Magnetic fields arise in nature and can be created artificially. The man noticed them useful characteristics, which I learned to apply in Everyday life... What is the source magnetic field?
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Earth's magnetic field
How did the theory of the magnetic field develop
The magnetic properties of some substances were noticed in antiquity, but their real study began in medieval Europe... Using fine steel needles, the French scientist Peregrine discovered the intersection of power magnetic lines at certain points - poles. Only three centuries later, guided by this discovery, Gilbert continued his study and subsequently defended his hypothesis that the Earth has its own magnetic field.
The rapid development of the theory of magnetism began in the early 19th century, when Ampere discovered and described the influence electric field on the emergence of magnetic, and the discovery by Faraday electromagnetic induction established an inverse relationship.
What is magnetic field
A magnetic field manifests itself in a forceful effect on electric charges in motion, or on bodies that have a magnetic moment.
Sources of magnetic field:
- The conductors through which it passes electricity;
- Permanent magnets;
- Changing electric field.
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Sources of magnetic field
The root cause of the appearance of a magnetic field is identical for all sources: electric micro-charges - 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.
Magnetic field characteristics
The characteristics of the magnetic field are:
- Magnetic flux, scalar determining how much power lines the magnetic field passes through a given cross section. It is designated by the letter F. Calculated by the formula:
F = B x S x cos α,
where B is the vector of magnetic induction, S is the section, α is the angle of inclination of the vector to the perpendicular drawn to the plane of the section. Measurement unit - weber (Wb);
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Magnetic flux
- The vector of magnetic induction (B) shows the force acting on the charge carriers. It is directed towards the North Pole, where the usual magnetic needle points. Quantitatively, the magnetic induction is measured in tesla (T);
- Tension MP (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 the magnetic induction. The unit of measurement is A / m.
How to imagine a magnetic field
It is easy to see the manifestation of a magnetic field on 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 in this case:
- 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 that depends on the magnetic force;
- An alternative way to represent it is to use ley lines. These lines never intersect, do not start or stop anywhere, forming closed loops. MF lines merge in more frequent areas where the magnetic field is strongest.
Important! The density of the lines of force indicates the strength of the magnetic field.
Although in reality the MP cannot be seen, the lines of force are easy to visualize in real world by placing iron filings in the MP. Each particle behaves like a tiny magnet with 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: strength and direction. The direction is easy to measure with 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 appeared only in the 19th century. Most of them work by using the force that the electron senses when moving along the MP.
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Magnetometer
Very accurate measurement of low magnetic fields has become feasible since the discovery in 1988 of giant magnetoresistance in layered materials. This discovery in fundamental physics was quickly applied to magnetic technology. hard disk for storing data on computers, which has led to a thousandfold increase in storage capacity in just a few years.
In conventional measurement systems, MF is measured in tests (T) or in gauss (G). 1 T = 10000 G. Gauss is often used because Tesla is too large a field.
Interesting. A small magnet on the refrigerator creates a MF equal to 0.001 T, and the Earth's magnetic field on average is 0.00005 T.
The nature of the occurrence of the magnetic field
Magnetism and magnetic fields are manifestations of electromagnetic force. There are two possible ways how to organize the energy charge in motion and, consequently, the magnetic field.
The first is to connect the wire to a current source, a MF is formed around it.
Important! As the current (the number of charges in motion) increases, the MF increases proportionally. With distance 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 with higher magnetic permeability are capable of concentrating magnetic fields.
Since the magnetic field is a vector, it is necessary to determine its direction. For an ordinary current flowing through a straight wire, the direction can be found by the rule right hand.
To use the rule, one must imagine that the wire is wrapped around the right hand, and thumb indicates the direction of the current. Then the other four 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 electrons with their own magnetic moment appear in some substances. This is how permanent magnets work:
- Although atoms often have many electrons, they generally bond in such a way that the total magnetic field of the pair is canceled out. It is said that two electrons paired in this way 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 in atoms can be randomly oriented, and there will be no total MF, no matter how many unpaired electrons the material has. It must be stable at low temperatures to provide an overall preferred orientation of the electrons. High magnetic permeability determines the magnetization of such substances under certain conditions outside the influence of MF. These are ferromagnets;
- Other materials can exhibit magnetic properties in the presence of an external MF. The external field serves to align all electron spins, which disappears after the removal of the MF. These substances are paramagnets. Refrigerator door metal is an example of a paramagnet.
