Why you need the Earth's magnetic field, you will learn from this article.

What is the value of the earth's magnetic field?

First of all, it protects artificial satellites and the inhabitants of the planet from the action of particles from space. These include charged, ionized particles of the solar wind. When they enter our atmosphere, the magnetic field changes their trajectory and directs them along the field line.

In addition, we entered the era of new technologies thanks to our magnetic field. All modern, advanced devices that work using a variety of memory drives (disks, cards) depend directly on the magnetic field. Its tension and stability directly affects absolutely all information, computer systems, since all the information necessary for their proper operation is placed on magnetic media.

Therefore, we can say with confidence that the prosperity of modern civilization, the "viability" of its technologies closely depends on the state of the magnetic field of our planet.

What is the earth's magnetic field?

Earth's magnetic field is an area around the planet where magnetic forces act.

As for its origin, this issue has not yet been finally resolved. But most researchers are inclined to believe that our planet owes the presence of a magnetic field to the core. It consists of an inner solid part and an outer liquid part. The rotation of the Earth contributes to constant currents in the liquid core. And this leads to the emergence of a magnetic field around them.

Most of the planets in the solar system have magnetic fields to varying degrees. If they are placed in a row according to the decrease in the dipole magnetic moment, then the following picture will be obtained: Jupiter, Saturn, Earth, Mercury and Mars. The main reason for its occurrence is the presence of a liquid core.

We still remember about the magnetic field from school, that's just what it is, "pops up" in the memories of not everyone. Let's refresh what we've been through, and maybe tell you something new, useful and interesting.

Determination of the magnetic field

A magnetic field is a force field that acts on moving electric charges (particles). Due to this force field, objects are attracted to each other. There are two types of magnetic fields:

1. Gravitational - is formed exclusively near elementary particles and viruetsya in its strength based on the features and structure of these particles.
2. Dynamic, produced in objects with moving electric charges (current transmitters, magnetized substances).

For the first time, the designation of the magnetic field was introduced by M. Faraday in 1845, although its meaning was a little erroneous, since it was believed that both electric and magnetic effects and interactions are based on the same material field. Later in 1873, D. Maxwell "presented" the quantum theory, in which these concepts began to be separated, and the previously derived force field was called the electromagnetic field.

How does a magnetic field appear?

The magnetic fields of various objects are not perceived by the human eye, and only special sensors can fix it. The source of the appearance of a magnetic force field on a microscopic scale is the movement of magnetized (charged) microparticles, which are:

• ions;
• electrons;
• protons.

Their movement occurs due to the spin magnetic moment, which is present in each microparticle.

Magnetic field, where can it be found?

No matter how strange it may sound, but almost all objects around us have their own magnetic field. Although in the concept of many, only a pebble called a magnet has a magnetic field, which attracts iron objects to itself. In fact, the force of attraction is in all objects, it only manifests itself in a lower valence.

It should also be clarified that the force field, called magnetic, appears only under the condition that electric charges or bodies are moving.

Immovable charges have an electric force field (it can also be present in moving charges). It turns out that the sources of the magnetic field are:

• permanent magnets;
• mobile charges.

When connected to two parallel conductors of electric current, they will attract or repel, depending on the direction (polarity) of the connected current. This is explained by the appearance of a special kind of matter around these conductors. This matter is called the magnetic field (MF). Magnetic force is the force with which conductors act on each other.

The theory of magnetism arose in antiquity, in the ancient civilization of Asia. In Magnesia, in the mountains, they found a special rock, pieces of which could be attracted to each other. By the name of the place, this breed was called "magnets". A bar magnet contains two poles. Its magnetic properties are especially pronounced at the poles.

A magnet hanging on a thread will show the sides of the horizon with its poles. Its poles will be turned north and south. The compass works on this principle. Opposite poles of two magnets attract and like poles repel.

Scientists have found that a magnetized needle, located near the conductor, deviates when an electric current passes through it. This suggests that an MF is formed around it.

The magnetic field affects:

Moving electric charges.
Substances called ferromagnets: iron, cast iron, their alloys.

