the process of electrolytic dissociation. When heated, the resistance of electrolytes decreases due to an increase in the number of molecules decomposed into ions. As a result of the passage of current through the electrolyte, the ions approach the electrodes and are neutralized, settling on them. Faraday's laws of electrolysis determine the mass of the substance released on the electrodes.

There is also an electric current of electrons in a vacuum, which is used in cathode ray devices.

Electric current is an ordered movement of charged particles. In solids, this is the movement of electrons (negatively charged particles) in liquid and gaseous bodies, this is the movement of ions (positively charged particles). Moreover, the current can be constant and variable, and they have a completely different movement of electric charges. In order to understand and master the topic of current flow in conductors, perhaps you first need to understand the basics of electrophysics in more detail. That's where I'll start.

So, how does electric current flow in general? We know that matter is made up of atoms. These are elementary particles of matter. The structure of the atom resembles our solar system, where the nucleus of the atom is located in the center. It consists of tightly pressed together protons (positive electrical particles) and neutrons (electrically neutral particles). Electrons (smaller particles with a negative charge) rotate around this nucleus with great speed in their orbits. Different substances have different numbers of electrons and orbits in which they rotate. Atoms of solids have a so-called crystal lattice. This is the structure of matter, in which atoms are arranged in a certain order relative to each other.

Where is the electric current coming from? It turns out that in some substances (current conductors) the electrons that are the most distant from their nucleus can break away from the atom and go to the neighboring atom. This movement of electrons is called free. It's just that electrons move inside matter from one atom to another. But if an external electromagnetic field is connected to this substance (electrical conductor), thereby creating an electrical circuit, then all free electrons will begin to move in one direction. This is precisely the movement of electric current inside the conductor.

Now let's look at what constitutes direct and alternating current. So, direct current always moves in only one direction. As mentioned at the very beginning, electrons move in solids, and ions move in liquid and gaseous bodies. Electrons are negatively charged particles. Consequently, in solids, electric current flows from the minus to the plus of the power source (electrons move along the electrical circuit). In liquids and gases, the current moves in two directions at once, or rather, simultaneously, electrons flow to the plus, and ions (separate atoms that are not interconnected by a crystal lattice, they are each on their own) flow to the minus of the power source.

Scientists, on the other hand, officially considered that the movement occurs from plus to minus (on the contrary, than it actually happens). So, from a scientific point of view, it is correct to say that the electric current moves from plus to minus, but from a real point of view (electrophysical nature) it is more correct to believe that the current flows from minus to plus (in solids). Perhaps this was done for some convenience.

Now, with regard to alternating electric current. Here everything is a little more complicated. If, in the case of direct current, the movement of charged particles has only one direction (physically, electrons with a minus sign flow towards the plus), then with alternating current, the direction of movement periodically changes to the opposite. You have probably heard that in an ordinary city power supply, an alternating voltage of 220 volts and a standard frequency of 50 hertz. So these 50 hertz indicate that the electric current in one second has time to go through a full cycle 50 times, which has a sinusoidal shape. In fact, in one second, the direction of the current changes as much as 100 times (it changes twice in one cycle).

P.S. The direction of current in electrical circuits is important. In many cases, if the circuit is designed for one direction of current, and you accidentally change it to the opposite one or connect an alternating current instead of direct current, then most likely the device will simply fail. Many semiconductors that work in circuits can break through and burn out when the current is reversed. So when connecting the power supply, the direction of the current must be strictly observed by you.

To the question what does it mean "current flows through the wires"? is he liquid? (sounds very childish, but I can’t ask in another way !!!) given by the author Lady the best answer is Well, it's a metaphor... In fact, electrons oscillate back and forth and orbit around an atom and transmit this oscillation to other electrons near another atom. At the same time, they do not move from their place. When they oscillate, they transfer charge to each other. Of course, this happens very quickly. At the speed of light (it is also the speed of propagation of electromagnetic radiation, one of the forms of which is electric current). Like this.

Answer from 22 answers[guru]

Hello! Here is a selection of topics with answers to your question: what does "current flows through wires" mean? is he liquid? (sounds very childish, but I can’t ask in another way !!!)

