To understand what is a characteristic of a magnetic field, many phenomena should be defined. At the same time, you need to remember in advance how and why it appears. Find out what is the power characteristic of a magnetic field. It is also 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.
Emergence of the field
To begin with, it is necessary to describe the appearance of the field. After that, you can describe the magnetic field and its characteristics. It appears during the movement of charged particles. Can affect especially 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 power characteristic of the magnetic field at a certain spatial point is determined using magnetic induction. The latter is denoted 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, the tangents to which at any point will coincide with the direction of the vector y of the magnetic induction.
These 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 data lines will be drawn.
What are magnetic lines
The magnetic lines of 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 rule of the gimlet, which sounds like this: if the gimlet is located so that it will be 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 current, the direction of the magnetic field will also be determined by the gimlet 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 gimlet.
It is the main characteristic of the magnetic field.
Created by one current, under equal conditions, the field will differ in its intensity in different media due to the different magnetic properties in these substances. The magnetic properties of the medium are characterized by absolute magnetic permeability. It is measured in henries 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 vacuum. These properties are present in hydrogen, water, quartz, silver, etc.
Media with a magnetic permeability greater than unity are called paramagnetic. In these substances, the field will be stronger than in vacuum. These media and substances include air, aluminum, oxygen, platinum.
In the case of paramagnetic and diamagnetic substances, the value of 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 being magnetized and amplifying the magnetic field, are widely used in electrical engineering.
Field strength
To determine the characteristics of the magnetic field, together with the magnetic induction vector, a value called the magnetic field strength can be used. This term defines 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 magnetic induction vector at the field point.
The strengths of ferromagnets are explained by the presence in them of arbitrarily magnetized small parts, which can be represented as small magnets.
In the absence of a magnetic field, a ferromagnetic substance may not have pronounced magnetic properties, since the domain fields acquire different orientations, and their total magnetic field is zero.
According to the main characteristic of the magnetic field, if a ferromagnet is placed in an external magnetic field, for example, in a coil with current, then under the influence of the external field, the domains will turn 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 sufficiently weak, then only a part of all domains whose magnetic fields approach the direction of the external field will flip over. 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 intensity
The relationship between the magnetic induction of a ferromagnetic substance and the strength of an external field can be depicted using a graph called the magnetization curve. At the bend of the curve graph, the rate of increase in magnetic induction decreases. After a bend, where the tension reaches a certain value, saturation occurs, and the curve slightly rises, 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 graphic 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 some indicator called the residual magnetic induction. The situation with the lagging of magnetic induction from the magnetizing force is called hysteresis.
To completely demagnetize the ferromagnetic core in the coil, it is necessary to give a reverse current, which will create the necessary tension. For different ferromagnetic substances, a segment of different lengths is needed. The larger it is, the more energy is needed 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, residual induction will be obtained. The phenomenon of residual magnetism is used to create permanent magnets from substances with a high residual magnetism. From substances that have the ability to remagnetize, cores are created for electrical machines and devices.
left hand rule
The force acting on a conductor with current has a direction determined by the rule of the left hand: when the palm of the virgin hand is located 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 force. This force is perpendicular to the induction vector and the current.
A current-carrying conductor moving in a magnetic field is considered a prototype of an electric motor, which changes electrical energy into mechanical energy.
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 right hand rule is used: when the right hand is located in the same way as in the example from the left, the magnetic lines enter the palm, and the thumb indicates the direction of movement of the conductor, the outstretched 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 of an electrical generator in which mechanical energy is converted into electrical energy.
It can be formulated differently: in a closed circuit, an EMF is induced, with any change in the magnetic flux covered by this circuit, the EDE in the circuit is numerically equal to the rate of change of the magnetic flux that covers this circuit.
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, with its magnetic field, prevents this change. If the turns of the coil are pierced by magnetic fluxes of different magnitudes, then the EMF induced on the whole coil is equal to the sum of the EMF 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, as well as 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, an EMF is induced inside the conductor. It appears in connection with a change in current in the conductor, therefore this phenomenon is called self-induction, and the EMF induced in the conductor is called self-induction EMF.
Flux linkage and magnetic flux depend not only on the strength of the current, but also on the size and shape of a given conductor, and the magnetic permeability of the surrounding substance.
conductor inductance
The coefficient of proportionality is called the inductance of the conductor. 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. It will depend on the size of the contour, its configuration and the magnetic permeability of the medium. In this case, the current strength in the circuit and the magnetic flux will not matter.
