What is electric current? The nature of electricity. Electric current: main characteristics and conditions for its existence

(electron-hole conductivity). Sometimes electric current is also called displacement current, resulting from a change in time of the electric field.

Electric current has the following manifestations:

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Classification

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

There are direct and alternating electric currents, as well as all kinds of alternating current. In such terms, the word "electric" is often omitted.

• DC Current - current, the direction and magnitude of which do not change with time.

Eddy currents

Eddy currents (Foucault currents) are “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 division of alternating current magnetic circuits into separate plates, isolated from each other and located perpendicular to the direction of eddy currents, is used, 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

It is historically accepted that current direction 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. .

Drift velocity of electrons

Radiation resistance is caused by the formation of electromagnetic waves around the conductor. This resistance is in complex dependence on the shape and dimensions of the conductor, on the wavelength of the emitted wave. For a single rectilinear conductor, in which everywhere the current is of the same direction and strength, and the length of which L is much less than the length of the electromagnetic wave emitted by it λ (\displaystyle \lambda ), the dependence of resistance on wavelength and conductor is relatively simple:

The most used electric current with a standard frequency of 50 Hz corresponds to a wave with a length of about 6 thousand kilometers, which is why the radiation power is usually negligibly small compared to the heat loss power. However, as the frequency of the current increases, the length of the emitted wave decreases, and the radiation power increases accordingly. A conductor capable of radiating appreciable energy is called an antenna.

Frequency

Frequency refers to an alternating current that periodically changes strength and/or direction. This also includes the most commonly used current, which varies according to a sinusoidal law.

An alternating current period is the shortest period of time (expressed in seconds) after which changes in current (and voltage) are repeated. The number of periods completed by the current per unit of time is called the frequency. Frequency is measured in hertz, one hertz (Hz) corresponds to one period per second.

Bias current

Sometimes, for convenience, the concept of displacement current is introduced. In Maxwell's equations, the displacement current is present on an equal footing with the current caused by the movement of charges. The intensity of the magnetic field depends on the total electric current, which is equal to the sum of the conduction current and the displacement current. By definition, the bias current density j D → (\displaystyle (\vec (j_(D))))- vector quantity proportional to the rate of change of the electric field E → (\displaystyle (\vec (E))) in time:

The fact is that with a change in the electric field, as well as with the flow of current, a magnetic field is generated, which makes these two processes similar to each other. In addition, a change in the electric field is usually accompanied by energy transfer. For example, when charging and discharging a capacitor, despite the fact that there is no movement of charged particles between its plates, they speak of a displacement current flowing through it, carrying some energy and closing the electrical circuit in a peculiar way. Bias current I D (\displaystyle I_(D)) in the capacitor is determined by the formula:

where Q (\displaystyle Q)- charge on the capacitor plates, U (\displaystyle U)- potential difference between the plates, C (\displaystyle C) is the capacitance of the capacitor.

Displacement current is not an electric current, because it is not related to the movement of an electric charge.

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 is an ionized gas. Electric charge is carried by ions (positive and negative) and free electrons, which are formed under the action 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 currents in nature

Electric current is used as a carrier of signals of varying complexity and types in different areas (telephone, radio, control panel, door lock button, and so on).

In some cases, unwanted electric currents appear, such as stray currents or short circuit current.

The use of electric current as a carrier of energy

• obtaining mechanical energy in various electric motors,
• obtaining thermal energy in heating devices, electric furnaces, during electric welding,
• obtaining light energy in lighting and signaling devices,
• excitation of electromagnetic oscillations of high frequency, ultrahigh frequency and radio waves,
• receiving sound,
• obtaining various substances by electrolysis, charging electric batteries. This is where electromagnetic energy is converted into chemical energy.
• creating a magnetic field (in electromagnets).

The use of electric current in medicine

• diagnostics - the biocurrents of healthy and diseased organs are different, while it is possible to determine the disease, its causes and prescribe treatment. The branch of physiology that studies electrical phenomena in the body is called electrophysiology.
  • Electroencephalography is a method for studying the functional state of the brain.
  • Electrocardiography is a technique for recording and studying electric fields during the work of the heart.
  • Electrogastrography is a method for studying the motor activity of the stomach.
  • Electromyography is a method for studying bioelectric potentials that occur in skeletal muscles.
• Treatment and resuscitation: electrical stimulation of certain areas of the brain; treatment of Parkinson's disease and epilepsy, also for electrophoresis. A pacemaker that stimulates the heart muscle with a pulsed current is used for bradycardia and other cardiac arrhythmias.

electrical safety

It includes legal, socio-economic, organizational and technical, sanitary and hygienic, medical and preventive, rehabilitation and other measures. Electrical safety rules are regulated by legal and technical documents, regulatory and technical framework. Knowledge of the basics of electrical safety is mandatory for personnel servicing electrical installations and electrical equipment. The human body is a conductor of electric current. Human resistance with dry and intact skin ranges from 3 to 100 kOhm.