Permanent magnets are bodies that have a common magnetic moment of charged particles (electrons).

1 - South pole of the magnet
2 - North pole of the magnet
3 - MP on the example of metal filings
4 - Direction of the magnetic field

Field lines appear when a permanent magnet approaches a paper sheet on which a layer of iron filings is poured. The figure clearly shows the places of the poles with oriented lines of force.

Magnetic field sources

• Electric field that changes with time.
• mobile charges.
• permanent magnets.

We have known permanent magnets since childhood. They were used as toys that attracted various metal parts to themselves. They were attached to the refrigerator, they were built into various toys.

Electric charges that are in motion often have more magnetic energy than permanent magnets.

Properties

• The main distinguishing feature and property of the magnetic field is relativity. If a charged body is left motionless in a certain frame of reference, and a magnetic needle is placed nearby, then it will point to the north, and at the same time it will not “feel” an extraneous field, except for the earth's field. And if the charged body begins to move near the arrow, then magnetic field will appear around the body. As a result, it becomes clear that the MF is formed only when a certain charge moves.
• The magnetic field is able to influence and influence the electric current. It can be detected by monitoring the movement of charged electrons. In a magnetic field, particles with a charge will deviate, conductors with a flowing current will move. The current-powered frame will rotate, and the magnetized materials will move a certain distance. The compass needle is most often colored blue. It is a strip of magnetized steel. The compass is always oriented to the north, since the Earth has a magnetic field. The whole planet is like a big magnet with its poles.

The magnetic field is not perceived by human organs, and can only be detected by special devices and sensors. It is variable and permanent. An alternating field is usually created by special inductors that operate on alternating current. A constant field is formed by a constant electric field.

rules

Consider the basic rules for the image of a magnetic field for various conductors.

gimlet rule

The line of force is depicted in a plane, which is located at an angle of 90 0 to the current path so that at each point the force is directed tangentially to the line.

To determine the direction of magnetic forces, you need to remember the rule of a gimlet with a right-hand thread.

The gimlet must be positioned along the same axis as the current vector, the handle must be rotated so that the gimlet moves in the direction of its direction. In this case, the orientation of the lines is determined by turning the handle of the gimlet.

Ring Gimlet Rule

The translational movement of the gimlet in the conductor, made in the form of a ring, shows how the induction is oriented, the rotation coincides with the current flow.

The lines of force have their continuation inside the magnet and cannot be open.

The magnetic field of different sources are summed up with each other. In doing so, they create a common field.

Magnets with the same pole repel each other, while those with different poles attract. The value of the strength of interaction depends on the distance between them. As the poles approach, the force increases.

Magnetic field parameters

• Stream chaining ( Ψ ).
• Magnetic induction vector ( AT).
• Magnetic flux ( F).

The intensity of the magnetic field is calculated by the size of the magnetic induction vector, which depends on the force F, and is formed by the current I through a conductor having a length l: V \u003d F / (I * l).

Magnetic induction is measured in Tesla (Tl), in honor of the scientist who studied the phenomena of magnetism and dealt with their calculation methods. 1 T is equal to the induction of the magnetic flux by the force 1 N on length 1m straight conductor at an angle 90 0 to the direction of the field, with a flowing current of one ampere:

1 T = 1 x H / (A x m).

left hand rule

The rule finds the direction of the magnetic induction vector.

If the palm of the left hand is placed in the field so that the lines of the magnetic field enter the palm from the north pole under 90 0, and 4 fingers are placed along the current, the thumb will show the direction of the magnetic force.

If the conductor is at a different angle, then the force will directly depend on the current and the projection of the conductor onto a plane at a right angle.

The force does not depend on the type of conductor material and its cross section. If there is no conductor, and the charges move in another medium, then the force will not change.

When the direction of the magnetic field vector in one direction of one magnitude, the field is called uniform. Different environments affect the size of the induction vector.

magnetic flux

Magnetic induction passing through a certain area S and limited by this area is a magnetic flux.