Answer from Correspondence student[guru]
movement of positively charged particles

Answer from Inca =) what's the difference[guru]
he doesn't run, he runs

Answer from firafine[guru]
ti molniyu kogda nibud videla?
nu vot, tok ne jidkii, eto volna, ti je radio slushaesh nu predstav

Answer from Oleg Salnikov[guru]
Electric current is the orderly movement of electrons in a conductor. From the negative pole to the positive.

Answer from Yotratiy Arkady[newbie]
the main thing - do not try to touch it

Answer from NoName NoSurname[expert]
Mdaaa ... do you think time is also liquid once the verb flows with it? So it happened in the Russian language (I won’t say for others right off the bat)! And as for the rest of the questions - I would be ashamed to ask this, they show that you are not far gone in terms of intelligence))

Answer from Makato[expert]
Current - the continuous movement of charged particles, smart people do not say that the current flows, the current - goes (the continuous movement of charged particles goes), there is no color, invisible, it does not sit in the outlet.
Sincerely. Giant of thought 🙂

Answer from Vladimir Petrov[guru]
it doesn’t sit in the outlet .. if you compare it with water, then in the outlet in one hole there is a mountain lake there are a lot of electrons, and in the other there is a lowland, and when you stick the electrons from the lake into its plug, they rush into the plain and do work on their way .. like boiling a kettle for you..

Answer from Arximed60[guru]
This is usually the way it is done in common parlance. In fact, by definition, electric current is the directed movement of charged particles. It has nothing to do with liquid.

Answer from mania mania[master]
Don't bother, you shouldn't know this because you're not an electrician.

Answer from // I/I X A I/I /\[guru]
Because the movement of electrons in a conductor is similar to the movement of water in a pipe.
Here is the phase - this is a pipe under pressure. Zero is the sewer. Voltage is water pressure. Current strength is the amount of water flowing per unit of time. Resistance is a narrow pipe. Earth - this is when water from a pipe pours onto the ground. And so on...

Answer from Andy[newbie]
In fact, current cannot go or flow. Current either exists or it doesn't. Current is, first of all, a flow. Does anyone say that the river flows??? The flow of a river is either there or it isn't. It is so? So. Then why does the overwhelming majority say "current is flowing" or "current is flowing"? Think, gentlemen!

Answer from Equilibrium[active]
Classical electronic theory:
Current - the ordered movement of electrons (in metals). Conditionally from plus to minus. The current is created by the potential difference at the two ends of the conductor (voltage).
Inexplicable but the fact:
From the point of view of classical theory, it is impossible to explain the following. Why, when rubbing amber or ebonite, they are charged, because they are dielectrics. When voltage is applied to the welding machines, the wires suitable for the electrodes begin to twitch.

Electric current can be represented as a directed movement of charged particles, which are traditionally taken as negative charge carriers or electrons. This statement is true for solid conductors, where the constant presence of free charged particles is considered the norm. For liquid and gaseous media, such carriers are positively charged ions, through which the transfer of matter is carried out.

physical entity

To clearly understand how current flows, you first need to be familiar with the basic physical phenomena that lead to the formation of an ordered flow. According to the molecular-atomistic theory, all natural bodies (regardless of their state of aggregation) consist of molecules and atoms, which include negatively charged electrons.

To clarify the principles of the formation of a stream of charged particles, it is most convenient to represent the composition of physical bodies as follows:

• The atoms that make up the molecules are conditionally represented as a nucleus located in the center and electrons rotating around it at the speed of light;
• Due to the different polarity of these two components, their combination under normal conditions has a zero charge;

Additional Information. In the atoms of any chemical element, the number of orbiting electrons is equal to the total charge of the nucleus, which ensures their electrical neutrality.

• In the atoms of some substances on the outer shells there are a large number of electrons, which, moreover, are removed from the nucleus at considerable distances by atomic standards;
• At some moments in time, some of them break away from their orbits and begin to freely "wander" between atoms, being attracted to neighboring nuclei or repelled from their electrons.

As a result of these processes, free charges appear in metal objects, which, when electrical potentials (voltages) of opposite sign are applied, begin to move in an orderly manner.

The directed movement of free charge carriers in solids (conductors) is called electric current.

In substances with a low content of free electrons, this movement is either completely impossible (dielectrics), or is limited to a small value. Such materials that are insufficiently saturated with electrical carriers are called semiconductors.

Types of currents

Electron flows present in conducting materials can move all the time in one direction or constantly change their direction. In the first case, they form alternating, and in the second - direct currents.

