Where does the electrostatic field occur? Definition of electrostatic field. Application in chemistry

An electric field is a vector field acting around particles with an electric charge. It is part of the electromagnetic field. It is characterized by a lack of real visualization. It is invisible, and can only be noticed as a result of force, to which other charged bodies with opposite poles react.

How the electric field works and works

In essence, a field is a special state of matter. Its action is manifested in the acceleration of bodies or particles with an electric charge. Its characteristic features include:

• Action only when electrically charged.
• No boundaries.
• The presence of a certain magnitude of impact.
• Possibility of determination only by the result of an action.

The field is inextricably linked with the charges that are in a certain particle or body. It can form in two cases. The first involves its appearance around electric charges, and the second when electromagnetic waves move, when the electromagnetic field changes.

Electric fields act on electrically charged particles that are stationary relative to the observer. As a result, they gain power. An example of the influence of the field can be observed in everyday life. To do this, it is enough to create an electric charge. Physics textbooks offer the simplest example for this, when a dielectric is rubbed against a woolen product. It is quite possible to get a field by taking a plastic ballpoint pen and rubbing it on your hair. A charge is formed on its surface, which leads to the appearance of an electric field. As a result, the handle attracts small particles. If you present it to finely torn pieces of paper, they will be attracted to it. The same result can be achieved when using a plastic comb.

A common everyday example of the manifestation of an electric field is the formation of small flashes of light when removing clothing made from synthetic materials. As a result of being on the body, dielectric fibers accumulate charges around themselves. When such an item of clothing is removed, the electric field is exposed to various forces, which leads to the formation of light flashes. This is especially true for winter clothing, in particular sweaters and scarves.

Field properties

To characterize the electric field, 3 indicators are used:

• Potential.
• Tension.
• Voltage.

Potential

This property is one of the main ones. Potential indicates the amount of stored energy used to move charges. As they shift, the energy is wasted, gradually approaching zero. A clear analogy of this principle can be an ordinary steel spring. In a calm position, it does not have any potential, but only until the moment it is compressed. From such an influence it receives energy of counteraction, therefore, after the influence ceases, it will definitely accelerate. When the spring is released, it immediately straightens. If objects get in her way, she will start moving them. Returning directly to the electric field, the potential can be compared with the applied efforts to straighten back.

An electric field has potential energy, which makes it capable of performing a certain effect. But by moving the charge in space, it depletes its resource. In the same case, if the movement of a charge within the field is carried out under the influence of an external force, then the field not only does not lose its potential, but also replenishes it.

Also, for a better understanding of this value, one more example can be given. Let us assume that an insignificant positively charged charge is located far beyond the action of the electric field. This makes it completely neutral and eliminates mutual contact. If, as a result of the influence of any external force, the charge moves towards the electric field, then, upon reaching its boundary, it will be drawn into a new trajectory. The field energy expended on the influence relative to the charge at a certain point of influence will be called the potential at this point.

The expression of electric potential is carried out through the unit of measurement Volt.

Tension

This indicator is used to quantify the field. This value is calculated as the ratio of the positive charge affecting the force of action. In simple terms, tension expresses the strength of an electric field in a certain place and time. The higher the tension, the more pronounced the influence of the field on surrounding objects or living beings will be.

Voltage

This parameter is formed from the potential. It is used to demonstrate the quantitative relationship of the action that a field produces. That is, the potential itself shows the amount of accumulated energy, and the voltage shows the losses to ensure the movement of charges.

In an electric field, positive charges move from points with high potential to places where it is lower. As for negative charges, they move in the opposite direction. As a result, work is carried out using the potential energy of the field. In fact, the voltage between points qualitatively expresses the work done by the field to transfer a unit of oppositely charged charges. Thus, the terms voltage and potential difference are one and the same.

Visual manifestation of the field

The electric field has a conventional visual expression. Graphic lines are used for this. They coincide with the lines of force that radiate charges around them. In addition to the line of action of forces, their direction is also important. To classify lines, it is customary to use a positive charge as a basis for determining directions. Thus, the arrow of the field movement goes from positive particles to negative ones.

Drawings depicting electric fields have an arrow-shaped direction on the lines. Schematically, they always have a conventional beginning and end. This way they don't turn on themselves. The lines of force originate at the location of the positive charge and end at the location of the negative particles.