If the area has a slope at some angle α to the induction line, the magnetic flux is reduced by the size of the cosine of this angle. Its greatest value is formed when the area is at right angles to the magnetic induction:

F \u003d B * S.

Magnetic flux is measured in a unit such as "weber", which is equal to the flow of induction by the value 1 T by area in 1 m 2.

Flux linkage

This concept is used to create a general value of the magnetic flux, which is created from a certain number of conductors located between the magnetic poles.

When the same current I flows through the winding with the number of turns n, the total magnetic flux formed by all the turns is the flux linkage.

Flux linkage Ψ measured in webers, and is equal to: Ψ = n * F.

Magnetic properties

Permeability determines how much the magnetic field in a particular medium is lower or higher than the field induction in a vacuum. A substance is said to be magnetized if it has its own magnetic field. When a substance is placed in a magnetic field, it becomes magnetized.

Scientists have determined the reason why bodies acquire magnetic properties. According to the hypothesis of scientists, there are electric currents of microscopic magnitude inside substances. An electron has its own magnetic moment, which has a quantum nature, moves along a certain orbit in atoms. It is these small currents that determine the magnetic properties.

If the currents move randomly, then the magnetic fields caused by them are self-compensating. The external field makes the currents ordered, so a magnetic field is formed. This is the magnetization of the substance.

Various substances can be divided according to the properties of interaction with magnetic fields.

They are divided into groups:

Paramagnets- substances that have magnetization properties in the direction of the external field, with a low possibility of magnetism. They have a positive field strength. These substances include ferric chloride, manganese, platinum, etc.
Ferrimagnets- substances with magnetic moments that are unbalanced in direction and value. They are characterized by the presence of uncompensated antiferromagnetism. Field strength and temperature affect their magnetic susceptibility (various oxides).
ferromagnets- substances with increased positive susceptibility, depending on the intensity and temperature (crystals of cobalt, nickel, etc.).
Diamagnets- have the property of magnetization in the opposite direction of the external field, that is, a negative value of magnetic susceptibility, independent of the intensity. In the absence of a field, this substance will not have magnetic properties. These substances include: silver, bismuth, nitrogen, zinc, hydrogen and other substances.
Antiferromagnets - have a balanced magnetic moment, resulting in a low degree of magnetization of the substance. When heated, they undergo a phase transition of the substance, in which paramagnetic properties arise. When the temperature drops below a certain limit, such properties will not appear (chromium, manganese).

The considered magnets are also classified into two more categories:

Soft magnetic materials . They have low coercive force. In weak magnetic fields, they can saturate. During the process of magnetization reversal, they have insignificant losses. As a result, such materials are used for the production of cores of electrical devices operating on alternating voltage (, generator,).
hard magnetic materials. They have an increased value of coercive force. To remagnetize them, a strong magnetic field is required. Such materials are used in the production of permanent magnets.

The magnetic properties of various substances find their use in technical designs and inventions.

Magnetic circuits

The combination of several magnetic substances is called a magnetic circuit. They are similarities and are determined by analogous laws of mathematics.

On the basis of magnetic circuits, electrical devices, inductances, operate. In a functioning electromagnet, the flow flows through a magnetic circuit made of a ferromagnetic material and air, which is not a ferromagnet. The combination of these components is a magnetic circuit. Many electrical devices contain magnetic circuits in their design.

Just as an electric charge at rest acts on another charge through an electric field, an electric current acts on another current through magnetic field. The action of a magnetic field on permanent magnets is reduced to its action on charges moving in the atoms of a substance and creating microscopic circular currents.

Doctrine of electromagnetism based on two assumptions:

• the magnetic field acts on moving charges and currents;
• a magnetic field arises around currents and moving charges.

Interaction of magnets

Permanent magnet(or magnetic needle) is oriented along the magnetic meridian of the Earth. The end pointing north is called north pole(N) and the opposite end is south pole(S). Approaching two magnets to each other, we note that their like poles repel, and opposite ones attract ( rice. one ).