Earth's magnetic field
The earth can be represented in the form of capacitor plates, the charge of which has opposite sign: "Minus" - at the earth's surface and "plus" - in the ionosphere. Between them is atmospheric air as an insulating pad. 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's transformer, capable of generating high-frequency oscillations and creating a corona discharge, ionizing the air.
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Tesla coil
Tesla's coil will act as an electron emitter. The whole structure is connected together, and the transformer must be raised to a considerable height to ensure a sufficient potential difference. 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 worlds around humans: from the most fundamental processes in nature to cutting edge electronic devices.
Video
On the Internet, there are a lot of topics devoted to the study of the magnetic field. It should be noted that many of them differ from the average description that exists in school textbooks. My task is to collect and organize all available in free access material on the magnetic field in order to focus the New Understanding of the magnetic field. The study of the magnetic field and its properties can be done using a variety of techniques. With the help of iron filings, for example, a competent analysis was carried out by Comrade Fatyanov at http://fatyf.narod.ru/Addition-list.htm
With the help of a picture tube. I do not know the last name of this person, but I know his nickname. He calls himself "Breeze". When the magnet is brought up to the CRT, a "honeycomb pattern" is formed on the screen. You might think that the "grid" is a continuation of the CRT. It is a method of visualizing a magnetic field.
I began to study the magnetic field using a ferromagnetic fluid. It is the magnetic fluid that maximally visualizes all the subtleties of the magnetic field of the magnet.
From the article "what is a magnet" we found out that a magnet is fractalized, i.e. a scaled-down copy of our planet, the magnetic geometry of which is as much as possible identical to a simple magnet. The planet earth, in turn, is a copy of what it was formed from - the sun. We figured out that a magnet is a kind of induction lens that focuses on its volume all the properties of the global magnet of the planet earth. There is a need to introduce new terms with which we will describe the properties of the magnetic field.
An induction flow is a flow that originates at the poles of the planet and passes through us in the geometry of the funnel. The north pole of the planet is the entrance to the funnel, the south pole of the planet is the exit of the funnel. Some scientists call this stream the etheric wind, saying that it is "of galactic origin." But this is not an "etheric wind" and it is not ether, it is an "induction river" that flows from pole to pole. The electricity in lightning is of the same nature as the electricity produced by the interaction of a coil and a magnet.
The best way to understand what a magnetic field is is to see him. It is possible to contemplate and make countless theories, but from the standpoint of understanding the physical essence of the phenomenon, it is useless. I think that everyone will agree with me if I repeat the words I don’t remember who, but the essence is that best criterion this is an experience. Experience and more experience.
At home I did simple experiments, but let me understand a lot. A simple cylindrical magnet ... And so and so he twisted it. I poured magnetic fluid on it. There is an infection, it does not move. Then I remembered that on some forum I read that two magnets squeezed by the same poles in the hermetically sealed area increase the temperature of the area, and, on the contrary, lower the temperature by the opposite poles. If temperature is a consequence of the interaction of fields, then why not be the cause? I heated the magnet using a 12 volt "short" and resistor by simply leaning the heated resistor against the magnet. The magnet warmed up and the magnetic fluid began to twitch at first, and then completely became mobile. The magnetic field is excited by temperature. But how can this be, I asked myself, because the primers write that temperature weakens the magnetic properties of a magnet. And this is true, but this "weakening" of the kagba is compensated by the excitation of the magnetic field of this magnet. In other words, the magnetic force does not disappear, but is transformed by the force of the excitation of this field. Great Everything is spinning and everything is spinning. But why does a rotating magnetic field have just such a geometry of rotation, and not some other? At first glance, the movement is chaotic, but if you look through a microscope, you can see that in this movement there is a system. The system does not belong to the magnet in any way, But only localizes it. In other words, the magnet can be considered as an energetic lens that focuses perturbations in its volume.
The magnetic field is excited not only from an increase in temperature, but also from a decrease in it. I think that it would be more correct to say that the magnetic field is excited by a temperature gradient rather than by some specific sign of it. The fact of the matter is that there is no visible "restructuring" of the structure of the magnetic field. There is a visualization of the disturbance that passes through the region of this magnetic field. Imagine a disturbance spiraling from the North Pole to the South across the entire volume of the planet. So the magnetic field of the magnet = the local part of this global flux. Do you understand? However, I am not sure which particular flow ... But the fact is that the flow. Moreover, there are not one streams, but two. The first is external, and the second is inside it and moves together with the first, but rotates in the opposite direction. The magnetic field is excited due to the temperature gradient. But we again distort the point when we say "the magnetic field is excited." The fact is that it is already in an excited state. When we apply a temperature gradient, we distort this excitation to a state of imbalance. Those. we understand that the excitation process is a constant process in which the magnetic field of the magnet is located. The gradient distorts the parameters of this process so that we optically notice the difference between its normal excitation and the excitation caused by the gradient.