An electric field can have different types of lines depending not only on the polarity of the charge that contributes to their formation, but also on the presence of external factors. So, when opposite fields meet, they begin to act attractively on each other. Distorted lines take on the shape of bent arcs. In the same case, when 2 identical fields meet, they are repelled in opposite directions.

Scope of application

The electric field has a number of properties that have found useful applications. This phenomenon is used to create various equipment for work in several very important areas.

Use in medicine

The effect of an electric field on certain areas of the human body allows one to increase its actual temperature. This property has found its application in medicine. Specialized devices provide effects on the necessary areas of damaged or diseased tissue. As a result, their blood circulation improves and a healing effect occurs. The field acts with a high frequency, so a point effect on temperature produces results and is quite noticeable for the patient.

Application in chemistry

This field of science involves the use of various pure or mixed materials. In this regard, work with electronic fields could not bypass this industry. The components of mixtures interact with the electric field in different ways. In chemistry, this property is used to separate liquids. This method has found laboratory application, but is also found in industry, although less frequently. For example, when exposed to a field, polluting components in oil are separated.

An electric field is used for treatment during water filtration. It is able to separate individual groups of pollutants. This processing method is much cheaper than using replacement cartridges.

Electrical engineering

The use of an electric field has very interesting applications in electrical engineering. Thus, a method was developed from source to consumer. Until recently, all developments were theoretical and experimental in nature. There is already an effective implementation of the technology that plugs into the USB connector of a smartphone. This method does not yet allow the transfer of energy over a long distance, but it is being improved. It is quite possible that in the near future the need for charging cables with power supplies will disappear completely.

When performing electrical installation and repair work, LEDs are used, operating on the basis of a circuit. In addition to a number of functions, it can respond to an electric field. Thanks to this, when the probe approaches the phase wire, the indicator begins to glow without actually touching the conductive core. It reacts to the field emanating from the conductor even through insulation. The presence of an electric field allows you to find current-carrying wires in the wall, as well as determine their break points.

You can protect yourself from the effects of the electric field using a metal screen, which will not have it inside. This property is widely used in electronics to eliminate the mutual influence of electrical circuits that are located quite close to each other.

Possible future applications

There are also more exotic possibilities for the electric field, which science does not yet possess today. These are communications faster than the speed of light, teleportation of physical objects, movement in an instant between open locations (wormholes). However, to implement such plans will require much more complex research and experiments than conducting experiments with two possible outcomes.

However, science is constantly developing, opening up new possibilities for the use of electric fields. In the future, its scope of use may expand significantly. It is possible that it will find application in all significant areas of our lives.

The action of some charged bodies on other charged bodies is carried out without their direct contact, through an electric field.

The electric field is material. It exists independently of us and our knowledge about it.

An electric field is created by electric charges and is detected by electric charges by the action of a certain force on them.

The electric field propagates at a terminal speed of 300,000 km/s in a vacuum.

Since one of the main properties of the electric field is its effect on charged particles with a certain force, to introduce quantitative characteristics of the field it is necessary to place a small body with a charge q (test charge) at the point in space being studied. A force will act on this body from the field

If you change the size of the test charge, for example, by a factor of two, the force acting on it will also change by a factor of two.

When the value of the test charge changes by a factor of n, the force acting on the charge also changes by a factor of n.

The ratio of the force acting on a test charge placed at a given point of the field to the magnitude of this charge is a constant value and does not depend either on this force, or on the magnitude of the charge, or on whether there is any charge. This ratio is denoted by a letter and is taken as the force characteristic of the electric field. The corresponding physical quantity is called electric field strength .

Tension shows how much force is exerted by the electric field on a unit charge placed at a given point in the field.

To find the unit of tension, you need to substitute the units of force - 1 N and charge - 1 C into the defining equation of tension. We get: [ E ] = 1 N / 1 Cl = 1 N / Cl.

For clarity, electric fields in the drawings are depicted using field lines.

An electric field can do work to move a charge from one point to another. Hence, a charge placed at a given point in the field has a reserve of potential energy.

The energy characteristics of the field can be entered similarly to the introduction of the force characteristic.

