The electric field can be considered as mathematical model, describing the value of the electric field strength at a given point in space. Douglas Giancoli wrote: “It should be emphasized that the field is not some kind of substance; or rather, it is an extremely useful concept... The question of “reality” and the existence of the electric field is actually a philosophical, rather even metaphysical question. In physics, the concept of field has proven to be extremely useful - it is one of the greatest achievements human mind."

The electric field is one of the components of a single electromagnetic field and the manifestation of electromagnetic interaction.

Physical properties of the electric field

Field effect - The field effect is that when an electric field is applied to the surface of an electrically conducting medium, the concentration in its near-surface layer changes free media charge. This effect underlies the operation of field-effect transistors.

The main effect of the electric field is the force effect on stationary (relative to the observer) electrically charged bodies or particles. If a charged body is fixed in space, then it does not accelerate under the influence of force. The magnetic field (the second component of the Lorentz force) also exerts a force on moving charges.

Observing the electric field in everyday life

An electric field often occurs near the television screen when the television receiver is turned on or off. This field can be felt by its effect on the hairs on the hands or face.

What is an electric field?

Let's hang a charged cartridge case on a thread and bring an electrified glass rod to it. Even in the absence of direct contact, the sleeve on the thread deviates from the vertical position, being attracted to the stick (Fig. 13).

Charged bodies, as we see, are able to interact with each other at a distance. How is the action transmitted from one of these bodies to another? Maybe it's all about the air between them? Let's find out this by experience.

Let's place a charged electroscope (with the glasses removed) under the bell of the air pump, and then pump out the air from under it. We will see that in airless space the leaves of the electroscope will continue to repel each other (Fig. 14). This means that air does not participate in the transmission of electrical interaction. Then by what means does the interaction of charged bodies take place? The answer to this question was given in their works by the English scientists M. Faraday (1791-1867) and J. Maxwell (1831-1879).

According to the teachings of Faraday and Maxwell, the space surrounding a charged body differs from the space around unelectrified bodies. There is an electric field around charged bodies. This field is used to electrical interaction.

Electrical field represents special kind matter, distinct from matter and existing around any charged bodies.

It is impossible to see it or touch it. The existence of an electric field can be judged only by its actions.

Basic properties of the electric field

Simple experiments allow us to establish basic properties of the electric field.

1. The electric field of a charged body acts with some force on any other charged body that finds itself in this field.

This is evidenced by all experiments on the interaction of charged bodies. So, for example, a charged sleeve that found itself in the electric field of an electrified stick (see Fig. 13) was subjected to the force of attraction towards it.

2. Near charged bodies, the field they create is stronger, and farther away it is weaker.

To verify this, let us again turn to the experiment with a charged cartridge case (see Fig. 13). Let's start bringing the stand with the cartridge case closer to the loaded stick. We will see that as the sleeve approaches the stick, the angle of deviation of the thread from the vertical will become larger and larger (Fig. 15). An increase in this angle indicates that the closer the sleeve is to the source of the electric field (electrified rod), the more greater strength this field acts on her. This means that near a charged body the field it creates is stronger than at a distance.

It should be borne in mind that not only a charged stick acts on a charged sleeve with its electric field, but also the sleeve, in turn, acts on the stick with its electric field. It is in such mutual action on each other that the electrical interaction charged bodies.

The electric field also manifests itself in experiments with dielectrics. When a dielectric is in an electric field, the positively charged parts of its molecules (atomic nuclei) are shifted in one direction under the influence of the field, and the negatively charged parts (electrons) are shifted in the other direction. This phenomenon is called dielectric polarization. It is polarization that explains the simplest experiments on the attraction of light pieces of paper by an electrified body. These pieces are generally neutral. However, in the electric field of an electrified body (for example, a glass rod), they become polarized. On the surface of the piece that is closer to the stick, a charge appears that is opposite in sign to the charge of the stick. Interaction with it leads to the attraction of pieces of paper to the electrified body.

Electric power

The force with which an electric field acts on a charged body (or particle) is called electrical force:

Fel- electric force.

Under the influence of this force, a particle caught in an electric field acquires acceleration A, which can be determined using Newton's second law:

Where m is the mass of a given particle.

Since the time of Faraday, it has been customary to use power lines.

Electric field lines- these are lines indicating the direction of the force acting in this field on a positively charged particle placed in it. The field lines created by a positively charged body are shown in Figure 16, a. Figure 16, b shows the field lines created by a negatively charged body.

A similar picture can be observed using a simple device called electric plume. By giving him a charge, we will see how all his paper strips disperse into different sides and will be located along the electric field lines (Fig. 17).