The current passed through the human or animal body produces the following actions:

• thermal (burns, heating and damage to blood vessels);
• electrolytic (blood decomposition, violation of the physico-chemical composition);
• biological (irritation and excitation of body tissues, convulsions)
• mechanical (rupture of blood vessels under the action of steam pressure obtained by heating with blood flow)

The main factor determining the outcome of electric shock is the amount of current passing through the human body. According to safety engineering, electric current is classified as follows:

• safe a current is considered, the long passage of which through the human body does not harm him and does not cause any sensations, its value does not exceed 50 μA (alternating current 50 Hz) and 100 μA direct current;
• minimally perceptible human alternating current is about 0.6-1.5 mA (alternating current 50 Hz) and 5-7 mA direct current;
• threshold relentless called the minimum current of such a force at which a person is no longer able to tear his hands away from the current-carrying part by an effort of will. For alternating current, this is about 10-15 mA, for direct current - 50-80 mA;
• fibrillation threshold is called an alternating current (50 Hz) of about 100 mA and 300 mA of direct current, the effect of which is longer than 0.5 s with a high probability of causing fibrillation of the heart muscles. This threshold is simultaneously considered conditionally lethal for humans.

In Russia, in accordance with the Rules for the technical operation of electrical installations of consumers and the Rules for labor protection during the operation of electrical installations, 5 qualification groups for electrical safety have been established, depending on the qualifications and experience of the employee and the voltage of electrical installations.

What do we really know about electricity today? According to modern views, a lot, but if we delve into the essence of this issue in more detail, it turns out that humanity widely uses electricity without understanding the true nature of this important physical phenomenon.

The purpose of this article is not to refute the achieved scientific and technical applied research results in the field of electrical phenomena, which are widely used in the everyday life and industry of modern society. But humanity is constantly faced with a number of phenomena and paradoxes that do not fit into the framework of modern theoretical ideas regarding electrical phenomena - this indicates the lack of a complete understanding of the physics of this phenomenon.

Also, today science knows the facts when, it would seem, the studied substances and materials exhibit anomalous conductivity properties ( ) .

Such a phenomenon as the superconductivity of materials also does not have a completely satisfactory theory at present. There is only an assumption that superconductivity is quantum phenomenon , which is studied by quantum mechanics. A careful study of the basic equations of quantum mechanics: the Schrödinger equation, the von Neumann equation, the Lindblad equation, the Heisenberg equation and the Pauli equation, then their inconsistency becomes obvious. The fact is that the Schrödinger equation is not derived, but postulated by analogy with classical optics, based on the generalization of experimental data. The Pauli equation describes the motion of a charged particle with spin 1/2 (for example, an electron) in an external electromagnetic field, but the concept of spin is not related to the actual rotation of an elementary particle, and it is also postulated relative to the spin that there is a space of states that is in no way connected with the movement of an elementary particles in ordinary space.

In the book of Anastasia Novykh "Ezoosmos" there is a mention of the failure of quantum theory: "But the quantum mechanical theory of the structure of the atom, which considers the atom as a system of microparticles that do not obey the laws of classical mechanics, absolutely irrelevant . At first glance, the arguments of the German physicist Heisenberg and the Austrian physicist Schrödinger seem convincing to people, but if all this is considered from a different point of view, then their conclusions are only partially correct, and in general, both are completely wrong. The fact is that the first described the electron as a particle, and the other as a wave. By the way, the principle of wave-particle duality is also irrelevant, since it does not reveal the transition of a particle into a wave and vice versa. That is, some kind of scanty is obtained from the learned gentlemen. In fact, everything is very simple. In general, I want to say that the physics of the future is very simple and understandable. The main thing is to live until this future. As for the electron, it becomes a wave only in two cases. The first is when the external charge is lost, that is, when the electron does not interact with other material objects, say with the same atom. The second one is in the pre-osmic state, that is, when its internal potential decreases.

The same electrical impulses generated by the neurons of the human nervous system support the active complex and diverse functioning of the body. It is interesting to note that the action potential of a cell (a wave of excitation moving along the membrane of a living cell in the form of a short-term change in the membrane potential in a small area of ​​the excitable cell) is in a certain range (Fig. 1).

The lower limit of the action potential of a neuron is at -75 mV, which is very close to the value of the redox potential of human blood. If we analyze the maximum and minimum value of the action potential relative to zero, then it is very close to the percentage rounded meaning golden section , i.e. division of the interval in relation to 62% and 38%:

\(\Delta = 75mV+40mV = 115mV\)

115 mV / 100% = 75 mV / x 1 or 115 mV / 100% = 40 mV / x 2

x 1 = 65.2%, x 2 = 34.8%

All substances and materials known to modern science conduct electricity to one degree or another, since they contain electrons consisting of 13 phantom Po particles, which, in turn, are septon clumps (“PRIMORDIAL ALLATRA PHYSICS”, p. 61) . The question is only the voltage of the electric current, which is necessary to overcome the electrical resistance.