When the size of the test charge changes, not only the force acting on it changes, but also the potential energy of this charge. The ratio of the energy of the test charge located at a given point in the field to the value of this charge is a constant value and does not depend on either the energy or the charge.

To obtain a unit of potential, it is necessary to substitute the units of energy - 1 J and charge - 1 C into the defining equation of potential. We get: [φ] = 1 J / 1 C = 1 V.

This unit has its own name: 1 volt.

The field potential of a point charge is directly proportional to the magnitude of the charge creating the field and inversely proportional to the distance from the charge to a given point in the field:

Electric fields in drawings can also be represented using surfaces of equal potential, called equipotential surfaces .

When an electric charge moves from a point with one potential to a point with another potential, work is done.

A physical quantity equal to the ratio of the work done to move a charge from one point in the field to another to the value of this charge is called electrical voltage :

Voltage shows how much work is done by an electric field when moving a charge of 1 C from one point in the field to another.

The unit of voltage, as well as potential, is 1 V.

The voltage between two field points located at a distance d from each other is related to the field strength:

In a uniform electric field, the work of moving a charge from one point of the field to another does not depend on the shape of the trajectory and is determined only by the magnitude of the charge and the potential difference between the points of the field.

Electromagnetic fields permeate the entire surrounding space.

There are natural and man-made sources of electromagnetic fields.

Natural electromagnetic field sources:

• atmospheric electricity;
• radio emission from the Sun and galaxies (relict radiation, uniformly distributed throughout the Universe);
• electric and magnetic fields of the Earth.

Sources man-made electromagnetic fields are various transmitting equipment, switches, high-frequency isolation filters, antenna systems, industrial installations equipped with high-frequency (HF), ultra-high-frequency (UHF) and ultra-high-frequency (microwave) generators.

Sources of electromagnetic fields in production

Sources of EMF in production include two large groups of sources:

The following may have a dangerous impact on workers:

• EMF radio frequencies (60 kHz - 300 GHz),
• electric and magnetic fields of industrial frequency (50 Hz);
• electrostatic fields.

Sources of radio frequency waves are primarily radio and television broadcasting stations. The classification of radio frequencies is given in table. 1. The effect of radio waves largely depends on the characteristics of their propagation. It is influenced by the nature of the relief and cover of the Earth's surface, large objects and buildings located on the path, etc. Forests and uneven terrain absorb and scatter radio waves.

Table 1. Radio frequency range

Electrostatic fields are created in power plants and electrical processes. Depending on the sources of formation, they can exist in the form of an electrostatic field itself (a field of stationary charges). In industry, electrostatic fields are widely used for electrogas purification, electrostatic separation of ores and materials, and electrostatic application of paints and polymer materials. Static electricity is generated during the manufacture, testing, transportation and storage of semiconductor devices and integrated circuits, grinding and polishing of cases of radio and television receivers, in the premises of computer centers, in areas of duplicating equipment, as well as in a number of other processes where dielectric materials are used. Electrostatic charges and the electrostatic fields they create can arise when dielectric liquids and some bulk materials move through pipelines, when dielectric liquids are poured, or when film or paper is rolled.

Magnetic fields are created by electromagnets, solenoids, capacitor-type installations, cast and cermet magnets, and other devices.

Sources of electric fields

Any electromagnetic phenomenon, considered as a whole, is characterized by two sides - electrical and magnetic, between which there is a close connection. The electromagnetic field also always has two interconnected sides - the electric field and the magnetic field.

Source of electric fields of industrial frequency are current-carrying parts of existing electrical installations (power lines, inductors, capacitors of thermal installations, feeder lines, generators, transformers, electromagnets, solenoids, half-wave or capacitor-type pulse units, cast and cermet magnets, etc.). Long-term exposure to an electric field on the human body can cause disruption of the functional state of the nervous and cardiovascular systems, which is expressed in increased fatigue, decreased quality of work operations, pain in the heart, changes in blood pressure and pulse.

For an electric field of industrial frequency, in accordance with GOST 12.1.002-84, the maximum permissible level of electric field strength, which is not allowed to remain in without the use of special protective equipment throughout the entire working day, is 5 kV/m. In the range from above 5 kV/m to 20 kV/m inclusive, the permissible residence time T (h) is determined by the formula T = 50/E - 2, where E is the strength of the acting field in the controlled area, kV/m. At field strengths above 20 kV/m to 25 kV/m, the time personnel stay in the field should not exceed 10 minutes. The maximum permissible value of the electric field strength is set to 25 kV/m.