If we separate the poles by cutting the permanent magnet into two parts, then we will find that each of them will also have two poles, i.e. will be a permanent magnet ( rice. 2 ). Both poles - north and south - are inseparable from each other, equal.

The magnetic field created by the Earth or permanent magnets is depicted, like the electric field, by magnetic lines of force. A picture of the magnetic field lines of any magnet can be obtained by placing a sheet of paper over it, on which iron filings are poured in a uniform layer. Getting into a magnetic field, the sawdust is magnetized - each of them has a north and south poles. Opposite poles tend to approach each other, but this is prevented by the friction of sawdust on paper. If you tap the paper with your finger, the friction will decrease and the filings will be attracted to each other, forming chains that represent the lines of a magnetic field.

On the rice. 3 shows the location in the field of a direct magnet of sawdust and small magnetic arrows indicating the direction of the magnetic field lines. For this direction, the direction of the north pole of the magnetic needle is taken.

Oersted's experience. Magnetic field current

At the beginning of the XIX century. Danish scientist Oersted made an important discovery by discovering action of electric current on permanent magnets . He placed a long wire near the magnetic needle. When a current was passed through the wire, the arrow turned, trying to be perpendicular to it ( rice. 4 ). This could be explained by the appearance of a magnetic field around the conductor.

The magnetic lines of force of the field created by a direct conductor with current are concentric circles located in a plane perpendicular to it, with centers at the point through which the current passes ( rice. 5 ). The direction of the lines is determined by the right screw rule:

If the screw is rotated in the direction of the field lines, it will move in the direction of the current in the conductor .

The force characteristic of the magnetic field is magnetic induction vector B . At each point, it is directed tangentially to the field line. Electric field lines start on positive charges and end on negative ones, and the force acting in this field on a charge is directed tangentially to the line at each of its points. Unlike the electric field, the lines of the magnetic field are closed, which is due to the absence of "magnetic charges" in nature.

The magnetic field of the current is fundamentally no different from the field created by a permanent magnet. In this sense, an analogue of a flat magnet is a long solenoid - a coil of wire, the length of which is much greater than its diameter. The diagram of the lines of the magnetic field he created, depicted in rice. 6 , similar to that for a flat magnet ( rice. 3 ). The circles indicate the sections of the wire forming the solenoid winding. The currents flowing through the wire from the observer are indicated by crosses, and the currents in the opposite direction - towards the observer - are indicated by dots. The same designations are accepted for magnetic field lines when they are perpendicular to the plane of the drawing ( rice. 7 a, b).

The direction of the current in the solenoid winding and the direction of the magnetic field lines inside it are also related by the right screw rule, which in this case is formulated as follows:

If you look along the axis of the solenoid, then the current flowing in the clockwise direction creates a magnetic field in it, the direction of which coincides with the direction of movement of the right screw ( rice. eight )

Based on this rule, it is easy to figure out that the solenoid shown in rice. 6 , its right end is the north pole, and its left end is the south pole.

The magnetic field inside the solenoid is homogeneous - the magnetic induction vector has a constant value there (B = const). In this respect, the solenoid is similar to a flat capacitor, inside which a uniform electric field is created.

The force acting in a magnetic field on a conductor with current

It was experimentally established that a force acts on a current-carrying conductor in a magnetic field. In a uniform field, a rectilinear conductor of length l, through which current I flows, located perpendicular to the field vector B, experiences the force: F = I l B .

The direction of the force is determined left hand rule:

If the four outstretched fingers of the left hand are placed in the direction of the current in the conductor, and the palm is perpendicular to the vector B, then the retracted thumb will indicate the direction of the force acting on the conductor (rice. nine ).

It should be noted that the force acting on a conductor with current in a magnetic field is not directed tangentially to its lines of force, like an electric force, but perpendicular to them. A conductor located along the lines of force is not affected by the magnetic force.

The equation F = IlB allows to give a quantitative characteristic of the magnetic field induction.

Attitude does not depend on the properties of the conductor and characterizes the magnetic field itself.

The module of the magnetic induction vector B is numerically equal to the force acting on a conductor of unit length located perpendicular to it, through which a current of one ampere flows.