Variable flows are formed under the influence of voltages varying in magnitude and sign, applied to the ends of the conductor, and a potential difference of the same polarity is used to obtain a constant current signal.

Note! Changing currents flow through the electrical wiring of any apartment, and an example of the second variety is the unidirectional movement of electrons in batteries or batteries.

Historically, in a constant flow circuit, its direction is considered to be the movement from the "plus" of the power source to its "minus". Although, in reality, negative charge carriers move in the opposite direction (from "minus" to "plus"). But the previously accepted conditional direction was so fixed in the minds of people that it was left unchanged, considering the value of this parameter to be absolutely conditional.

In order to understand where alternating currents flow, one should start directly from their definition. In this situation, under the influence of an alternating potential (voltage), they change their direction with a certain periodicity.

Important! In Russian household networks, alternating voltage has a frequency of 50 Hertz. With appropriate periodicity, the current flowing through the wiring changes its direction.

In foreign electrical networks (in the USA and Japan, in particular), this frequency is 60 Hertz, which slightly increases efficiency with a simultaneous increase in losses in the supply lines.

Bidirectional movement of charges

In most metals, simultaneously with the flow of electrons, a reverse movement of particles opposite in sign, formed by positively charged atoms, is observed. Their movement coincides with the historically established definition (from “plus” to “minus”), so that, if desired, the movement of these constituents of matter can be taken as the true direction.

Let us add to the above that in liquids and gases, atomic particles with different charges (already mentioned ions and electrons) also move in opposite directions. This method of forming a flow of particles in a circuit is called electrolysis, which is widely used in various industries.

In conclusion, we note that, in contrast to the theoretical view, in practice, the conditionally chosen direction of electron movement in a particular electrical circuit is of fundamental importance. Any chain of radio elements included in it is initially calculated for a certain polarity of the applied voltage, and, consequently, for a given direction of the generated current signal.

Video

Charge in motion. It can take the form of a sudden discharge of static electricity, such as lightning. Or it could be a controlled process in generators, batteries, solar or fuel cells. Today we will consider the very concept of "electric current" and the conditions for the existence of an electric current.

Electric Energy

Most of the electricity we use comes in the form of alternating current from the electrical grid. It is created by generators that work according to Faraday's law of induction, due to which a changing magnetic field can induce an electric current in a conductor.

Generators have spinning coils of wire that pass through magnetic fields as they spin. As the coils rotate, they open and close with respect to the magnetic field and create an electrical current that changes direction with each turn. The current goes through a full cycle back and forth 60 times per second.

Generators can be powered by steam turbines heated by coal, natural gas, oil, or a nuclear reactor. From the generator, the current passes through a series of transformers, where its voltage increases. The diameter of the wires determines the amount and strength of current they can carry without overheating and wasting energy, and voltage is only limited by how well the lines are insulated from ground.

It is interesting to note that the current is carried by only one wire, not two. Its two sides are designated as positive and negative. However, since the polarity of alternating current changes 60 times per second, they have other names - hot (main power lines) and grounded (passing underground to complete the circuit).

Why is electricity needed?

There are many uses for electricity: it can light up your house, wash and dry your clothes, lift your garage door, boil water in a kettle, and power other household items that make our lives so much easier. However, the ability of the current to transmit information is becoming increasingly important.

When connected to the Internet, a computer uses only a small part of the electric current, but this is something without which a modern person cannot imagine his life.

The concept of electric current

Like a river current, a stream of water molecules, an electric current is a stream of charged particles. What is it that causes it, and why doesn't it always go in the same direction? When you hear the word flow, what do you think of? Perhaps it will be a river. It's a good association, because that's the reason the electric current got its name. It is very similar to the flow of water, only instead of water molecules moving along the channel, charged particles move along the conductor.

Among the conditions necessary for the existence of an electric current, there is an item that provides for the presence of electrons. Atoms in a conductive material have many of these free charged particles that float around and between the atoms. Their movement is random, so there is no flow in any given direction. What does it take for an electric current to exist?

The conditions for the existence of electric current include the presence of voltage. When it is applied to a conductor, all free electrons will move in the same direction, creating a current.