But why is the magnetic field of a magnet stationary in a stationary state? NO, it is also mobile, but relative to moving frames of reference, for example us, it is motionless. We move in space with this indignation of Ra and it seems to us moving. The temperature we apply to the magnet creates a local imbalance in this focusing system. There will be some instability in the spatial grid, which is a honeycomb structure. After all, bees do not build their houses from scratch, but they cling to the structure of space with their building material. Thus, proceeding from purely experimental observations, I conclude that the magnetic field of a simple magnet is a potential system of local imbalance of the lattice of space, in which, as you may have guessed, there is no place for atoms and molecules that no one has ever seen. Temperature is like an "ignition key" in this local system turns on imbalance. I am currently researching methods and controls for this imbalance.
What is a magnetic field and how does it differ from an electromagnetic field?
What is a torsion or energy-informational field?
These are all the same, but localized by different methods.
The strength of the current is a plus and the repulsive force,
tension is a minus and a force of attraction,
a short circuit, or, say, a local imbalance of the lattice, is resistance to this interpenetration. Or the interpenetration of father, son and holy spirit. Remember that the metaphor of "adam and eve" is the old understanding of the x and ygric chromosomes. For understanding the new is a new understanding of the old. "The strength of the current" is a vortex emanating from the constantly rotating Ra, leaving behind itself the informational interweaving of itself. Tension is one more vortex, but inside the main vortex of Ra and moving with it. Visually, this can be represented as a shell, the growth of which occurs in the direction of two spirals. The first is external, the second is internal. Or one inside itself and clockwise, and the second from itself and counterclockwise. When two vortices penetrate each other, they form a structure, like the layers of Jupiter, which move in different sides... It remains to understand the mechanism of this interpenetration and the system that is being formed.
Approximate targets for 2015
1. Find methods and means of imbalance control.
2. Identify the materials most affecting the imbalance of the system. Find the dependence on the state of the material according to table 11 of the child.
3. If every living being, in its essence, is the same localized imbalance, then it must be "seen". In other words, it is necessary to find a method for fixing a person in other frequency spectra.
4. The main task is to visualize non-biological frequency spectra in which the continuous process of human creation takes place. For example, with the help of the means of progress, we analyze the frequency spectra that are not included in the biological spectrum of human senses. But we only register them, but we cannot "realize" them. Therefore, we do not see further than our senses can perceive. This is my main goal for 2015. Find a technique for technical awareness of the non-biological spectrum of frequencies in order to see the informational basis of a person. Those. essentially his soul.
A special kind of study is a magnetic field in motion. If we pour a magnetic fluid onto a magnet, it will occupy the volume of the magnetic field and will be stationary. However, it is necessary to check the experience of "Veterok" where he brought a magnet to the monitor screen. There is an assumption that the magnetic field is already in an excited state, but the volume of the liquid restrains it in a stationary state. But I haven't checked it yet.
The magnetic field can be generated by applying temperature to the magnet, or by placing the magnet in an induction coil. It should be noted that the liquid is excited only at a certain spatial position of the magnet inside the coil, making up a certain angle to the axis of the coil, which can be found empirically.
I conducted dozens of experiments with a moving magnetic fluid and set myself goals:
1. Reveal the geometry of fluid movement.
2. Identify the parameters that affect the geometry of this movement.
3. What is the place of the movement of fluid in the global movement of the planet Earth.
4. Does the spatial position of the magnet and the geometry of motion acquired by it depend.
5. Why tapes?
6. Why do the ribbons curl?
7. What determines the vector of twisting of the ribbons
8. Why the cones are displaced only by means of the nodes, which are the tops of the honeycomb, and only three adjacent ribbons are always twisted.
