In the last century, various scientists put forward several assumptions about the Earth's magnetic field. According to one of them, the field appears as a result of the rotation of the planet around its axis.

It is based on the curious Barnett-Einstein effect, which is that when any body rotates, a magnetic field arises. Atoms in this effect have their own magnetic moment as they rotate around their axis. This is how the Earth's magnetic field appears. However, this hypothesis did not stand up to experimental testing. It turned out that the magnetic field obtained in such a non-trivial way is several million times weaker than the real one.

Another hypothesis is based on the appearance of a magnetic field due to the circular motion of charged particles (electrons) on the surface of the planet. She also turned out to be insolvent. The movement of electrons can cause the appearance of a very weak field, and this hypothesis does not explain the inversion of the Earth's magnetic field. It is known that the north magnetic pole does not coincide with the north geographic pole.

Solar wind and mantle currents

The mechanism of formation of the magnetic field of the Earth and other planets of the solar system has not been fully studied and still remains a mystery to scientists. However, one proposed hypothesis explains the inversion and the magnitude of the real field induction quite well. It is based on the work of the internal currents of the Earth and the solar wind.

The Earth's internal currents flow in the mantle, which consists of substances with very good conductivity. The source of current is the core. Energy from the core to the surface of the earth is transferred by convection. Thus, in the mantle there is a constant movement of matter, which forms a magnetic field according to the well-known law of motion of charged particles. If we associate its appearance only with internal currents, it turns out that all planets whose direction of rotation coincides with the direction of rotation of the Earth should have an identical magnetic field. However, it is not. Jupiter's north geographic pole coincides with its north magnetic pole.

Not only internal currents participate in the formation of the Earth's magnetic field. It has long been known that it responds to the solar wind, a stream of high-energy particles coming from the Sun as a result of reactions occurring on its surface.

The solar wind is, by its nature, an electric current (the movement of charged particles). Carried away by the rotation of the Earth, it creates a circular current, which leads to the appearance of the Earth's magnetic field.

Good day, today you will find out what is a magnetic field and where it comes from.

Every person on the planet has held at least once magnet in hand. Starting from souvenir refrigerator magnets, or working magnets for collecting iron pollen and much more. As a child, it was a funny toy that stuck to ferrous metal, but not to other metals. So what is the secret of the magnet and its magnetic field.

What is a magnetic field

At what point does a magnet begin to attract? Around each magnet there is a magnetic field, entering which objects begin to be attracted to it. The size of such a field can vary depending on the size of the magnet and its own properties.

Wikipedia term:

Magnetic field is a force field acting on moving electric charges and on bodies with a magnetic moment, regardless of the state of their motion, the magnetic component of the electromagnetic field.

Where does the magnetic field come from?

A magnetic field can be created by the current of charged particles or the magnetic moments of electrons in atoms, as well as the magnetic moments of other particles, although to a noticeably lesser extent.

Manifestation of magnetic field

The magnetic field manifests itself in the effect on the magnetic moments of particles and bodies, on moving charged particles or conductors with. The force acting on an electrically charged particle moving in a magnetic field is called the Lorentz force, which is always directed perpendicular to the vectors v and B. It is proportional to the charge of the particle q, the velocity component v perpendicular to the direction of the magnetic field vector B, and the magnitude of the magnetic field induction B.

What objects have a magnetic field

We often don't think about it, but many (if not all) objects around us are magnets. We are accustomed to the fact that a magnet is a pebble with a pronounced force of attraction towards itself, but in fact, almost everything has a force of attraction, it’s just much lower. Let’s take our planet, for example - we don’t fly into space, although we don’t hold onto the surface with anything. The Earth's field is much weaker than the field of a pebble magnet, so it holds us only due to its enormous size - if you have ever seen how people walk on the Moon (the diameter of which is four times smaller), you will clearly understand what we are talking about . The Earth's gravity is based largely on the metallic components of its crust and core - they have a powerful magnetic field. You may have heard that near large deposits of iron ore, compasses no longer point correctly to the north - this is because the principle of the compass is based on the interaction of magnetic fields, and the iron ore attracts its needle.