The above definitions and phenomena provide an explanation of 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.
Sources permanent magnetic fields (PMF) workplaces are permanent magnets, electromagnets, high-current DC systems (DC transmission lines, electrolyte baths, etc.).
Permanent magnets and electromagnets are widely used in instrumentation, magnetic washers for cranes, magnetic separators, magnetic water treatment devices, magnetohydrodynamic generators (MHD), nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR), as well as in physiotherapy practice.
The main physical parameters characterizing the PMF are field strength (N), magnetic flux (F) and magnetic induction (V). In the SI system, the unit of measurement of the magnetic field strength is ampere per meter (A/m), magnetic flux - Weber (Wb ), magnetic flux density (magnetic induction) - tesla (Tl ).
Changes in the state of health of persons working with PMF sources were revealed. Most often, these changes manifest themselves in the form of vegetative dystonia, asthenovegetative and peripheral vasovegetative syndromes, or a combination thereof.
According to the standard in force in our country (“Maximum Permissible Levels of Exposure to Permanent Magnetic Fields When Working with Magnetic Devices and Magnetic Materials” No. 1742-77), the PMF intensity at workplaces should not exceed 8 kA / m (10 mT). Permissible levels of PMF recommended by the International Committee on Non-Ionizing Radiation (1991) are differentiated by the contingent, the place of exposure and the time of work. For professionals: 0.2 Tl - when exposed to a full working day (8 hours); 2 Tl - with a short-term effect on the body; 5 Tl - with a short-term impact on the hands. For the population, the level of continuous exposure to PMF should not exceed 0.01 T.
Sources of electromagnetic radiation in the radio frequency range are widely used in various sectors of the economy. They are used to transmit information at a distance (broadcasting, radiotelephone communications, television, radar, etc.). In industry, electromagnetic radiation of the radio wave range is used for induction and dielectric heating of materials (hardening, melting, soldering, welding, metal spraying, heating of the internal metal parts of electrovacuum devices during pumping, drying wood, heating plastics, gluing plastic compounds, heat treatment of food products, etc.) . EMR are widely used in scientific research (radiospectroscopy, radio astronomy) and medicine (physiotherapy, surgery, oncology). In a number of cases, electromagnetic radiation occurs as a side unused factor, for example, near overhead power lines (OL), transformer substations, electrical appliances, including household ones. The main sources of EMF RF radiation into the environment are the antenna systems of radar stations (RLS), radio and television radio stations, including mobile radio systems and overhead power lines.
The human and animal body is very sensitive to the effects of RF EMF.
Critical organs and systems include: the central nervous system, eyes, gonads, and, according to some authors, the hematopoietic system. The biological effect of these radiations depends on the wavelength (or radiation frequency), generation mode (continuous, pulsed) and conditions of exposure to the body (constant, intermittent; general, local; intensity; duration). It is noted that biological activity decreases with increasing wavelength (or decreasing frequency) of radiation. The most active are centi-, deci-, and meter-wave bands. Injuries caused by RF EMR can be acute or chronic. Acute ones arise under the action of significant thermal radiation intensities. They are extremely rare - in case of accidents or gross violations of safety regulations at the radar. For professional conditions, chronic lesions are more typical, which are detected, as a rule, after several years of work with microwave EMR sources.
The main regulatory documents regulating the permissible levels of exposure to RF EMR are: GOST 12.1.006 - 84 “SSBT. Electromagnetic fields of radio frequencies.
Permissible levels" and SanPiN 2.2.4/2.1.8.055-96 "Electromagnetic radiation in the radio frequency range". They normalize the energy exposure (EE) for electric (E) and magnetic (H) fields, as well as the energy flux density (PEF) for a working day (Table 5.11).
Table 5.11.
Maximum Permissible Levels (MPL) per working day for employees
With EMI RF
| Parameter | Frequency bands, MHz | ||||
| Name | unit of measurement | 0,003-3 | 3-30 | 30-300 | 300-300000 |
| EE E | (W/m) 2 *h | - | |||
| uh n | (A/m) 2 *h | - | - | - | |
| ppe | (μW / cm 2) * h | - | - | - |
For the entire population under continuous exposure, the following MPs for electric field strength, V/m, have been established:
Frequency range MHz
0,03-0,30........................................................... 25
0,3-3,0.............................................................. 15
3-30.................................................................. 10
30-300............................................................... 3*
300-300000...................................................... 10
* Except for TV stations, the remote controls for which are differentiated according to
depending on the frequency from 2.5 to 5 V/m.