When a charged particle enters an electric field, its speed in this field can either increase or decrease. If the charge of a particle q>0, then when moving along the lines of force it will accelerate, and when moving in opposite direction brake. If the particle charge q<0, то все будет наоборот ее скорость будет уменьшаться при движении в направлении силовых линий и увеличиваться при движении в противоположном направлении.

It's interesting to know

From today's topic about the electric field, we learned that it exists in the space that is located around the electric charge.

Let's see how, using directional lines of force, we can depict this electric field using graphs:

You might be interested to know that electric fields of varying strengths operate in our atmosphere. If we consider the electric field from the point of view of the universe, then usually the Earth has a negative charge, but the bottom of the clouds is positive. And charged particles such as ions are contained in the air and its content varies depending on various factors. These factors depend both on the time of year and on weather conditions and the frequency of the atmosphere.

And since the atmosphere is permeated with these particles, which, being in continuous movement and characterized by changes either into positive or negative ions, tend to affect human well-being and health. And the most interesting thing is that a large predominance of positive ions in the atmosphere can cause unpleasant sensations in our body.

Biological effect of the electromagnetic field

Now let’s talk to you about the biological effect of EMF on human health and its impact on living organisms. It turns out that living organisms that are in the zone of influence of the electromagnetic field are subject to strong factors of its influence.

Long-term exposure to an electromagnetic field has a negative impact on a person’s health and well-being. For example, in a person with allergic diseases, such exposure to EMF can cause an attack of epilepsy. And if a person stays in an electromagnetic field for a longer period of time, diseases not only of the cardiovascular and nervous systems can develop, but also cause cancer.

Scientists have proven that where there is a strong electric field, behavioral changes can be observed in insects. This negative impact can manifest itself in the form of aggression, anxiety and decreased performance.

Under such influence, abnormal development can also be observed among plants. Under the influence of an electromagnetic field, plants can change in size, shape and number of petals.

Interesting Facts Related to Electricity

Discoveries in the field of electricity are one of the most important achievements of man, because modern life without this discovery is now difficult to even imagine.

Did you know that in some areas of Africa and South America there are villages where electricity is still not available? And do you know how people get out of this situation? It turns out that they illuminate their homes with the help of insects such as fireflies. They fill glass jars with these insects and use fireflies to get light.

Do you know about the ability of bees to accumulate a positive charge of electricity during flight? But flowers have a negative electrical charge, and thanks to this, their pollen itself is attracted to the bee’s body. But the most interesting thing is that the field of such contact between a bee and a flower, the plant’s electric field changes and, as it were, gives a signal to other bees about the absence of pollen on this plant.

But in the world of fish, the most famous electric hunters are stingrays. To neutralize its prey, the stingray uses electrical discharges to paralyze it.

Did you know that electric eels have the strongest electrical discharge? These freshwater fish have a current discharge voltage that can reach 800 V.

Homework

1. What is an electric field?
2. How does a field differ from matter?
3. List the main properties of the electric field.
4. What do electric field lines indicate?
5. How is the acceleration of a charged particle moving in an electric field found?
6. In what case does an electric field increase the speed of a particle and in what case does it decrease it?
7. Why are neutral pieces of paper attracted to an electrified body?
8. Explain why, after charging the electric sultan, its paper strips diverge in different directions.

Experimental task.

Electricize the comb on your hair, then touch it to a small piece of cotton wool (fluff). What will happen to the cotton wool? Shake the fluff from the comb and, when it is in the air, make it float at the same height by placing an electrified comb from below at some distance. Why does the fluff stop falling? What will keep her in the air?

S.V. Gromov, I.A. Rodina, Physics 9th grade

Let's hang a charged cartridge case on a thread and bring an electrified glass rod to it. Even in the absence of direct contact, the sleeve on the thread deviates from the vertical position, being attracted to the stick (Fig. 13).

Charged bodies, as we see, are able to interact with each other at a distance. How is the action transmitted from one of these bodies to another? Maybe it's all about the air between them? Let's find out this by experience.

Let's place a charged electroscope (with the glasses removed) under the bell of the air pump, and then pump out the air from under it. We will see that in airless space the leaves of the electroscope will still repel each other (Fig. 14). This means that air does not participate in the transmission of electrical interaction. Then by what means does the interaction of charged bodies take place? The answer to this question was given in their works by the English scientists M. Faraday (1791-1867) and J. Maxwell (1831-1879).

According to the teachings of Faraday and Maxwell, the space surrounding a charged body differs from the space around unelectrified bodies. There is an electric field around charged bodies. With the help of this field, electrical interaction is carried out.

Electric field is a special type of matter, different from matter and existing around any charged bodies.

It is impossible to see it or touch it. The existence of an electric field can be judged only by its actions.