What are magnetic fields essentially? Changes in the magnetic properties of materials

Magnetic fields occur in nature and can be created artificially. The person noticed their useful characteristics, which he learned to apply in everyday life. What is the source of the magnetic field?

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Earth's magnetic field

How the doctrine of the magnetic field developed

The magnetic properties of some substances were noticed in ancient times, but their study really began in medieval Europe. Using small steel needles, a scientist from France, Peregrine, discovered the intersection of magnetic force lines at certain points - the poles. Only three centuries later, guided by this discovery, Gilbert continued to study it and subsequently defended his hypothesis that the Earth has its own magnetic field.

The rapid development of the theory of magnetism began at the beginning of the 19th century, when Ampere discovered and described the influence of the electric field on the emergence of a magnetic field, and Faraday’s discovery of electromagnetic induction established an inverse relationship.

What is a magnetic field

A magnetic field manifests itself in a force effect on electric charges that are in motion, or on bodies that have a magnetic moment.

Magnetic field sources:

Conductors through which electric current passes;
Permanent magnets;
Changing electric field.

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Magnetic field sources

The root cause of the appearance of a magnetic field is identical for all sources: electrical microcharges - electrons, ions or protons - have their own magnetic moment or are in directional motion.

Important! Electric and magnetic fields mutually generate each other, changing over time. This relationship is determined by Maxwell's equations.

Characteristics of the magnetic field

The characteristics of the magnetic field are:

Magnetic flux, a scalar quantity that determines how many magnetic field lines pass through a given cross section. Denoted by the letter F. Calculated using the formula:

F = B x S x cos α,

where B is the magnetic induction vector, S is the section, α is the angle of inclination of the vector to the perpendicular drawn to the section plane. Unit of measurement – weber (Wb);

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Magnetic flux

The magnetic induction vector (B) shows the force acting on the charge carriers. It is directed towards the north pole, where the usual magnetic needle points. Magnetic induction is measured quantitatively in Tesla (T);
MF tension (N). Determined by the magnetic permeability of various media. In a vacuum, permeability is taken as unity. The direction of the tension vector coincides with the direction of magnetic induction. Unit of measurement – A/m.

How to represent a magnetic field

It is easy to see the manifestations of a magnetic field using the example of a permanent magnet. It has two poles and depending on the orientation the two magnets attract or repel. The magnetic field characterizes the processes occurring during this:

The MP is mathematically described as a vector field. It can be constructed by means of many vectors of magnetic induction B, each of which is directed towards the north pole of the compass needle and has a length depending on the magnetic force;
An alternative way of representing this is to use field lines. These lines never intersect, do not start or stop anywhere, forming closed loops. The MF lines are combined into areas with a more frequent location, where the magnetic field is the strongest.

Important! The density of the field lines indicates the strength of the magnetic field.

Although the MP cannot be seen in reality, the field lines can be easily visualized in the real world by placing iron filings in the MP. Each particle behaves like a tiny magnet with a north and south pole. The result is a pattern similar to lines of force. A person is not able to feel the impact of MP.

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Magnetic field lines

Magnetic field measurement

Since this is a vector quantity, there are two parameters for measuring MF: force and direction. The direction can be easily measured using a compass connected to the field. An example is a compass placed in the Earth's magnetic field.

Measuring other characteristics is much more difficult. Practical magnetometers did not appear until the 19th century. Most of them work by using the force that the electron feels as it moves along the MP.

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Magnetometer

Very precise measurement of small magnetic fields has become practically feasible since the discovery in 1988 of giant magnetoresistance in layered materials. This discovery in fundamental physics was quickly applied to magnetic hard drive technology for data storage in computers, leading to a thousandfold increase in storage capacity in just a few years.