Since electrical phenomena are closely related to the electron, the PRIMORDIAL ALLATRA PHYSICS report provides the following information regarding this important elementary particle: “The electron is an integral part of the atom, one of the main structural elements of matter. Electrons form the electron shells of atoms of all currently known chemical elements. They are involved in almost all electrical phenomena that scientists are now aware of. But what electricity really is, official science still cannot explain, limited to general phrases, that it is, for example, "a set of phenomena due to the existence, movement and interaction of charged bodies or particles of electric charge carriers." It is known that electricity is not a continuous flow, but is transferred in portions - discretely».

According to modern ideas: electricity - this is a set of phenomena due to the existence, interaction and movement of electric charges. But what is electric charge?

Electric charge (amount of electricity) is a physical scalar quantity (a quantity, each value of which can be expressed by one real number), which determines the ability of bodies to be a source of electromagnetic fields and take part in electromagnetic interaction. Electric charges are divided into positive and negative (this choice is considered purely conditional in science and a well-defined sign is assigned to each of the charges). Bodies charged with a charge of the same sign repel, and oppositely charged bodies attract. When charged bodies move (both macroscopic bodies and microscopic charged particles that carry electric current in conductors), a magnetic field arises and phenomena take place that make it possible to establish the relationship of electricity and magnetism (electromagnetism).

Electrodynamics studies the electromagnetic field in the most general case (that is, time-dependent variable fields are considered) and its interaction with bodies that have an electric charge. Classical electrodynamics takes into account only the continuous properties of the electromagnetic field.

quantum electrodynamics studies electromagnetic fields that have discontinuous (discrete) properties, the carriers of which are field quanta - photons. The interaction of electromagnetic radiation with charged particles is considered in quantum electrodynamics as the absorption and emission of photons by particles.

It is worth considering why a magnetic field appears around a conductor with current, or around an atom, along whose orbits electrons move? The fact is that " what today is called electricity is actually a special state of the septon field , in the processes of which the electron in most cases takes part on an equal basis with its other additional "components" ” (“PRIMARY ALLATRA PHYSICS”, p. 90) .

And the toroidal shape of the magnetic field is due to the nature of its origin. As the article says: “Given the fractal patterns in the Universe, as well as the fact that the septon field in the material world within 6 dimensions is the fundamental, unified field on which all interactions known to modern science are based, it can be argued that they all also have the form Torah. And this statement may be of particular scientific interest to modern researchers.. Therefore, the electromagnetic field will always take the form of a torus, like a septon torus.

Consider a spiral through which an electric current flows and how exactly its electromagnetic field is formed ( https://www.youtube.com/watch?v=0BgV-ST478M).

Rice. 2. Field lines of a rectangular magnet

Rice. 3. Field lines of a spiral with current

Rice. 4. Lines of force of individual sections of the spiral

Rice. 5. Analogy between the lines of force of a spiral and atoms with orbital electrons

Rice. 6. A separate fragment of a spiral and an atom with lines of force

CONCLUSION: mankind has yet to learn the secrets of the mysterious phenomenon of electricity.

Petr Totov

Keywords: PRIMORDIAL ALLATRA PHYSICS, electric current, electricity, nature of electricity, electric charge, electromagnetic field, quantum mechanics, electron.

Literature:

New. A., Ezoosmos, K.: LOTOS, 2013. - 312 p. http://schambala.com.ua/book/ezoosmos

Report "PRIMORDIAL ALLATRA PHYSICS" of the international group of scientists of the ALLATRA International Public Movement, ed. Anastasia Novykh, 2015;

Directed (ordered) movement of particles, electric charge carriers, in an electromagnetic field.

What is electric current in different substances? Let us take, respectively, the moving particles:

• in metals - electrons,
• in electrolytes - ions (cations and anions),
• in gases - ions and electrons,
• in vacuum under certain conditions - electrons,
• in semiconductors - 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 manifests itself as follows:

• heats conductors (the phenomenon is not observed in superconductors);
• changes the chemical composition of the conductor (this phenomenon is primarily characteristic of electrolytes);
• creates a magnetic field (manifested in all conductors without exception).

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 ""convection"".

Currents are divided into direct and alternating. There are also various types of alternating current. When defining the types of current, the word "electric" is omitted.

• D.C- current, the direction and magnitude of which do not change with time. Can be pulsating, such as a rectified variable that is unidirectional.
• Alternating current is an electric current that changes with time. Alternating current is any current that is not direct.
• Periodic current- electric current, the instantaneous values ​​of which are repeated at regular intervals in an unchanged sequence.
• Sinusoidal current- periodic electric current, which is a sinusoidal function of time. Among the alternating currents, the main one is the current, the value of which varies according to a sinusoidal law. Any periodic non-sinusoidal current can be represented as a combination of sinusoidal harmonic components (harmonics) with corresponding amplitudes, frequencies and initial phases. In this case, the electrostatic 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. 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 current- alternating current, (starting from a frequency of approximately tens of kHz), for which such phenomena become significant, which are either useful, determining its use, or harmful, against which the necessary measures are taken, such as electromagnetic wave radiation and the skin effect. In addition, if the wavelength of the alternating current radiation becomes comparable with the dimensions of the elements of the electrical circuit, then the condition of quasi-stationarity is violated, which requires special approaches to the calculation and design of such circuits.
• Ripple current is a periodic electric current, the average value of which over the period is different from zero.
• Unidirectional current is an electric current that does not change its direction.