If it is necessary to determine the maximum permissible electric field strength for a given time of stay in it, the intensity level in kV/m is calculated using the formula E - 50/(T + 2), where T is the time of stay in the electric field, hours.

The main types of collective protection against the influence of the electric field of industrial frequency currents are shielding devices - an integral part of the electrical installation, designed to protect personnel in open switchgear and on overhead power lines (Fig. 1).

A shielding device is necessary when inspecting equipment and during operational switching, monitoring work progress. Structurally, shielding devices are designed in the form of canopies, canopies or partitions made of metal ropes. rods, meshes. Shielding devices must have an anti-corrosion coating and be grounded.

Rice. 1. Screening canopy over the passage into the building

To protect against the influence of the electric field of industrial frequency currents, shielding suits are also used, which are made of special fabric with metallized threads.

Sources of electrostatic fields

Enterprises widely use and produce substances and materials that have dielectric properties, which contributes to the generation of static electricity charges.

Static electricity is produced by the friction (contact or separation) of two dielectrics against each other or dielectrics against metals. In this case, electrical charges can accumulate on the rubbing substances, which easily flow into the ground if the body is a conductor of electricity and it is grounded. Electrical charges are retained on dielectrics for a long time, which is why they are called static electricity.

The process of the emergence and accumulation of electrical charges in substances is called electrification.

The phenomenon of static electrification is observed in the following main cases:

• in flow and splashing of liquids;
• in a stream of gas or steam;
• upon contact and subsequent removal of two solid
• dissimilar bodies (contact electrification).

A discharge of static electricity occurs when the electrostatic field strength above the surface of a dielectric or conductor, due to the accumulation of charges on them, reaches a critical (breakdown) value. For air, the breakdown voltage is 30 kV/cm.

People working in areas exposed to electrostatic fields experience a variety of disorders: irritability, headache, sleep disturbance, decreased appetite, etc.

Permissible levels of electrostatic field strength are established by GOST 12.1.045-84 “Electrostatic fields. Permissible levels at workplaces and requirements for monitoring” and Sanitary and Hygienic Standards for Permissible Electrostatic Field Strength (GN 1757-77).

These regulations apply to electrostatic fields created during the operation of high-voltage direct current electrical installations and electrification of dielectric materials, and establish permissible levels of electrostatic field strength at personnel workplaces, as well as general requirements for control and protective equipment.

Permissible levels of electrostatic field strength are established depending on the time spent at work places. The maximum permissible level of electrostatic field strength is 60 kV/m for 1 hour.

When the electrostatic field strength is less than 20 kV/m, the time spent in electrostatic fields is not regulated.

In the voltage range from 20 to 60 kV/m, the permissible time for personnel to remain in an electrostatic field without protective equipment depends on the specific level of tension in the workplace.

Measures to protect against static electricity are aimed at preventing the occurrence and accumulation of static electricity charges, creating conditions for the dispersion of charges and eliminating the danger of their harmful effects. Basic protective measures:

• preventing the accumulation of charges on electrically conductive parts of equipment, which is achieved by grounding equipment and communications on which charges may appear (devices, tanks, pipelines, conveyors, drainage devices, overpasses, etc.);
• reducing the electrical resistance of processed substances;
• the use of static electricity neutralizers that create positive and negative ions near electrified surfaces. Ions carrying a charge opposite to the surface charge are attracted to it and neutralize the charge. Based on their operating principle, neutralizers are divided into the following types: corona discharge(induction and high voltage), radioisotope, the action of which is based on the ionization of air by alpha radiation of plutonium-239 and beta radiation of promethium-147, aerodynamic, which are an expansion chamber in which ions are generated using ionizing radiation or a corona discharge, which are then supplied by air flow to the place where static electricity charges are formed;
• reducing the intensity of static electricity charges. It is achieved by appropriate selection of the speed of movement of substances, excluding splashing, crushing and atomization of substances, removal of electrostatic charge, selection of friction surfaces, purification of flammable gases and liquids from impurities;
• removal of static electricity charges that accumulate on people. This is achieved by providing workers with conductive shoes and antistatic gowns, installing electrically conductive floors or grounded zones, platforms and work platforms. grounding of door handles, handrails of stairs, handles of devices, machines and apparatus.