In generally accepted measurement systems, MP is measured in tests (T) or gauss (G). 1 T = 10000 Gs. Gauss is often used because Tesla is too large a field.

Interesting. A small magnet on a refrigerator creates a magnetic field equal to 0.001 Tesla, and the Earth's magnetic field on average is 0.00005 Tesla.

The nature of the magnetic field

Magnetism and magnetic fields are manifestations of electromagnetic force. There are two possible ways to organize an energy charge in motion and, therefore, a magnetic field.

The first is to connect the wire to a current source, an MF is formed around it.

Important! As the current (the number of charges in motion) increases, the MP increases proportionally. As you move away from the wire, the field decreases depending on the distance. This is described by Ampere's law.

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Ampere's law

Some materials that have higher magnetic permeability are capable of concentrating magnetic fields.

Since the magnetic field is a vector, it is necessary to determine its direction. For ordinary current flowing through a straight wire, the direction can be found using the right hand rule.

To use the rule, you need to imagine that the wire is grasped with your right hand, and your thumb indicates the direction of the current. Then the four remaining fingers will show the direction of the magnetic induction vector around the conductor.

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Right hand rule

The second way to create a magnetic field is to use the fact that in some substances electrons appear that have their own magnetic moment. This is how permanent magnets work:

Although atoms often have many electrons, they mostly bond so that the total magnetic field of the pair cancels out. Two electrons paired in this way are said to have opposite spin. Therefore, in order to magnetize something, you need atoms that have one or more electrons with the same spin. For example, iron has four such electrons and is suitable for making magnets;
The billions of electrons found in atoms can be randomly oriented, and there will be no overall MF, no matter how many unpaired electrons the material has. It must be stable at low temperatures to provide an overall preferred orientation of electrons. High magnetic permeability causes the magnetization of such substances under certain conditions outside the influence of magnetic fields. These are ferromagnetic;
Other materials may exhibit magnetic properties in the presence of an external magnetic field. The external field serves to align all electron spins, which disappears after the MF is removed. These substances are paramagnetic. The metal of a refrigerator door is an example of a paramagnetic material.

Earth's magnetic field

The earth can be represented in the form of capacitor plates, the charge of which has the opposite sign: “minus” at the earth’s surface and “plus” in the ionosphere. Between them there is atmospheric air as an insulating spacer. The giant capacitor maintains a constant charge due to the influence of the earth's MF. Using this knowledge, you can create a scheme for obtaining electrical energy from the Earth's magnetic field. True, the result will be low voltage values.

Have to take:

grounding device;
the wire;
Tesla transformer capable of generating high-frequency oscillations and creating a corona discharge, ionizing the air.

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Tesla Coil

The Tesla coil will act as an electron emitter. The entire structure is connected together, and to ensure a sufficient potential difference, the transformer must be raised to a considerable height. Thus, an electrical circuit will be created through which a small current will flow. It is impossible to obtain a large amount of electricity using this device.

Electricity and magnetism dominate many of the worlds around us, from the most fundamental processes in nature to cutting-edge electronic devices.

Video

The term “magnetic field” usually means a certain energy space in which the forces of magnetic interaction manifest themselves. They affect:

individual substances: ferrimagnets (metals - mainly cast iron, iron and their alloys) and their class of ferrites, regardless of state;

moving charges of electricity.

Physical bodies that have a total magnetic moment of electrons or other particles are called permanent magnets. Their interaction is shown in the picture magnetic force lines.

They were formed after bringing a permanent magnet to the back of a cardboard sheet with an even layer of iron filings. The picture shows clear markings of the north (N) and south (S) poles with the direction of the field lines relative to their orientation: exit from the north pole and entrance to the south.

How is a magnetic field created?

The sources of the magnetic field are:

permanent magnets;

moving charges;

time-varying electric field.

Every kindergarten child is familiar with the action of permanent magnets. After all, he already had to sculpt pictures of magnets on the refrigerator, taken from packages with all sorts of delicacies.