9. Why does the displacement of the cones occur abruptly, upon reaching a certain "twist" in the nodes?
10. Why is the size of the cones proportional to the volume and mass of the liquid poured onto the magnet?
11. Why is the cone divided into two distinct sectors.
12. What is the place of this "division" in the context of the interaction between the poles of the planet.
13. How the geometry of fluid movement depends on the time of day, season, solar activity, intent of the experimenter, pressure and additional gradients. For example an abrupt change "cold hot"
14. Why the geometry of cones identical with Varji geometry- the special weapons of the returning gods?
15. Are there any data in the archives of the special services of 5 assault rifles any information about the purpose, presence or storage of samples of this type of weapon.
16. What does the gutted storehouse of knowledge of various secret organizations say about these cones and whether the geometry of the cones is connected with the Star of David, the essence of which is the identity of the geometry of the cones. (Freemasons, Juseites, Vaticans, and other uncoordinated entities).
17. Why is there always a leader among the cones? Those. a cone with a "crown" at the top, which "organizes" the movements of the 5,6,7 cones around itself.
cone at the moment of displacement. Jerk. "... only by moving the letter" G "I will reach him" ....
PERMANENT MAGNETIC FIELDS. Sources of permanent magnetic fields (PMF) at workplaces are permanent magnets, electromagnets, high-current direct current systems (direct current transmission lines, electrolyte baths, and other electrical devices). Permanent magnets and electromagnets are widely used in instrumentation, in magnetic washers of cranes and other fixing devices, in magnetic separators, devices for magnetic water treatment, magnetohydrodynamic generators (MHD), nuclear magnetic resonance (NMR) and electronic paramagnetic resonance (EPR) installations. , as well as in physiotherapy practice.
The main physical parameters characterizing the PMF:
2.0 T (short-term exposure to the body);
5.0 T (short-term exposure to hands);
for the population -
0.01 T (continuous exposure).
Control of PMP at workplaces is carried out in the order of preventive and current sanitary supervision by measuring the field strength and magnetic induction (magnetic flux density). Measurements are carried out at permanent workplaces where personnel are likely to be located. In the absence of a permanent workplace within working area several points are selected, located at different distances from the source. When performing manual operations in the area of action of the PMF and when working with magnetized materials (powders) and permanent magnets, when contact with the PMF is limited to a local effect (hands, shoulder girdle), measurements should be taken at the level of the terminal phalanges of the fingers of the hands, the middle of the forearm, the middle shoulder.
Measurements of the magnetic induction of permanent magnets are carried out by direct contact of the sensor of the device with the surface of the magnet. In hygienic practice, devices are used based on the laws of induction, the Hall effect. Fluxmeters (webmeters) or ballistic galvanometers directly measure changes in magnetic flux, which is closed on a calibrated measuring coil; the most commonly used are ballistic galvanometers of the M-197/1 and M-197/2 types, fluxmeters of the M-119 and M-119t types, and teslameters.
Oerstedmeters can be used to measure the intensity of the PMF by the degree of deflection of the magnetized arrow, i.e., by the magnitude of the moment of forces that rotate the arrow at a certain point in space.
Areas of the production area with levels exceeding the remote control should be marked with special warning signs with an additional explanatory inscription “Caution! A magnetic field!". It is necessary to reduce the impact of PMP on workers by choosing a rational mode of work and rest, reducing the time spent in the conditions of PMP, determining a route that limits contact with PMP in the working area.
Prevention of exposure to PMP. When conducting renovation works busbar systems should be bridged. Persons serving technological installations direct current, busbar systems or those in contact with PMP sources, must pass preliminary and periodic in the prescribed manner.
In the electronics industry when assembling semiconductor devices use end-to-end technological cassettes that limit the contact of the hands with the PMP. At enterprises for the production of permanent magnets, the process of measuring the magnetic parameters of products is automated by means of devices that exclude contact with PMF. It is advisable to use remote devices (forceps made of non-magnetic materials, tweezers, grips), which prevent the possibility of local action of the PMP on the worker. Interlocking devices must be used to disconnect electromagnetic installation when hands get into the zone of action of the PMP.
To understand what is a characteristic of a magnetic field, it is necessary to give definitions to many phenomena. In this case, you need to remember in advance how and why it appears. Find out what is the strength characteristic of a magnetic field. At the same time, it is important that such a field can occur not only in magnets. In this regard, it does not hurt to mention the characteristics of the earth's magnetic field.
Field emergence
First, you should describe the occurrence of the field. Then you can describe the magnetic field and its characteristics. It appears during the movement of charged particles. May affect, in particular, conductive conductors. The interaction between a magnetic field and moving charges, or conductors through which current flows, occurs due to forces called electromagnetic.