Eddy currents

Eddy currents (or Foucault currents) are closed electric currents in a massive conductor that occur 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 division of alternating current magnetic circuits into separate plates, isolated from each other and located perpendicular to the direction of eddy currents, is used, 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

It is historically 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.

Drift velocity of electrons

The drift velocity of the directed motion of particles in conductors caused by an external field 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.

Strength and current density

Electric current has quantitative characteristics: scalar - current strength, and vector - current density.

Strength current a is a physical quantity equal to the ratio of the amount of charge

Gone for some time

through the cross section of the conductor, to the value of this time interval.

Current strength in SI is measured in amperes (international and Russian designation: A).

According to Ohm's law, the current

in the circuit section is directly proportional to the electrical voltage

Applied to this section of the circuit, and is inversely proportional to its resistance

If the electric current is not constant in the circuit section, then the voltage and current strength are constantly changing, while for ordinary alternating current the average values ​​​​of voltage and current strength are equal to zero. However, the average power of the heat released in this case is not equal to zero.

Therefore, the following terms are used:

• instantaneous voltage and current, that is, acting at a given moment in time.
• peak voltage and current, that is, the maximum absolute values
• effective (effective) voltage and current strength are determined by the thermal effect of the current, that is, they have the same values ​​\u200b\u200bthat they have for direct current with the same thermal effect.

current density- a vector, the absolute value of which is equal to the ratio of the strength of the current flowing through a certain section of the conductor, perpendicular to the direction of the current, to the area of ​​this section, and the direction of the vector coincides with the direction of movement of the positive charges that form the current.

According to Ohm's law in differential form, the current density in the medium

proportional to the electric field strength

and conductivity of the medium

Power

In the presence of current in the conductor, work is done against the forces of resistance. The electrical resistance of any conductor consists of two components:

• active resistance - resistance to heat generation;
• reactance - resistance due to the transfer of energy to an electric or magnetic field (and vice versa).

Generally, most of the work done by an electric current is released as heat. The power of heat loss is a value equal to the amount of heat released per unit time. According to the Joule-Lenz law, the power of heat loss in a conductor is proportional to the strength of the flowing current and the applied voltage:

Power is measured in watts.

In a continuous medium, the volumetric power loss

is determined by the scalar product of the current density vector

and electric field strength vector

at this point:

Volumetric power is measured in watts per cubic meter.

Radiation resistance is caused by the formation of electromagnetic waves around the conductor. This resistance is in complex dependence on the shape and dimensions of the conductor, on the wavelength of the emitted wave. For a single rectilinear conductor, in which everywhere the current is of the same direction and strength, and the length of which L is much less than the length of the electromagnetic wave emitted by it

The dependence of resistance on wavelength and conductor is relatively simple:

The most used electric current with a standard frequency of 50 "Hz" corresponds to a wave length of about 6 thousand kilometers, which is why the radiation power is usually negligibly small compared to the heat loss power. However, as the frequency of the current increases, the length of the emitted wave decreases, and the radiation power increases accordingly. A conductor capable of radiating appreciable energy is called an antenna.

Frequency

Frequency refers to an alternating current that periodically changes strength and/or direction. This also includes the most commonly used current, which varies according to a sinusoidal law.

An alternating current period is the shortest period of time (expressed in seconds) after which changes in current (and voltage) are repeated. The number of periods completed by the current per unit of time is called the frequency. Frequency is measured in hertz, one hertz (Hz) corresponds to one period per second.

Bias current

Sometimes, for convenience, the concept of displacement current is introduced. In Maxwell's equations, the displacement current is present on an equal footing with the current caused by the movement of charges. The intensity of the magnetic field depends on the total electric current, which is equal to the sum of the conduction current and the displacement current. By definition, the bias current density

Vector quantity proportional to the rate of change of the electric field

in time:

The fact is that when the electric field changes, as well as when the current flows, a magnetic field is generated, which makes these two processes similar to each other. In addition, a change in the electric field is usually accompanied by energy transfer. For example, when charging and discharging a capacitor, despite the fact that there is no movement of charged particles between its plates, they speak of a displacement current flowing through it, carrying some energy and closing the electrical circuit in a peculiar way. Bias current

in the capacitor is determined by the formula:

The charge on the capacitor plates,

Electrical voltage in between the plates,

The electrical capacitance of a capacitor.

Displacement current is not an electric current, because it is not related to the movement of an electric charge.

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

Electrolytes are 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 currents in nature

Atmospheric electricity is electricity that is contained in the air. For the first time, Benjamin Franklin showed the presence of electricity in the air and explained the cause of thunder and lightning.