Simple experiments allow us to establish basic properties of the electric field.

1. The electric field of a charged body acts with some force on any other charged body that finds itself in this field.

This is evidenced by all experiments on the interaction of charged bodies. So, for example, a charged sleeve that found itself in the electric field of an electrified stick (see Fig. 13) was subjected to the force of attraction towards it.

2. Near charged bodies, the field they create is stronger, and farther away it is weaker.

To verify this, let us again turn to the experiment with a charged cartridge case (see Fig. 13). Let's start bringing the stand with the cartridge case closer to the loaded stick. We will see that as the sleeve approaches the stick, the angle of deviation of the thread from the vertical will become larger and larger (Fig. 15). An increase in this angle indicates that the closer the sleeve is to the source of the electric field (an electrified rod), the greater the force this field acts on it. This means that near a charged body the field it creates is stronger than at a distance.

It should be borne in mind that not only a charged stick acts on a charged sleeve with its electric field, but also the sleeve, in turn, acts on the stick with its electric field. It is in this mutual action on each other that the electrical interaction of charged bodies is manifested.

The electric field also manifests itself in experiments with dielectrics. When a dielectric is exposed to an electric field, the positively charged parts of its molecules ( atomic nuclei) under the influence of the field are shifted in one direction, and the negatively charged parts (electrons) are shifted in the other direction. This phenomenon is called dielectric polarization. It is polarization that explains the simplest experiments on the attraction of light pieces of paper by an electrified body. These pieces are generally neutral. However, in the electric field of an electrified body (for example, a glass rod), they become polarized. On the surface of the piece that is closer to the stick, a charge appears that is opposite in sign to the charge of the stick. Interaction with it leads to the attraction of pieces of paper to the electrified body.

The force with which an electric field acts on a charged body (or particle) is called electrical force:

F el - electric force.

Under the influence of this force, a particle caught in an electric field acquires acceleration a, which can be determined using Newton’s second law:

a = F el / m (6.1)

where m is the mass of a given particle.

Since the time of Faraday, it has been customary to use field lines to graphically represent the electric field.

These are lines indicating the direction of the force acting in this field on a positively charged particle placed in it. The field lines created by a positively charged body are shown in Figure 16, a. Figure 16, b shows the field lines created by a negatively charged body.


A similar picture can be observed using a simple device called an electric plume. Having given it a charge, we will see how all its paper strips will disperse in different directions and will be located along the electric field lines (Fig. 17).

When a charged particle enters an electric field, its speed in this field can either increase or decrease. If the charge of a particle q>0, then when moving along the lines of force it will accelerate, and when moving in the opposite direction it will slow down. If the particle charge q< 0, то все будет наоборот ее скорость будет уменьшаться при движении в направлении силовых линий и увеличиваться при движении в противоположном направлении.

1. What is an electric field? 2. How does a field differ from matter? 3. List the main properties of the electric field. 4. What do electric field lines indicate? 5. How is the acceleration of a charged particle moving in an electric field found? 6. In what case does an electric field increase the speed of a particle and in what case does it decrease it? 7. Why are neutral pieces of paper attracted to an electrified body? 8. Explain why, after charging the electric sultan, its paper strips diverge in different directions.

Experimental task. Electricize the comb on your hair, then touch it to a small piece of cotton wool (fluff). What will happen to the cotton wool? Shake the fluff from the comb and, when it is in the air, make it float at the same height by placing an electrified comb from below at some distance. Why does the fluff stop falling? What will keep her in the air?

An electric field arises around a charge or charged body in space. In this field, any charge is affected by the electrostatic Coulomb force. A field is a form of matter that transmits force interactions between macroscopic bodies or particles that make up the substance. In an electrostatic field, the force interaction of charged bodies occurs. An electrostatic field is a stationary electric field and is a special case of an electric field created by stationary charges.

The electric field is characterized at each point in space by two characteristics: force - the vector of electrical intensity and energy - potential, which is a scalar quantity. The strength of a given point of the electric field is called the vector physical quantity, numerically equal and coinciding in direction with the force acting from the field on a unit positive charge placed at the field point under consideration:

An electric field line is a line whose tangents at each point determine the directions of the intensity vectors of the corresponding points of the electric field. The number of field lines passing through a unit area normal to these lines is numerically equal to the magnitude of the electric field strength vector at the center of this area. Tension lines electrostatic field begin on a positive charge and go to infinity for the field created by this charge. For the field being created negative charge, lines of force come from infinity to the charge.

The electrostatic field potential at a given point is called scalar quantity, numerically equal potential energy single positive charge, placed this point fields:

The work that is done by the forces of the electrostatic field when moving a point electric charge is equal to the product of this charge and the potential difference between the starting and ending points of the path:

where and are the potentials of the initial and end points fields when moving a charge.