Electric charges in motion usually have significantly greater magnetic field energy than . It is also designated by lines of force. Let's look at the rules for drawing them for a straight conductor with current I.

The magnetic field line is drawn in a plane perpendicular to the movement of the current so that at each point the force acting on the north pole of the magnetic needle is directed tangentially to this line. This creates concentric circles around the moving charge.

The direction of these forces is determined by the well-known rule of a screw or gimlet with right-hand thread winding.

Gimlet rule

It is necessary to position the gimlet coaxially with the current vector and rotate the handle so that the translational movement of the gimlet coincides with its direction. Then the orientation of the magnetic field lines will be shown by rotating the handle.

In a ring conductor, the rotational movement of the handle coincides with the direction of the current, and the translational movement indicates the orientation of the induction.

Magnetic lines of force always leave the north pole and enter the south pole. They continue inside the magnet and are never open.

Rules for the interaction of magnetic fields

Magnetic fields from different sources add to each other to form a resulting field.

In this case, magnets with opposite poles (N - S) attract each other, and with like poles (N - N, S - S) they repel. The interaction forces between the poles depend on the distance between them. The closer the poles are shifted, the greater the force generated.

Basic characteristics of the magnetic field

These include:

magnetic induction vector (B);

magnetic flux (F);

flux linkage (Ψ).

The intensity or strength of the field impact is estimated by the value magnetic induction vector. It is determined by the value of the force “F” created by the passing current “I” through a conductor of length “l”. В =F/(I∙l)

The unit of measurement of magnetic induction in the SI system is Tesla (in memory of the physicist who studied these phenomena and described them using mathematical methods). In Russian technical literature it is designated “Tl”, and in international documentation the symbol “T” is adopted.

1 T is the induction of such a uniform magnetic flux, which acts with a force of 1 newton for each meter of length of a straight conductor perpendicular to the direction of the field, when a current of 1 ampere passes through this conductor.

1T=1∙N/(A∙m)

The direction of vector B is determined by left hand rule.

If you place the palm of your left hand in a magnetic field so that the lines of force from the north pole enter the palm at a right angle, and place four fingers in the direction of the current in the conductor, then the protruding thumb will indicate the direction of the force on this conductor.

In the case when the conductor with electric current is not located at right angles to the magnetic lines of force, the force acting on it will be proportional to the magnitude of the flowing current and the component of the projection of the length of the conductor with current onto a plane located in the perpendicular direction.

The force acting on an electric current does not depend on the materials from which the conductor is made and its cross-sectional area. Even if this conductor does not exist at all, and moving charges begin to move in another medium between the magnetic poles, then this force will not change in any way.

If inside a magnetic field at all points the vector B has the same direction and magnitude, then such a field is considered uniform.

Any environment that has , affects the value of the induction vector B .

Magnetic flux (F)

If we consider the passage of magnetic induction through a certain area S, then the induction limited by its limits will be called magnetic flux.

When the area is inclined at some angle α to the direction of magnetic induction, the magnetic flux decreases by the amount of the cosine of the angle of inclination of the area. Its maximum value is created when the area is perpendicular to its penetrating induction. Ф=В·S

The unit of measurement for magnetic flux is 1 weber, defined by the passage of induction of 1 tesla through an area of 1 square meter.

Flux linkage

This term is used to obtain the total amount of magnetic flux created from a certain number of current-carrying conductors located between the poles of a magnet.

For the case when the same current I passes through the winding of a coil with a number of turns n, then the total (linked) magnetic flux from all turns is called flux linkage Ψ.

Ψ=n·Ф . The unit of flux linkage is 1 weber.

How is a magnetic field formed from an alternating electric

The electromagnetic field, interacting with electric charges and bodies with magnetic moments, is a combination of two fields:

electrical;

magnetic.