Subsequently, it was established that electricity accumulates in the condensation of vapors in the upper atmosphere, and the following laws were indicated, which atmospheric electricity follows:

• with a clear sky, as well as with a cloudy sky, the electricity of the atmosphere is always positive, if at some distance from the observation point it does not rain, hail or snow;
• the voltage of the electricity of the clouds becomes strong enough to release it from the environment only when the cloud vapors condense into raindrops, as evidenced by the fact that there are no lightning discharges without rain, snow or hail at the place of observation, excluding the return stroke of lightning;
• atmospheric electricity increases with increasing humidity and reaches a maximum when rain, hail and snow fall;
• the place where it rains is a reservoir of positive electricity, surrounded by a belt of negative electricity, which, in turn, is enclosed in a belt of positive. At the boundaries of these belts, the stress is zero.

The movement of ions under the action of electric field forces forms a vertical conduction current in the atmosphere with an average density equal to about (2÷3)·10 −12 A/m².

The total current flowing to the entire surface of the Earth is approximately 1800 A.

Lightning is a natural sparking electrical discharge. The electrical nature of the auroras was established. St. Elmo's fires are a natural corona electrical discharge.

Biocurrents - the movement of ions and electrons plays a very significant role in all life processes. The biopotential created in this case exists both at the intracellular level and in individual parts of the body and organs. The transmission of nerve impulses occurs with the help of electrochemical signals. Some animals (electric rays, electric eel) are able to accumulate a potential of several hundred volts and use this for self-defense.

Application

When studying the electric current, many of its properties were discovered, which allowed it to find practical applications in various fields of human activity, and even create new areas that would not be possible without the existence of an electric current. After the electric current found practical application, and for the reason that the electric current can be obtained in various ways, a new concept arose in the industrial sphere - the electric power industry.

Electric current is used as a carrier of signals of varying complexity and types in different areas (telephone, radio, control panel, door lock button, and so on).

In some cases, unwanted electric currents appear, such as stray currents or short circuit current.

The use of electric current as a carrier of energy

• obtaining mechanical energy in various electric motors,
• obtaining thermal energy in heating devices, electric furnaces, during electric welding,
• obtaining light energy in lighting and signaling devices,
• excitation of electromagnetic oscillations of high frequency, ultrahigh frequency and radio waves,
• receiving sound,
• obtaining various substances by electrolysis, charging electric batteries. This is where electromagnetic energy is converted into chemical energy.
• creating a magnetic field (in electromagnets).

The use of electric current in medicine

• diagnostics - the biocurrents of healthy and diseased organs are different, while it is possible to determine the disease, its causes and prescribe treatment. The branch of physiology that studies electrical phenomena in the body is called electrophysiology.
  • Electroencephalography is a method for studying the functional state of the brain.
  • Electrocardiography is a technique for recording and studying electric fields during the work of the heart.
  • Electrogastrography is a method for studying the motor activity of the stomach.
  • Electromyography is a method for studying bioelectric potentials that occur in skeletal muscles.
• Treatment and resuscitation: electrical stimulation of certain areas of the brain; treatment of Parkinson's disease and epilepsy, also for electrophoresis. A pacemaker that stimulates the heart muscle with a pulsed current is used for bradycardia and other cardiac arrhythmias.

electrical safety

It includes legal, socio-economic, organizational and technical, sanitary and hygienic, medical and preventive, rehabilitation and other measures. Electrical safety rules are regulated by legal and technical documents, regulatory and technical framework. Knowledge of the basics of electrical safety is mandatory for personnel servicing electrical installations and electrical equipment. The human body is a conductor of electric current. Human resistance with dry and intact skin ranges from 3 to 100 kOhm.

The current passed through the human or animal body produces the following actions:

• thermal (burns, heating and damage to blood vessels);
• electrolytic (blood decomposition, violation of the physico-chemical composition);
• biological (irritation and excitation of body tissues, convulsions)
• mechanical (rupture of blood vessels under the action of steam pressure obtained by heating with blood flow)

The main factor determining the outcome of electric shock is the amount of current passing through the human body. According to safety measures, electric current is classified as follows:

• ""safe"" is the current, the long passage of which through the human body does not harm him and does not cause any sensations, its value does not exceed 50 μA (alternating current 50 Hz) and 100 μA direct current;
• The "minimum perceptible"" alternating current is about 0.6-1.5 mA (alternating current 50 Hz) and 5-7 mA direct current;
• threshold "non-letting" is the minimum current of such a force at which a person is no longer able to tear his hands away from the current-carrying part by an effort of will. For alternating current, this is about 10-15 mA, for direct current - 50-80 mA;
• "Fibrillation Threshold" refers to an AC current (50 Hz) of about 100 mA and 300 mA DC that is more than 0.5 s likely to cause cardiac muscle fibrillation. This threshold is simultaneously considered conditionally lethal for humans.