The tension is related to the potential of the electrostatic field by the relation:

The potential gradient indicates the direction of the fastest change in potential when moving in a direction perpendicular to a surface of equal potential.

The field strength is numerically equal to the change in potential per unit length , measured in the direction perpendicular to the surface of equal potential, and directed in the direction of its decrease (minus sign):

Geometric place points of the electric field whose potentials are the same is called an equipotential surface or surface of equal potential. The intensity vector of each point of the electric field is normal to the equipotential surface drawn through this point. In Fig. 1 graphically shows the electric field formed by a positive point charge and a negatively charged plane R.

Solid lines equipotential surfaces with potentials , , etc., dotted lines are field lines, their direction is shown by an arrow.

What allows us to say that there is an electric field around a charged body?

• The presence of electromagnetic voltage and vortex fields.
• the effect of an electric field on a charge.
  simple experience:
  1. take a wooden stick and tie a sleeve made from a shiny chocolate wrapper to it with a silk thread.
  2. rubbing the handle on hair or wool
  3. bring the handle to the sleeve - the sleeve will deviate
  this allows us to assert that around a charged body (in in this case pens, there is an electric field)))
• someone help me solve this problem
  http://otvet.mail.ru/question/94520561
• everything is in the textbook)
• Link (electrono.ru Electric field strength, electric...)
  - In the space around an electrically charged body there is an electric field, which is one of the types of matter. The electric field has a reserve electrical energy, which appears in the form electrical forces, acting on charged bodies in the field.
  The electric field is conventionally depicted in the form of electric lines of force, which show the directions of action of the electric forces created by the electric field.
  Electric lines of force diverge in different directions from positively charged bodies and converge at bodies with a negative charge. The field created by two flat oppositely charged parallel plates is called uniform.
  The electric field can be made visible by placing gypsum particles suspended in liquid oil into it: they rotate along the field, positioning themselves along its power lines. A uniform field is an electric field in which the intensity is the same in magnitude and direction at all points in space.

  Wikipedia: For quantification electric field, a force characteristic is introduced - the electric field strength - a vector physical quantity, equal to the ratio the force with which the field acts on a positive test charge placed at a given point in space, to the magnitude of this charge. The direction of the tension vector coincides at each point in space with the direction of the force acting on the positive test charge.
  The field between two oppositely charged flat metal plates is approximately uniform. In a uniform electric field, the tension lines are directed parallel to each other.

• Recharge yourself and pour some fluff out of your pillow. Everything will be very clear.
• If you bring another electrically charged object to the first one, it will also be electric. charged object, then you can see their interaction, which proves the existence of an electric field.
• Allows you to calculate the laws of physics
• An electric field is a special form of matter that exists around bodies or particles with an electric charge, as well as in free form in electromagnetic waves. The electric field is directly invisible, but can be observed by its action and with the help of instruments. The main effect of the electric field is the acceleration of bodies or particles with an electric charge.

  The electric field can be considered as a mathematical model that describes the value of the electric field strength at a given point in space. Douglas Giancoli wrote: “It should be emphasized that the field is not some kind of substance; or rather, it is an extremely useful concept... The question of “reality” and the existence of the electric field is actually a philosophical, rather even metaphysical question. In physics, the concept of field has proven extremely useful - it is one of the greatest achievements of the human mind."

  The electric field is one of the components of a single electromagnetic field and a manifestation of electromagnetic interaction.

  Physical properties of the electric field
  At present, science has not yet achieved an understanding of the physical essence of fields such as electric, magnetic and gravitational, as well as their interaction with each other. So far, the results of their mechanical effects on charged bodies have only been described, and there is also a theory of electromagnetic waves described by Maxwell’s Equations.

  Field effect - The field effect is that when an electric field is applied to the surface of an electrically conducting medium, the concentration of free charge carriers in its near-surface layer changes. This effect underlies the operation of field-effect transistors.

  The main effect of the electric field is the force effect on stationary (relative to the observer) electrically charged bodies or particles. If a charged body is fixed in space, then it does not accelerate under the influence of force. The magnetic field (the second component of the Lorentz force) also exerts a force on moving charges.

  Observing the electric field in everyday life
  In order to create an electric field, it is necessary to create an electric charge. Rub some dielectric on wool or something similar, such as a plastic pen on your own hair. A charge will be created on the handle, and an electric field will be created around it. A charged pen will attract small pieces of paper. If you rub a larger object, such as a rubber band, on wool, then in the dark you will be able to see small sparks resulting from electrical discharges.

  An electric field often occurs near the television screen when the television receiver is turned on or off. This field can be felt by its effect on the hairs on the hands or face.