Magnetic field sources

Magnetic fields (MF) of industrial frequency arise around any electrical installations and conductors of industrial frequency. The greater the current, the higher the intensity of the magnetic field.

Magnetic fields can be constant, pulsed, infra-low frequency (with a frequency of up to 50 Hz), variable. The action of MP can be continuous or intermittent.

The degree of impact of the magnetic field depends on its maximum intensity in the working space of the magnetic device or in the zone of influence of the artificial magnet. The dose received by a person depends on the location of the workplace in relation to the MP and the work regime. Constant MP does not cause any subjective effects. When exposed to variable MFs, characteristic visual sensations, so-called phosphenes, are observed, which disappear when the effect ceases.

When constantly working under conditions of exposure to MFs exceeding the maximum permissible levels, dysfunctions of the nervous, cardiovascular and respiratory systems, the digestive tract, and changes in blood composition develop. With predominantly local exposure, vegetative and trophic disorders may occur, usually in the area of ​​the body that is under the direct influence of the MP (most often the hands). They are manifested by a feeling of itching, pallor or bluishness of the skin, swelling and thickening of the skin, in some cases hyperkeratosis (keratinization) develops.

The MF voltage at the workplace should not exceed 8 kA/m. The MF voltage of a power transmission line with voltage up to 750 kV usually does not exceed 20-25 A/m, which does not pose a danger to humans.

Sources of electromagnetic radiation

Sources of electromagnetic radiation in a wide range of frequencies (micro- and low-frequency, radio frequency, infrared, visible, ultraviolet, X-ray - Table 2) are powerful radio stations, antennas, microwave generators, induction and dielectric heating installations, radars, lasers, measuring and controlling devices, research facilities, medical high-frequency instruments and devices, personal electronic computers (PCs), video display terminals on cathode ray tubes, used both in industry, scientific research, and in everyday life.

Sources of increased danger from the point of view of electromagnetic radiation are also microwave ovens, televisions, mobile and radiotelephones.

Table 2. Spectrum of electromagnetic radiation

Low frequency emissions

Sources of low-frequency radiation are production systems. transmission and distribution of electricity (power plants, transformer substations, power transmission systems and lines), electrical networks of residential and administrative buildings, transport powered by electric drives and its infrastructure.

With prolonged exposure to low-frequency radiation, headaches, changes in blood pressure, fatigue, hair loss, brittle nails, weight loss, and a persistent decrease in performance may occur.

To protect against low-frequency radiation, either radiation sources (Fig. 2) or areas where a person may be are shielded.

Rice. 2. Shielding: a - inductor; b - capacitor

RF Sources

The sources of radio frequency EMF are:

• in the range 60 kHz - 3 MHz - unshielded elements of equipment for induction processing of metal (pumping, annealing, melting, soldering, welding, etc.) and other materials, as well as equipment and instruments used in radio communications and broadcasting;
• in the range of 3 MHz - 300 MHz - unshielded elements of equipment and devices used in radio communications, radio broadcasting, television, medicine, as well as equipment for heating dielectrics;
• in the range 300 MHz - 300 GHz - unshielded elements of equipment and devices used in radar, radio astronomy, radio spectroscopy, physiotherapy, etc. Long-term exposure to radio waves on various systems of the human body causes different consequences.

The most characteristic deviations in the human central nervous system and cardiovascular system when exposed to radio waves of all ranges are. Subjective complaints - frequent headaches, drowsiness or insomnia, fatigue, weakness, increased sweating, memory loss, confusion, dizziness, darkening of the eyes, causeless feelings of anxiety, fear, etc.

The influence of an electromagnetic field in the mid-wave range with prolonged exposure is manifested in excitatory processes and disruption of positive reflexes. Changes in the blood are noted, including leukocytosis. Liver dysfunction and dystrophic changes in the brain, internal organs and reproductive system have been established.

The short-wave electromagnetic field provokes changes in the adrenal cortex, the cardiovascular system, and the bioelectric processes of the cerebral cortex.