In Russia, in accordance with the Rules for the technical operation of electrical installations of consumers (Order of the Ministry of Energy of the Russian Federation dated January 13, 2003 No. 6 “On approval of the Rules for the technical operation of electrical installations of consumers”) and the Rules for labor protection during the operation of electrical installations (Order of the Ministry of Energy of the Russian Federation of December 27, 2000 N 163 “On approval of the Intersectoral Rules for Labor Protection (Safety Rules) for the Operation of Electrical Installations”), 5 qualification groups for electrical safety have been established depending on the qualifications and length of service of the employee and the voltage of electrical installations.

Notes

• Baumgart K. K., Electric current.
• A.S. Kasatkin. Electrical engineering.
• SOUTH. Sindeev. Electrical engineering with electronic elements.

What is called current strength? This question arose more than once or twice in the process of discussing various issues. Therefore, we decided to deal with it in more detail, and we will try to make it as accessible as possible without a huge number of formulas and incomprehensible terms.

So what is called electric current? This is a directed stream of charged particles. But what are these particles, why are they suddenly moving, and where? This is not very clear. So let's look at this issue in more detail.

• Let's start with the question about charged particles, which, in fact, are carriers of electric current. They are different in different substances. For example, what is an electric current in metals? These are electrons. In gases, electrons and ions; in semiconductors - holes; and in electrolytes, these are cations and anions.

• These particles have a certain charge. It can be positive or negative. The definition of positive and negative charge is given conditionally. Particles with the same charge repel each other, while particles with opposite charges attract.

• Based on this, it turns out logical that the movement will occur from the positive pole to the negative. And the more charged particles there are on one charged pole, the more of them will move to the pole with a different sign.
• But this is all deep theory, so let's take a concrete example. Let's say we have an outlet to which no devices are connected. Is there a current there?
• To answer this question, we need to know what voltage and current are. To make it clearer, let's look at this using the example of a pipe with water. To put it simply, the pipe is our wire. The cross section of this pipe is the voltage of the electrical network, and the flow rate is our electric current.
• We return to our outlet. If we draw an analogy with a pipe, then an outlet without electrical appliances connected to it is a pipe closed by a valve. That is, there is no electricity.

• But there is tension there. And if in the pipe, in order for the flow to appear, it is necessary to open the valve, then in order to create an electric current in the conductor, it is necessary to connect the load. This can be done by plugging the plug into an outlet.
• Of course, this is a very simplified presentation of the question, and some professionals will find fault with me and point out inaccuracies. But it gives an idea of ​​what is called electric current.

Direct and alternating current

The next question that we propose to understand is: what is alternating current and direct current. After all, many do not quite correctly understand these concepts.

A constant current is a current that does not change its magnitude and direction over time. Quite often, a pulsating current is also referred to as a constant, but let's talk about everything in order.

• Direct current is characterized by the fact that the same number of electric charges constantly replace each other in the same direction. The direction is from one pole to the other.
• It turns out that the conductor always has either a positive or a negative charge. And over time it is unchanged.

Note! When determining the direction of DC current, there may be inconsistencies. If the current is formed by the movement of positively charged particles, then its direction corresponds to the movement of particles. If the current is formed by the movement of negatively charged particles, then its direction is considered to be opposite to the movement of particles.

• But under the concept of what direct current is often referred to as the so-called pulsating current. It differs from constant only in that its value changes over time, but at the same time it does not change its sign.
• Let's say we have a current of 5A. For direct current, this value will be unchanged throughout the entire period of time. For a pulsating current, in one period of time it will be 5, in another 4, and in the third 4.5. But at the same time, it in no case decreases below zero, and does not change its sign.

• This ripple current is very common when converting AC to DC. It is this pulsating current that your inverter or diode bridge in electronics produces.
• One of the main advantages of direct current is that it can be stored. You can do this with your own hands, using batteries or capacitors.

Alternating current

To understand what an alternating current is, we need to imagine a sinusoid. It is this flat curve that best characterizes the change in direct current, and is the standard.

Note! You can clearly see what alternating and direct current are, using the example of an ordinary light bulb. This is especially evident on low-quality diode lamps, but if you look closely, you can also see it on an ordinary incandescent lamp. When operating on direct current, they burn with a steady light, and when operating on alternating current, they flicker slightly.

What is power and current density?

Well, we found out what is direct current and what is alternating current. But you probably still have a lot of questions. We will try to consider them in this section of our article.

From this video you can learn more about what power is.

• And the first of these questions will be: what is the voltage of an electric current? Voltage is the potential difference between two points.

• The question immediately arises, what is the potential? Now professionals will again find fault with me, but let's put it this way: this is an excess of charged particles. That is, there is one point at which there is an excess of charged particles - and there is a second point where these charged particles are either more or less. This difference is called voltage. It is measured in volts (V).

• Let's take an ordinary socket as an example. All of you probably know that its voltage is 220V. We have two wires in the socket, and a voltage of 220V means that the potential of one wire is greater than the potential of the second wire just for these 220V.
• We need an understanding of the concept of voltage in order to understand what the power of an electric current is. Although from a professional point of view, this statement is not entirely true. Electric current does not have power, but is its derivative.