In the SI system, the unit of magnetic field induction is tesla (T):

A magnetic field. Tables, diagrams, formulas

(Interaction of magnets, Oersted experiment, magnetic induction vector, vector direction, superposition principle. Graphic representation of magnetic fields, magnetic induction lines. Magnetic flux, energy characteristic of the field. Magnetic forces, Ampere force, Lorentz force. Movement of charged particles in a magnetic field. Magnetic properties of matter, Ampère's hypothesis)

For a long time, the magnetic field has raised many questions in humans, but even now it remains a little-known phenomenon. Many scientists tried to study its characteristics and properties, because the benefits and potential of using the field were indisputable facts.

Let's take everything in order. So, how does any magnetic field act and form? That's right, electric current. And the current, according to physics textbooks, is a stream of charged particles with a direction, isn't it? So, when a current passes through any conductor, a certain kind of matter begins to act around it - a magnetic field. The magnetic field can be created by the current of charged particles or by the magnetic moments of electrons in atoms. Now this field and matter have energy, we see it in electromagnetic forces that can affect the current and its charges. The magnetic field begins to act on the flow of charged particles, and they change the initial direction of motion perpendicular to the field itself.

Another magnetic field can be called electrodynamic, because it is formed near moving particles and affects only moving particles. Well, it is dynamic due to the fact that it has a special structure in rotating bions in a region of space. An ordinary electric moving charge can make them rotate and move. Bions transmit any possible interactions in this region of space. Therefore, the moving charge attracts one pole of all bions and causes them to rotate. Only he can bring them out of a state of rest, nothing else, because other forces will not be able to influence them.

In an electric field are charged particles that move very fast and can travel 300,000 km in just a second. Light has the same speed. There is no magnetic field without an electric charge. This means that the particles are incredibly closely related to each other and exist in a common electromagnetic field. That is, if there are any changes in the magnetic field, then there will be changes in the electric field. This law is also reversed.

We talk a lot about the magnetic field here, but how can you imagine it? We cannot see it with our human naked eye. Moreover, due to the incredibly fast propagation of the field, we do not have time to fix it with the help of various devices. But in order to study something, one must have at least some idea of ​​it. It is also often necessary to depict the magnetic field in diagrams. In order to make it easier to understand it, conditional field lines are drawn. Where did they get them from? They were invented for a reason.

Let's try to see the magnetic field with the help of small metal filings and an ordinary magnet. We will pour these sawdust on a flat surface and introduce them into the action of a magnetic field. Then we will see that they will move, rotate and line up in a pattern or pattern. The resulting image will show the approximate effect of forces in a magnetic field. All forces and, accordingly, lines of force are continuous and closed in this place.

The magnetic needle has similar characteristics and properties to a compass and is used to determine the direction of the lines of force. If it falls into the zone of action of a magnetic field, we can see the direction of action of forces by its north pole. Then we will single out several conclusions from here: the top of an ordinary permanent magnet, from which the lines of force emanate, is designated by the north pole of the magnet. Whereas the south pole denotes the point where the forces are closed. Well, the lines of force inside the magnet are not highlighted in the diagram.

The magnetic field, its properties and characteristics are of great use, because in many problems it has to be taken into account and studied. This is the most important phenomenon in the science of physics. More complex things are inextricably linked with it, such as magnetic permeability and induction. To explain all the reasons for the appearance of a magnetic field, one must rely on real scientific facts and confirmations. Otherwise, in more complex problems, the wrong approach can violate the integrity of the theory.

Now let's give examples. We all know our planet. You say that it has no magnetic field? You may be right, but scientists say that the processes and interactions inside the Earth's core create a huge magnetic field that stretches for thousands of kilometers. But any magnetic field must have its poles. And they exist, just located a little away from the geographic pole. How do we feel it? For example, birds have developed navigation abilities, and they orient themselves, in particular, by the magnetic field. So, with his help, the geese arrive safely in Lapland. Special navigation devices also use this phenomenon.