VHF EMF causes functional changes in the nervous, cardiovascular, endocrine and other systems of the body.

The degree of danger of exposure to microwave radiation to a person depends on the power of the source of electromagnetic radiation, the operating mode of the emitters, the design features of the emitting device, EMF parameters, energy flux density, field strength, exposure time, size of the irradiated surface, individual properties of a person, location of workplaces and efficiency protective measures.

There are thermal and biological effects of microwave radiation.

Thermal effects are a consequence of the absorption of energy from EMF microwave radiation. The higher the field strength and the longer the exposure time, the stronger the thermal effect. When the energy flux density W is 10 W/m2, the body cannot cope with heat removal, body temperature rises and irreversible processes begin.

Biological (specific) effects manifest themselves in a weakening of the biological activity of protein structures, disruption of the cardiovascular system and metabolism. This effect occurs when the EMF intensity is less than the thermal threshold, which is 10 W/m2.

Exposure to EMF microwave radiation is especially harmful to tissues with an underdeveloped vascular system or insufficient blood circulation (eyes, brain, kidneys, stomach, gall bladder and bladder). Exposure to the eyes can cause clouding of the lens (cataracts) and burns to the cornea.

To ensure safety when working with sources of electromagnetic waves, systematic monitoring of actual standardized parameters is carried out at workplaces and in places where personnel may be located. Control is carried out by measuring the electric and magnetic field strength, as well as measuring the energy flux density.

Protection of personnel from exposure to radio waves is used for all types of work if the working conditions do not meet the requirements of the standards. This protection is carried out in the following ways:

• matched loads and power absorbers that reduce the strength and density of the electromagnetic wave energy flow field;
• shielding of the workplace and radiation source;
• rational placement of equipment in the workroom;
• selection of rational modes of operation of equipment and labor modes of personnel.

The most effective use of matched loads and power absorbers (antenna equivalents) is in the manufacture, configuration and testing of individual units and equipment complexes.

An effective means of protection against exposure to electromagnetic radiation is to shield radiation sources and the workplace using screens that absorb or reflect electromagnetic energy. The choice of screen design depends on the nature of the technological process, source power, and wave range.

Reflective screens are made from materials with high electrical conductivity, such as metals (in the form of solid walls) or cotton fabrics with a metal backing. Solid metal screens are the most effective and already at a thickness of 0.01 mm provide attenuation of the electromagnetic field by approximately 50 dB (100,000 times).

For the manufacture of absorbing screens, materials with poor electrical conductivity are used. Absorbing screens are made in the form of pressed sheets of rubber of a special composition with conical solid or hollow spikes, as well as in the form of plates of porous rubber filled with carbonyl iron, with a pressed metal mesh. These materials are glued to the frame or surface of the radiating equipment.

An important preventive measure for protection from electromagnetic radiation is compliance with the requirements for the placement of equipment and for the creation of premises in which sources of electromagnetic radiation are located.

Protection of personnel from overexposure can be achieved by placing HF, UHF and microwave generators, as well as radio transmitters in specially designed rooms.

Screens of radiation sources and workplaces are blocked with disconnecting devices, which makes it possible to prevent the operation of emitting equipment when the screen is open.

Permissible levels of exposure to workers and requirements for monitoring at workplaces for electromagnetic fields of radio frequencies are set out in GOST 12.1.006-84.

A constant electrostatic field (ESF) is a field of stationary electric charges that interacts between them

Static current is a set of phenomena associated with the emergence and maintenance of a free electric charge on the surface and in the volume of dielectric and semiconductor substances, materials, products or insulated conductors.

The emergence of static electricity charges occurs during deformation, crushing of substances, relative movement of two bodies in contact, layers of liquid and bulk materials, with intense mixing, crystallization, and also due to ind.

ESP is characterized by tension (B). Tension. ESP is the ratio of the force acting in a field on a point electric charge to the magnitude of this charge. The unit of measurement of tension. ESP is volts per meter (V/m mm).

ESP is created in power plants and during electrical processes, depending on the source of formation, they can exist in the form of their own electrostatic field (field of stationary charges) or stationary electric field (direct current electric field).

Where are ESPs used?

ESPs are widely used in electrogas purification, electrostatic separation of materials, electrostatic application of paints and polymers and in other production processes.