The intensity or force characteristic of a magnetic field at a certain spatial point is determined using magnetic induction. The latter is indicated by the symbol B.
Graphical representation of the field
The magnetic field and its characteristics can be represented graphically using induction lines. This definition is called lines, tangents to which at any point will coincide with the direction of the vector of the magnetic induction.
The named lines are included in the characteristics of the magnetic field and are used to determine its direction and intensity. The higher the intensity of the magnetic field, the more of these lines will be drawn.
What are magnetic lines
Magnetic lines in straight conductors with current have the shape of a concentric circle, the center of which is located on the axis of this conductor. The direction of the magnetic lines near the conductors with current is determined by the gimbal's rule, which sounds like this: if the gimbal is positioned so that it is screwed into the conductor in the direction of the current, then the direction of rotation of the handle corresponds to the direction of the magnetic lines.
For a coil with a current, the direction of the magnetic field will also be determined by the gimbal's rule. It is also required to rotate the handle in the direction of the current in the turns of the solenoid. The direction of the lines of magnetic induction will correspond to the direction of the translational movement of the gimbal.
It is the main characteristic of the magnetic field.
Created by one current, at equal conditions, the field will differ in its intensity in different environments due to different magnetic properties in these substances. The magnetic properties of the medium are characterized by absolute magnetic permeability. Measured in henry per meter (g / m).
The characteristic of the magnetic field includes the absolute magnetic permeability of the vacuum, called the magnetic constant. The value that determines how many times the absolute magnetic permeability of the medium will differ from the constant is called the relative magnetic permeability.
Magnetic permeability of substances
This is a dimensionless quantity. Substances with a permeability value of less than one are called diamagnetic. In these substances, the field will be weaker than in a vacuum. These properties are present in hydrogen, water, quartz, silver, etc.
Media with a magnetic permeability exceeding unity are called paramagnetic. In these substances, the field will be stronger than in a vacuum. These media and substances include air, aluminum, oxygen, platinum.
In the case of paramagnetic and diamagnetic substances, the value of the magnetic permeability will not depend on the voltage of the external, magnetizing field. This means that the value is constant for a particular substance.
Ferromagnets belong to a special group. For these substances, the magnetic permeability will reach several thousand or more. These substances, which have the property of magnetizing and strengthening the magnetic field, are widely used in electrical engineering.
Field strength
To determine the characteristics of the magnetic field, a value called the magnetic field strength can be used in conjunction with the magnetic induction vector. This term is defining the intensity of the external magnetic field. The direction of the magnetic field in a medium with the same properties in all directions, the intensity vector will coincide with the vector of magnetic induction at the point of the field.
The strong ones in ferromagnets are explained by the presence of arbitrarily magnetized small parts in them, which can be represented in the form of small magnets.
With the absence of a magnetic field, a ferromagnetic substance may not have pronounced magnetic properties, since the fields of the domains acquire different orientations, and their total magnetic field is equal to zero.
According to the main characteristics of the magnetic field, if a ferromagnet is placed in an external magnetic field, for example, in a coil with a current, then under the influence of the external field, the domains will unfold in the direction of the external field. Moreover, the magnetic field at the coil will increase, and the magnetic induction will increase. If the external field is weak enough, then only a part of all domains will turn over, the magnetic fields of which are close to the direction of the external field. As the strength of the external field increases, the number of rotated domains will increase, and at a certain value of the external field voltage, almost all parts will be rotated so that the magnetic fields are located in the direction of the external field. This state is called magnetic saturation.
Relationship between magnetic induction and tension
The relationship between the magnetic induction of a ferromagnetic substance and the strength of the external field can be depicted using a graph called the magnetization curve. At the bend in the curve, the rate of increase in magnetic induction decreases. After a bend, where the tension reaches a certain value, saturation occurs, and the curve rises slightly, gradually acquiring the shape of a straight line. In this section, the induction is still growing, but rather slowly and only due to an increase in the strength of the external field.
The graphical dependence of these indicators is not direct, which means that their ratio is not constant, and the magnetic permeability of the material is not a constant indicator, but depends on the external field.
Changes in the magnetic properties of materials
With an increase in the current strength to full saturation in a coil with a ferromagnetic core and its subsequent decrease, the magnetization curve will not coincide with the demagnetization curve. With zero intensity, the magnetic induction will not have the same value, but will acquire a certain indicator called the residual magnetic induction. The situation with the lag of the magnetic induction from the magnetizing force is called hysteresis.