Curious about electric current

Interestingly, when electrical energy is transmitted through a conductor at the speed of light, the electrons themselves move much more slowly. In fact, if you walked leisurely next to a conductive wire, your speed would be 100 times faster than the electrons are moving. This is due to the fact that they do not need to travel huge distances to transfer energy to each other.

Direct and alternating current

Today, two different types of current are widely used - direct and alternating. In the first, the electrons move in one direction, from the "negative" side to the "positive" side. The alternating current pushes the electrons back and forth, changing the direction of the flow several times per second.

Generators used in power plants to produce electricity are designed to produce alternating current. You probably never noticed that the light in your house is actually flickering as the current direction changes, but it happens too fast for the eyes to recognize.

What are the conditions for the existence of direct electric current? Why do we need both types and which one is better? These are good questions. The fact that we still use both types of current suggests that they both serve specific purposes. As far back as the 19th century, it was clear that efficient transmission of power over long distances between a power plant and a house was possible only at very high voltages. But the problem was that sending really high voltage was extremely dangerous for people.

The solution to this problem was to reduce the stress outside the home before sending it inside. To this day, direct electric current is used for transmission over long distances, mainly because of its ability to easily convert to other voltages.

How electric current works

The conditions for the existence of an electric current include the presence of charged particles, a conductor, and voltage. Many scientists have studied electricity and found that there are two types of it: static and current.

It is the second that plays a huge role in the daily life of any person, as it is an electric current that passes through the circuit. We use it daily to power our homes and more.

What is electric current?

When electric charges circulate in a circuit from one place to another, an electric current is generated. The conditions for the existence of an electric current include, in addition to charged particles, the presence of a conductor. Most often it is a wire. Its circuit is a closed circuit in which current flows from a power source. When the circuit is open, he cannot complete the journey. For example, when the light in your room is off, the circuit is open, but when the circuit is closed, the light is on.

Current power

The conditions for the existence of an electric current in a conductor are greatly influenced by such a voltage characteristic as power. This is a measure of how much energy is being used over a given period of time.

There are many different units that can be used to express this characteristic. However, electrical power is almost measured in watts. One watt is equal to one joule per second.

Electric charge in motion

What are the conditions for the existence of an electric current? It can take the form of a sudden discharge of static electricity, such as lightning or a spark from friction with a woolen cloth. More often, however, when we talk about electric current, we mean a more controlled form of electricity that makes lights and appliances work. Most of the electrical charge is carried by the negative electrons and positive protons within the atom. However, the latter are mostly immobilized inside atomic nuclei, so the work of transferring charge from one place to another is done by electrons.

Electrons in a conductive material such as a metal are largely free to move from one atom to another along their conduction bands, which are the higher electron orbits. A sufficient electromotive force or voltage creates a charge imbalance that can cause electrons to move through a conductor in the form of an electric current.

If we draw an analogy with water, then take, for example, a pipe. When we open a valve at one end to let water enter the pipe, we don't have to wait for that water to work its way all the way to the end of the pipe. We get water at the other end almost instantly because the incoming water pushes the water that is already in the pipe. This is what happens in the case of an electric current in a wire.

Electric current: conditions for the existence of an electric current

Electric current is usually viewed as a flow of electrons. When the two ends of the battery are connected to each other with a metal wire, this charged mass passes through the wire from one end (electrode or pole) of the battery to the opposite. So, let's call the conditions for the existence of an electric current:

1. charged particles.
2. Conductor.
3. Voltage source.

However, not all so simple. What conditions are necessary for the existence of an electric current? This question can be answered in more detail by considering the following characteristics:

• Potential difference (voltage). This is one of the prerequisites. Between the 2 points there must be a potential difference, meaning that the repulsive force that is created by charged particles in one place must be greater than their force at another point. Voltage sources, as a rule, do not occur in nature, and electrons are distributed fairly evenly in the environment. Nevertheless, scientists managed to invent certain types of devices where these charged particles can accumulate, thereby creating the very necessary voltage (for example, in batteries).
• Electrical resistance (conductor). This is the second important condition that is necessary for the existence of an electric current. This is the path along which charged particles travel. Only those materials that allow electrons to move freely act as conductors. Those who do not have this ability are called insulators. For example, a metal wire will be an excellent conductor, while its rubber sheath will be an excellent insulator.

Having carefully studied the conditions for the emergence and existence of electric current, people were able to tame this powerful and dangerous element and direct it for the benefit of mankind.