• To understand this point, let's go back to our water pipe analogy. As you remember, the cross section of this pipe is the voltage, and the flow rate in the pipe is the current. So: power is the amount of water that flows through this pipe.
• It is logical to assume that with equal cross sections, that is, voltages, the stronger the flow, that is, the electric current, the greater the flow of water to move through the pipe. Accordingly, the more power will be transferred to the consumer.
• But if, in analogy with water, we can transfer a strictly defined amount of water through a pipe of a certain section, since water does not compress, then everything is not so with electric current. Through any conductor, we can theoretically transmit any current. But in practice, a conductor of a small cross section at a high current density will simply burn out.

• In this regard, we need to understand what current density is. Roughly speaking, this is the number of electrons that move through a certain section of the conductor per unit time.
• This number should be optimal. After all, if we take a conductor of large cross section, and we transmit a small current through it, then the price of such an electrical installation will be high. At the same time, if we take a conductor of a small cross section, then due to the high current density it will overheat and quickly burn out.
• In this regard, the PUE has a corresponding section that allows you to select conductors based on the economic current density.

• But back to the concept of what is current power? As we understood by our analogy, with the same pipe section, the transmitted power depends only on the current strength. But if the cross section of our pipe is increased, that is, the voltage is increased, in this case, at the same values ​​of the flow velocity, completely different volumes of water will be transmitted. The same is true in electrical.

• The higher the voltage, the less current is needed to transfer the same power. That is why high-voltage power lines are used to transmit high power over long distances.

After all, a line with a wire cross section of 120 mm 2 for a voltage of 330 kV is capable of transmitting many times more power in comparison with a line of the same cross section, but with a voltage of 35 kV. Although what is called the current strength, they will be the same.

Methods for transmitting electric current

What is current and voltage we figured out. It's time to figure out how to distribute electric current. This will allow you to feel more confident in dealing with electrical appliances in the future.

As we have already said, the current can be variable and constant. In industry, and in your sockets, alternating current is used. It is more common as it is easier to wire. The fact is that it is quite difficult and expensive to change the DC voltage, and you can change the AC voltage using ordinary transformers.

Note! No AC transformer will run on DC. Since the properties that it uses are inherent only in alternating current.

• But this does not mean at all that direct current is not used anywhere. It has another useful property that is not inherent in a variable. It can be accumulated and stored.
• In this regard, direct current is used in all portable electrical appliances, in railway transport, as well as in some industrial facilities where it is necessary to maintain operability even after a complete power outage.

• Batteries are the most common way to store electrical energy. They have special chemical properties that allow them to accumulate and then, if necessary, give off direct current.
• Each battery has a strictly limited amount of stored energy. It is called the capacity of the battery, and partly it is determined by the starting current of the battery.
• What is the starting current of a battery? This is the amount of energy that the battery is able to give at the very initial moment of connecting the load. The fact is that, depending on the physical and chemical properties, batteries differ in the way they release the accumulated energy.

• Some can give immediately and a lot. Because of this, they, of course, are quickly discharged. And the second give a long time, but a little bit. In addition, an important aspect of the battery is the ability to maintain voltage.
• The fact is that, as the instructions say, for some batteries, as the capacity returns, their voltage also gradually decreases. And other batteries are able to give almost the entire capacity with the same voltage. Based on these basic properties, these storage facilities are selected for electricity.
• For direct current transmission, in all cases, two wires are used. This is a positive and negative wire. Red and blue.

Alternating current

But with alternating current, everything is much more complicated. It can be transmitted over one, two, three or four wires. To explain this, we need to deal with the question: what is a three-phase current?

• Alternating current is generated by a generator. Usually almost all of them have a three-phase structure. This means that the generator has three outputs, and each of these outputs produces an electric current that differs from the previous ones by an angle of 120⁰.

• In order to understand this, let's remember our sinusoid, which is a model for describing alternating current, and according to the laws of which it changes. Let's take three phases - "A", "B" and "C", and take a certain point in time. At this point, phase "A" sine wave is at zero point, phase "B" sine wave is at extreme positive point, and phase "C" sine wave is at extreme negative point.
• Each subsequent unit of time, the alternating current in these phases will change, but synchronously. That is, after a certain time, in phase "A" there will be a negative maximum. In phase "B" there will be zero, and in phase "C" - a positive maximum. And after a while, they will change again.

• As a result, it turns out that each of these phases has its own potential, which is different from the potential of the neighboring phase. Therefore, there must be something between them that does not conduct electricity.
• This potential difference between two phases is called line voltage. In addition, they have a potential difference relative to the ground - this voltage is called phase.
• And so, if the line voltage between these phases is 380V, then the phase voltage is 220V. It differs by a value in √3. This rule is always valid for any voltage.

• Based on this, if we need a voltage of 220V, then we can take one phase wire, and a wire that is rigidly connected to the ground. And we get a single-phase 220V network. If we need a 380V network, then we can only take any 2 phases and connect some kind of heating device as in the video.

But in most cases, all three phases are used. All powerful consumers are connected to a three-phase network.