To completely demagnetize the ferromagnetic core in the coil, it is required to give a reverse directional current, which will create the necessary tension. For different ferromagnetic substances, a section of different lengths is required. The larger it is, the more energy is required for demagnetization. The value at which the material is completely demagnetized is called the coercive force.
With a further increase in the current in the coil, the induction will again increase to the saturation index, but with a different direction of the magnetic lines. When demagnetizing in the opposite direction, a residual induction will be obtained. The phenomenon of residual magnetism is used to create permanent magnets from substances with a high index of residual magnetism. From substances that have the ability to magnetize, cores are created for electric cars and appliances.
Left hand rule
The force affecting the conductor with current has a direction determined by the rule of the left hand: when the palm of the virgin hand is positioned in such a way that the magnetic lines enter it, and four fingers are extended in the direction of the current in the conductor, the bent thumb will indicate the direction of the force. This force is perpendicular to the induction vector and current.
A conductor with a current moving in a magnetic field is considered a prototype of an electric motor, which changes electrical energy into mechanical.
Right hand rule
During the movement of the conductor in a magnetic field, an electromotive force is induced inside it, which has a value proportional to the magnetic induction, the length of the conductor involved and the speed of its movement. This dependence is called electromagnetic induction. When determining the direction of the induced EMF in the conductor, the rule of the right hand is used: when the right hand is positioned in the same way as in the example with the left, the magnetic lines enter the palm, and the thumb indicates the direction of movement of the conductor, extended fingers indicate the direction of the induced EMF. A conductor moving in a magnetic flux under the influence of an external mechanical force is the simplest example electric generator, in which mechanical energy is converted into electrical energy.
It can be formulated differently: in a closed loop, an EMF is induced; for any change in the magnetic flux covered by this loop, the EDF in the loop is numerically equal to the rate of change of the magnetic flux that covers this loop.
This form provides an average EMF indicator and indicates the dependence of the EMF not on the magnetic flux, but on the rate of its change.
Lenz's law
You also need to remember Lenz's law: the current induced by a change in the magnetic field passing through the circuit, by its magnetic field, prevents this change. If the turns of the coil are penetrated by magnetic fluxes of different magnitude, then the EMF induced over the whole coil is equal to the sum of EDU in different turns. The sum of the magnetic fluxes of different turns of the coil is called flux linkage. The unit of measurement of this quantity, like the magnetic flux, is weber.
When the electric current in the circuit changes, the magnetic flux created by it also changes. In this case, according to the law of electromagnetic induction, EMF is induced inside the conductor. It appears in connection with a change in the current in the conductor, therefore this phenomenon is called self-induction, and the EMF induced in the conductor is called the self-induction EMF.
Flux linkage and magnetic flux are dependent not only on the strength of the current, but also on the size and shape of the given conductor, and the magnetic permeability of the surrounding substance.
Conductor inductance
The proportionality factor is called the conductor inductance. It denotes the ability of a conductor to create flux linkage when electricity passes through it. This is one of the main parameters of electrical circuits. For certain circuits, inductance is a constant value. It will depend on the size of the circuit, its configuration and the magnetic permeability of the medium. In this case, the current in the circuit and the magnetic flux will not matter.
The above definitions and phenomena provide an explanation for what a magnetic field is. The main characteristics of the magnetic field are also given, with the help of which it is possible to define this phenomenon.
Magnetic field and its characteristics. When an electric current passes through a conductor, a a magnetic field. A magnetic field represents one of the types of matter. It has energy that manifests itself in the form electromagnetic forces acting on separate moving electric charges (electrons and ions) and on their flows, i.e. electric current. Under the influence of electromagnetic forces, moving charged particles deviate from their original path in a direction perpendicular to the field (Fig. 34). The magnetic field is formed only around moving electric charges, and its action also extends only to moving charges. Magnetic and electric fields inseparable and together form a single electromagnetic field... Every change electric field leads to the appearance of a magnetic field and, conversely, any change in the magnetic field is accompanied by the appearance of an electric field. Electromagnetic field propagates at the speed of light, that is, 300,000 km / s.