In the radio-electronic industry, static current is generated during transportation, grinding, polishing of radio and television receivers, in the premises of computer centers, as well as in other processes where dielectric materials are used, which are a by-product and undesirable production factor.

ESP, which occurs during the processing of chemical fiber, has high dielectric properties. Level of tension. ESP on spinning and weaving equipment reaches 20-60 kV/m

In the chemical industry, during the production of plastic materials and products made from them (tire cord, linoleum, etc.), electrostatic charges and fields with a strength of 240-250 kV/m are formed

How does ESP affect the human body?

Biological action. ESP on the human body determines the greatest sensitivity to electrostatic fields of the nervous, cardiovascular, neurohumoral and other body systems

Workers working in the area of ​​the electric field experience various complaints of irritability, headache, sleep disturbance, loss of appetite, etc.

In affected people. ESP is characterized by the appearance of peculiar “phobias” caused by the fear of waiting for a discharge. The tendency to "phobias" is mainly accompanied by increased emotional excitability

How is hygienic regulation of electrostatic fields carried out?

The electrostatic field strength is standardized by the standard. GOST 121045-84 "Electrostatic fields. Permissible levels in the workplace and requirements for monitoring"

The above standard applies to. ESP arising during the operation of high voltage DC electrical equipment and electrification of dielectric materials. This standard establishes additional permissible levels of electrostatic field strength in workplaces, as well as general requirements for monitoring and protective equipment.

Acceptable tension levels. ESPs are established depending on the time spent at work places

Maximum permissible level of tension. ESP (E, ra") is accepted according to the standard 60 kV/m for one hour

If the electrostatic field strength is up to 20 kV/m, the residence time is c. ESP is not regulated

In the voltage range from 20 to 60 kV/m, the permissible stay time for workers is. ESP without protective equipment (/, year) is determined by the formula:

Where. E^ - actual value of tension. ESP, kV/m

To determine tension. ESP used electrostatic field strength meter

What protective means are there against exposure to ESP?

The use of protective equipment for workers is mandatory in cases where actual tension levels exist. ESP at workplaces exceeds 60 kV/m

To protect against exposure. ESPs are used: shielding of workplace field sources, static shock neutralizers, limiting operating time, etc.

When choosing means of protection against static electricity, the features of technological processes, the physico-chemical properties of the materials being processed, the microclimate of production premises, etc. must be taken into account. The above factors determine a differentiated approach to the development of protective means.

Reducing the generation of electrostatic charges or removing them from electrified materials is achieved by:

1) grounding of metal and electrically conductive elements of technological equipment;

2) increase in surface area and volumetric conductivity of dielectrics;

3) installation of static electricity neutralizers

Protective grounding is carried out regardless of the use of other protection methods. Not only elements of process equipment are subject to grounding, but... And isolated electrically conductive sections of process equipment.

A fairly effective means of protection is to increase air humidity to 65-75%, if this is possible under the conditions of the technological process

Among the personal protective equipment, antistatic shoes, antistatic gowns, overalls, grounded bracelets to protect hands and other means that can provide electrostatic grounding to the human body are used.

Electrostatic field electrostatic field

electric field of stationary electric charges.