Conclusion

What is induction current, capacitive current, starting current, no-load current, negative sequence currents, stray currents and much more, we simply cannot consider in one article.

After all, the issue of electric current is quite voluminous, and an entire science of electrical engineering has been created to consider it. But we really hope that we were able to explain in an accessible language the main aspects of this issue, and now the electric current will not be something terrible and incomprehensible for you.

At today's meeting, we will talk about electricity, which has become an integral part of modern civilization. The power industry has invaded every area of ​​our lives. And the presence in every home of household appliances that use electric current is so natural and integral part of life that we take it for granted.

So, the attention of our readers is offered basic information about the electric current.

What is electric current

By electric current is meant directed motion of charged particles. Substances containing a sufficient amount of free charges are called conductors. And the totality of all devices interconnected by means of wires is called an electrical circuit.

In everyday life we use electricity passing through metal conductors. The charge carriers in them are free electrons.

Usually they rush randomly between atoms, but the electric field forces them to move in a certain direction.

How does this happen

The flow of electrons in a circuit can be compared to the flow of water falling from a high level to a low level. The role of the level in electrical circuits is played by the potential.

For the current to flow in the circuit, a constant potential difference must be maintained at its ends, i.e. voltage.

It is usually denoted by the letter U and measured in volts (B).

Due to the applied voltage, an electric field is established in the circuit, which gives the electrons a directed movement. The higher the voltage, the stronger the electric field, and hence the intensity of the flow of directionally moving electrons.

The speed of propagation of the electric current is equal to the speed at which the electric field is established in the circuit, i.e., 300,000 km/s, but the speed of the electrons barely reaches only a few mm per second.

It is generally accepted that the current flows from a point with a large potential, i.e. from (+) to a point with a lower potential, i.e. to (-). The voltage in the circuit is maintained by a current source, such as a battery. The sign (+) at its end means a lack of electrons, the sign (-) their excess, since electrons are carriers of precisely a negative charge. As soon as the circuit with the current source becomes closed, the electrons rush from the place where they are in excess to the positive pole of the current source. Their path runs through wires, consumers, measuring instruments and other circuit elements.

Note that the direction of the current is opposite to the direction of the electrons.

Just the direction of the current, by agreement of scientists, was determined before the nature of the current in metals was established.

Some quantities characterizing the electric current

Current strength. The electric charge passing through the cross section of the conductor in 1 second is called the current strength. For its designation, the letter I is used, measured in amperes (A).

Resistance. The next value to be aware of is resistance. It arises due to collisions of directionally moving electrons with ions of the crystal lattice. As a result of such collisions, electrons transfer part of their kinetic energy to ions. As a result, the conductor heats up, and the current decreases. Resistance is denoted by the letter R and is measured in ohms (Ohm).

The resistance of a metal conductor is the greater, the longer the conductor and the smaller its cross-sectional area. With the same length and diameter of the wire, conductors made of silver, copper, gold and aluminum have the least resistance. For obvious reasons, aluminum and copper wires are used in practice.

Power. When performing calculations for electrical circuits, it is sometimes necessary to determine the power consumption (P).

To do this, the current flowing through the circuit should be multiplied by the voltage.

The unit of measure for power is the watt (W).

Direct and alternating current

The current given by a variety of batteries and accumulators is constant. This means that the current strength in such a circuit can only be changed in magnitude by changing its resistance in various ways, while its direction remains unchanged.

But most household appliances consume alternating current, i.e., the current, the magnitude and direction of which is continuously changing according to a certain law.

It is produced in power plants and then transported through high-voltage transmission lines to our homes and businesses.

In most countries, the frequency of current reversal is 50 Hz, i.e. occurs 50 times per second. In this case, each time the current strength gradually increases, reaches a maximum, then decreases to 0. Then this process is repeated, but with the opposite direction of the current.

In the US, all appliances operate at 60 Hz. An interesting situation has developed in Japan. There, one third of the country uses alternating current with a frequency of 60 Hz, and the rest - 50 Hz.

Caution - electricity

Electric shocks can be caused by using electrical appliances and from lightning strikes because The human body is a good conductor of electricity. Often, electrical injuries are received by stepping on a wire lying on the ground or pushing away dangling electrical wires with your hands.

Voltage over 36 V is considered dangerous for humans. If a current of only 0.05 A passes through the human body, it can cause involuntary muscle contraction, which will not allow the person to independently break away from the source of damage. A current of 0.1 A is lethal.

Alternating current is even more dangerous, because it has a stronger effect on a person. This friend and helper of ours in a number of cases turns into a merciless enemy, causing a violation of breathing and heart function, up to its complete stop. It leaves terrible marks on the body in the form of severe burns.

How to help the victim? First of all, turn off the source of damage. And then take care of first aid.

Our acquaintance with electricity is coming to an end. Let's add just a few words about marine life with "electric weapons". These are some types of fish, sea eel and stingray. The most dangerous of them is sea eel.

Do not swim to him at a distance of less than 3 meters. His blow is not fatal, but consciousness can be lost.

If this message was useful to you, I would be glad to see you