Graphical representation of the magnetic field. Graphically, the magnetic field is depicted by magnetic lines of force, which are drawn so that the direction of the line of force at each point of the field coincides with the direction of the field forces; magnetic lines of force are always continuous and closed. The direction of the magnetic field at each point can be determined using the magnetic arrow. The north pole of the arrow is always set in the direction of the field forces. The end of the permanent magnet, from which the lines of force come out (Fig. 35, a), is considered to be the north pole, and the opposite end, into which the lines of force enter, is the south pole (the lines of force passing inside the magnet are not shown). The distribution of lines of force between the poles of a flat magnet can be detected using steel filings poured onto a sheet of paper placed on the poles (Fig. 35, b). The magnetic field in the air gap between two parallel opposite poles of a permanent magnet is characterized by a uniform distribution of magnetic lines of force (Fig. 36) (lines of force passing inside the magnet are not shown).
Rice. 37. Magnetic flux penetrating the coil at perpendicular (a) and oblique (b) positions with respect to the direction of the magnetic field lines.
For a more visual representation of the magnetic field, the lines of force are placed less frequently or denser. In those places where the magnetic role is stronger, the lines of force are placed closer to each other, in the same places where it is weaker - farther from each other. The lines of force do not intersect anywhere.
In many cases, it is convenient to consider magnetic lines of force as some elastic stretched filaments that tend to contract, and also mutually repel each other (have a mutual lateral thrust). Such a mechanical representation of lines of force allows you to visually explain the occurrence of electromagnetic forces during the interaction of a magnetic field and a Conductor with current, as well as two magnetic fields.
The main characteristics of a magnetic field are magnetic induction, magnetic flux, permeability and magnetic field strength.
Magnetic induction and magnetic flux. The intensity of the magnetic field, that is, its ability to perform work, is determined by a quantity called magnetic induction. The stronger the magnetic field created permanent magnet or an electromagnet, the greater the induction it has. Magnetic induction B can be characterized by the density of magnetic lines of force, that is, the number of lines of force passing through an area of 1 m 2 or 1 cm 2, located perpendicular to the magnetic field. Distinguish between homogeneous and non-uniform magnetic fields. In a uniform magnetic field, the magnetic induction at each point of the field has the same value and direction. The field in the air gap between opposite poles of a magnet or electromagnet (see Figure 36) at some distance from its edges can be considered uniform. The magnetic flux Ф passing through any surface is determined by the total number of magnetic lines of force penetrating this surface, for example, coil 1 (Fig. 37, a), therefore, in a uniform magnetic field
Ф = BS (40)
where S is the cross-sectional area of the surface through which the magnetic lines of force pass. It follows that in such a field, the magnetic induction is equal to the flux divided by the cross-sectional area S:
B = F/ S (41)
If any surface is located obliquely with respect to the direction of the magnetic lines of force (Fig. 37, b), then the flux penetrating it will be less than when it is perpendicular to it, that is, Ф 2 will be less than Ф 1.
In the SI system of units, the magnetic flux is measured in Weber (Wb), this unit has the dimension B * s (volt-second). Magnetic induction in SI units is measured in tesla (T); 1 T = 1 Wb / m 2.
Magnetic permeability. Magnetic induction depends not only on the strength of the current passing through a straight conductor or coil, but also on the properties of the medium in which the magnetic field is created. The quantity characterizing the magnetic properties of the medium is the absolute magnetic permeability? a. Its unit of measurement is henry per meter (1 H / m = 1 Ohm * s / m).
In a medium with a higher magnetic permeability, an electric current of a certain strength creates a magnetic field with a higher induction. It has been established that the magnetic permeability of air and all substances, with the exception of ferromagnetic materials (see § 18), has approximately the same value - as the magnetic permeability of vacuum. The absolute magnetic permeability of the vacuum is called the magnetic constant,? o = 4? * 10 -7 H / m. The magnetic permeability of ferromagnetic materials is thousands and even tens of thousands of times greater than the magnetic permeability of non-ferromagnetic substances. Permeability ratio? and any substance to the magnetic permeability of the vacuum? o is called the relative magnetic permeability:
? =? a /? O (42)
Magnetic field strength. The intensity And does not depend on the magnetic properties of the medium, but takes into account the influence of the current strength and the shape of the conductors on the intensity of the magnetic field at a given point in space. Magnetic induction and tension are related
H = B /? a = B / (?? o) (43)
Consequently, in a medium with constant magnetic permeability, the induction of the magnetic field is proportional to its strength.
Magnetic field strength is measured in amperes per meter (A / m) or amperes per centimeter (A / cm).