ELECTROSTATIC FIELD

ELECTROSTATIC FIELD, an electric field of stationary electric charges that do not change over time, which carries out the interaction between them.
An electrostatic field is characterized by the electric field strength (cm. ELECTRIC FIELD STRENGTH) E, which is its force characteristic: The electrostatic field strength shows with what force the electrostatic field acts on a unit positive electric charge (cm. ELECTRIC CHARGE), placed at a given point in the field. The direction of the tension vector coincides with the direction of the force acting on the positive charge, and is opposite to the direction of the force acting on the negative charge.
An electrostatic field is stationary (constant) if its strength does not change over time. Stationary electrostatic fields are created by stationary electric charges.
An electrostatic field is homogeneous if its intensity vector is the same at all points of the field; if the intensity vector at different points is different, the field is inhomogeneous. Uniform electrostatic fields are, for example, the electrostatic fields of a uniformly charged finite plane and a flat capacitor (cm. CONDENSER (electric)) away from the edges of its covers.
One of the fundamental properties of the electrostatic field is that the work of the electrostatic field forces when moving a charge from one point in the field to another does not depend on the trajectory of movement, but is determined only by the position of the starting and ending points and the magnitude of the charge. Consequently, the work done by the electrostatic field forces when moving a charge along any closed trajectory is equal to zero. Force fields that have this property are called potential or conservative. That is, an electrostatic field is a potential field, the energy characteristic of which is the electrostatic potential (cm. ELECTROSTATIC POTENTIAL), associated with the tension vector E by the relation:
E = -gradj.
Lines of force are used to graphically represent the electrostatic field. (cm. POWER LINES)(tension lines) - imaginary lines, the tangents to which coincide with the direction of the tension vector at each point of the field.
For electrostatic fields, the principle of superposition is observed (cm. SUPERPOSITION PRINCIPLE). Each electric charge creates an electric field in space regardless of the presence of other electric charges. The strength of the resulting field created by a system of charges is equal to the geometric sum of the field strength created at a given point by each of the charges separately.
Any charge in the space surrounding it creates an electrostatic field. To detect a field at any point, it is necessary to place a point test charge at the observation point - a charge that does not distort the field under study (does not cause a redistribution of charges creating the field).
The field created by a solitary point charge q is spherically symmetric. Tension modulus of a solitary point charge in vacuum using Coulomb's law (cm. COULLONA LAW) can be represented as:
E = q/4pe o r 2.
Where e o is the electrical constant, = 8.85. 10 -12 f/m.
Coulomb's law, established using the torsional balances he created (see Coulomb balances (cm. PENDANT SCALES)), is one of the basic laws describing the electrostatic field. He establishes a relationship between the force of interaction of charges and the distance between them: the force of interaction between two point-like stationary charged bodies in a vacuum is directly proportional to the product of the charge moduli and inversely proportional to the square of the distance between them.
This force is called Coulomb force, and the field is called Coulomb force. In a Coulomb field, the direction of the vector depends on the sign of the charge Q: if Q > 0, then the vector is directed radially away from the charge, if Q ( cm. DIELECTRIC CONTINUITY) of the medium) is less than in vacuum.
The experimentally established Coulomb law and the superposition principle make it possible to fully describe the electrostatic field of a given system of charges in a vacuum. However, the properties of the electrostatic field can be expressed in another, more general form, without resorting to the idea of ​​a Coulomb field of a point charge. The electric field can be characterized by the flux value of the electric field strength vector, which can be calculated in accordance with Gauss's theorem (cm. GAUSS'S THEOREM). Gauss's theorem establishes a relationship between the flow of electric field strength through a closed surface and the charge within that surface. The intensity flow depends on the field distribution over the surface of a particular area and is proportional to the electric charge inside this surface.
If an insulated conductor is placed in an electric field, then a force will act on the free charges q in the conductor. As a result, a short-term movement of free charges occurs in the conductor. This process will end when the own electric field of the charges arising on the surface of the conductor completely compensates for the external field, i.e., an equilibrium distribution of charges is established, in which the electrostatic field inside the conductor becomes zero: at all points inside the conductor E = 0, then there is a field missing. The electrostatic field lines outside the conductor in close proximity to its surface are perpendicular to the surface. If this were not so, then there would be a field strength component, and current would flow along the surface of the conductor and along the surface. Charges are located only on the surface of the conductor, while all points on the surface of the conductor have the same potential value. The surface of the conductor is an equipotential surface (cm. EQUIPOTENTIAL SURFACE). If there is a cavity in the conductor, then the electric field in it is also zero; This is the basis for electrostatic protection of electrical devices.
If a dielectric is placed in an electrostatic field, then a polarization process occurs in it - the process of dipole orientation (cm. DIPOLE) or the appearance of field-oriented dipoles under the influence of an electric field. In a homogeneous dielectric, the electrostatic field due to polarization (see Polarization of dielectrics) decreases in? once.

encyclopedic Dictionary. 2009 .

See what an “electrostatic field” is in other dictionaries:

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• New ideas in physics. Vol. 3. The principle of relativity. 1912, Borgman I.I. The wave theory of the holy considers the phenomenon of the holy to be caused by vibrations propagating in the form of waves in the space surrounding the holy body; since very soon* it became clear... Category: Mathematics and science Series: Publisher: YOYO Media,