The number of devices operating in the radio frequency range includes video displays of personal computer terminals. Today, personal computers (PCs) are widely used in production, in scientific research, in medical institutions, at home, in universities, schools and even kindergartens. When used in the production of PCs, depending on technological tasks, they can affect the human body for a long time (within a working day). In domestic conditions, the time of using a PC is not at all controllable.
For PC video display terminals (VDT), the following EMI remote controls are installed (SanPiN 2.2.2.542-96 “Hygienic requirements for video display terminals, personal electronic computers and organization of work”) - table. 5.12.
Table 5.12. Maximum allowable levels of EMP generated by VDT
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 systematize all freely available 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 kinescope. I do not know the name of this person, but I know his nickname. He calls himself "The Wind". When a magnet is brought to the kinescope, a "honeycomb picture" is formed on the screen. You might think that the "grid" is a continuation of the kinescope grid. This is a method of visualizing the magnetic field.
I began to study the magnetic field with the help of a ferrofluid. 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 identical as possible to a simple magnet. The planet earth, in turn, is a copy of what it was formed from - the sun. We found out that a magnet is a kind of inductive 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.
The induction flow is the flow that originates at the poles of the planet and passes through us in a funnel geometry. The planet's north pole is the entrance to the funnel, the planet's south pole is the exit of the funnel. Some scientists call this stream the ethereal wind, saying that it is "of galactic origin." But this is not an "ethereal wind" and no matter what the ether is, 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 - to see him. It is possible to think 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 the best criterion is experience. Experience and more experience.
At home, I did simple experiments, but they allowed me to understand a lot. A simple cylindrical magnet ... And he twisted it this way and that. Poured magnetic fluid on it. It costs an infection, does not move. Then I remembered that on some forum I read that two magnets squeezed by the same poles in a sealed area increase the temperature of the area, and vice versa lower it with opposite poles. If temperature is a consequence of the interaction of fields, then why shouldn't it be the cause? I heated the magnet using a "short circuit" of 12 volts and a resistor by simply leaning the heated resistor against the magnet. The magnet heated up and the magnetic fluid began to twitch at first, and then completely became mobile. The magnetic field is excited by temperature. But how is it, I asked myself, because in the primers they 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 into the force of excitation of this field. Excellent Everything rotates and everything spins. But why does a rotating magnetic field have just such a geometry of rotation, and not some other one? At first glance, the movement is chaotic, but if you look through a microscope, you can see that in this movement system is present. The system does not belong to the magnet in any way, but only localizes it. In other words, a magnet can be considered as an energy lens that focuses perturbations in its volume.
The magnetic field is excited not only by an increase in temperature, but also by its decrease. I think that it would be more correct to say that the magnetic field is excited by a temperature gradient than by one of its specific signs. The fact of the matter is that there is no visible "restructuring" of the structure of the magnetic field. There is a visualization of a disturbance that passes through the region of this magnetic field. Imagine a perturbation that moves in a spiral from the north pole to the south through the entire volume of the planet. So the magnetic field of the magnet = the local part of this global flow. Do you understand? However, I'm not sure which particular thread...But the fact is that the thread. And there are not one stream, but two. The first is external, and the second is inside it and together with the first moves, but rotates in the opposite direction. The magnetic field is excited due to the temperature gradient. But we again distort the essence 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 into a state of unbalance. Those. we understand that the process of excitation is a constant process in which the magnetic field of the magnet is located. The gradient distorts the parameters of this process in such a way 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 perturbation of Ra and it seems to us to be moving. The temperature we apply to the magnet creates some kind of local imbalance in this focusable system. A certain instability appears in the spatial lattice, which is the honeycomb structure. After all, bees do not build their houses from scratch, but they stick around the structure of space with their building material. Thus, based on 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, includes an imbalance. At the moment, I am carefully studying the methods and means of managing this imbalance.
What is a magnetic field and how is it different from an electromagnetic field?
What is a torsion or energy-informational field?
It's all one and the same, but localized by different methods.