They are interconnected, represent a combination of each other, and when one changes over time, certain deviations occur in the other. For example, when an alternating sinusoidal electric field is created in a three-phase generator, the same magnetic field with the characteristics of similar alternating harmonics is simultaneously formed.

Magnetic properties of substances

In relation to interaction with an external magnetic field, substances are divided into:

antiferromagnets with balanced magnetic moments, due to which a very low degree of magnetization of the body is created;

Diamagnets with the property of magnetizing an internal field against the action of an external one. When there is no external field, their magnetic properties do not appear;

paramagnetic materials with magnetizing properties of the internal field in the direction of the external field, which have a low degree;

ferromagnets, which have magnetic properties without an applied external field at temperatures below the Curie point;

ferrimagnets with magnetic moments unbalanced in magnitude and direction.

All these properties of substances have found various applications in modern technology.

Magnetic circuits

All transformers, inductors, electrical machines and many other devices operate on this basis.

For example, in a working electromagnet, the magnetic flux passes through a magnetic core made of ferromagnetic steel and air with pronounced non-ferromagnetic properties. The combination of these elements makes up a magnetic circuit.

Most electrical devices have magnetic circuits in their design. Read more about this in this article -

A MAGNETIC FIELD

A magnetic field is a special type of matter, invisible and intangible to humans,
existing independently of our consciousness.
Even in ancient times, scientific thinkers guessed that something existed around a magnet.

Magnetic needle.

A magnetic needle is a device necessary when studying the magnetic action of electric current.
It is a small magnet mounted on the tip of a needle and has two poles: north and south. The magnetic needle can rotate freely on the tip of the needle.
The northern end of the magnetic needle always points to "north".
The line connecting the poles of the magnetic needle is called the axis of the magnetic needle.
A similar magnetic needle is found in any compass - a device for orienting oneself.

Where does the magnetic field originate?

Oersted's experiment (1820) - shows how a conductor with current interacts with a magnetic needle.

When the electrical circuit is closed, the magnetic needle deviates from its original position; when the circuit is opened, the magnetic needle returns to its original position.

A magnetic field arises in the space around a conductor carrying current (and in the general case around any moving electric charge).
The magnetic forces of this field act on the needle and turn it.

In general, we can say
that a magnetic field arises around moving electric charges.
Electric current and magnetic field are inseparable from each other.

IT'S INTERESTING THAT...

Many celestial bodies - planets and stars - have their own magnetic fields.
However, our closest neighbors - the Moon, Venus and Mars - do not have a magnetic field,
similar to earthly.
___

Gilbert discovered that when a piece of iron is brought closer to one pole of a magnet, the other pole begins to attract more strongly. This idea was patented only 250 years after Gilbert's death.

In the first half of the 90s, when new Georgian coins appeared - lari,
local pickpockets have acquired magnets,
because the metal from which these coins were made was well attracted by a magnet!

If you take a dollar bill by the corner and hold it near a powerful magnet
(for example, horseshoe-shaped), creating a non-uniform magnetic field, piece of paper
will deviate towards one of the poles. It turns out that the ink on the dollar bill contains iron salts.
possessing magnetic properties, so the dollar is attracted to one of the poles of the magnet.

If you hold a large magnet close to a carpenter's bubble level, the bubble will move.
The fact is that the bubble level is filled with diamagnetic fluid. When such a liquid is placed in a magnetic field, a magnetic field in the opposite direction is created inside it, and it is pushed out of the field. Therefore, the bubble in the liquid approaches the magnet.

YOU NEED TO KNOW ABOUT THEM!

The organizer of the magnetic compass business in the Russian Navy was a famous deviator scientist,
captain of the 1st rank, author of scientific works on the theory of the compass I.P. Belavanets.
Participant in the round-the-world voyage on the frigate "Pallada" and participant in the Crimean War of 1853-56. He was the first in the world to demagnetize a ship (1863)
and solved the problem of installing compasses inside an iron submarine.
In 1865 he was appointed head of the country's first Compass Observatory in Kronstadt.