Current strength - there is a plus and a repulsive force,
tension is a minus and a force of attraction,
a short circuit, or let's say a local imbalance of the lattice - there is a resistance to this interpenetration. Or the interpenetration of father, son and holy spirit. Let's remember that the metaphor "Adam and Eve" is an old understanding of X and YG chromosomes. For the understanding of the new is a new understanding of the old. "Strength" - a whirlwind emanating from the constantly rotating Ra, leaving behind an informational weave of itself. Tension is another vortex, but inside the main vortex of Ra and moving along 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 out of itself and counterclockwise. When two vortices interpenetrate each other, they form a structure, like the layers of Jupiter, which move in different directions. It remains to understand the mechanism of this interpenetration and the system that is formed.
Approximate tasks for 2015
1. Find methods and means of unbalancing control.
2. Identify the materials that most affect 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 progress tool, we analyze the frequency spectra that are not included in the biological spectrum of human feelings. But we only register them, but we cannot "realize" them. Therefore, we do not see further than our senses can comprehend. Here is my main goal for 2015. Find a technique for technical awareness of a non-biological frequency spectrum in order to see the information basis of a person. Those. in fact, his soul.
A special kind of study is the magnetic field in motion. If we pour ferrofluid on a magnet, it will occupy the volume of the magnetic field and will be stationary. However, you need to check the experience of "Veterok" where he brought the magnet to the monitor screen. There is an assumption that the magnetic field is already in an excited state, but the volume of liquid kagba restrains it in a stationary state. But I haven't checked 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 coil axis, which can be found empirically.
I have done dozens of experiments with moving ferrofluid and set myself goals:
1. Reveal the geometry of fluid motion.
2. Identify the parameters that affect the geometry of this movement.
3. What is the place of fluid movement in the global movement of the planet Earth.
4. Whether the spatial position of the magnet and the geometry of movement acquired by it depend.
5. Why "ribbons"?
6. Why Ribbons Curl
7. What determines the vector of twisting of the tapes
8. Why the cones are displaced only by means of nodes, which are the vertices 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 the size of the cones is proportional to the volume and mass of the liquid poured onto the magnet
11. Why the cone is divided into two distinct sectors.
12. What is the place of this "separation" in terms of interaction between the poles of the planet.
13. How the fluid motion geometry depends on the time of day, season, solar activity, experimenter's intention, pressure and additional gradients. For example, a sharp 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 special services of 5 automatic weapons about the purpose, availability or storage of samples of this type of weapon.
16. What do the gutted pantries 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. (Masons, Jews, Vaticans, and other inconsistent formations).
17. Why there is always a leader among the cones. Those. a cone with a "crown" on top, which "organizes" the movements of 5,6,7 cones around itself.
cone at the moment of displacement. Jerk. "... only by moving the letter "G" I will reach him "...
If a hardened steel rod is inserted into a current-carrying coil, then, unlike an iron rod, it does not demagnetize after turning off the current, and retains magnetization for a long time.
Bodies that retain magnetization for a long time are called permanent magnets or simply magnets.
The French scientist Ampère explained the magnetization of iron and steel by electric currents that circulate inside each molecule of these substances. At the time of Ampere, nothing was known about the structure of the atom, so the nature of molecular currents remained unknown. Now we know that in every atom there are negatively charged particles-electrons, which, during their movement, create magnetic fields, and they cause the magnetization of iron and. become.
Magnets can have a wide variety of shapes. Figure 290 shows arcuate and strip magnets.
Those places of the magnet where the strongest are found magnetic actions are called the poles of a magnet(Fig. 291). Every magnet, like the magnetic needle known to us, necessarily has two poles; northern (N) and southern (S).
By bringing a magnet to objects made of various materials, it can be established that very few of them are attracted to the magnet. Good cast iron, steel, iron are attracted by a magnet and some alloys, much weaker - nickel and cobalt.
Natural magnets are found in nature (Fig. 292) - iron ore (the so-called magnetic iron ore). rich deposits we have magnetic iron ore in the Urals, in Ukraine, in the Karelian Autonomous Soviet Socialist Republic, the Kursk region and in many other places.
Iron, steel, nickel, cobalt and some other alloys acquire magnetic properties in the presence of magnetic iron ore. Magnetic iron ore allowed people to get acquainted with the magnetic properties of bodies for the first time.
If the magnetic needle is brought closer to another similar arrow, then they will turn and be set against each other with opposite poles (Fig. 293). The arrow also interacts with any magnet. Bringing a magnet to the poles of a magnetic needle, you will notice that the north pole of the arrow is repelled from the north pole of the magnet and is attracted to the south pole. The south pole of the arrow is repelled by the south pole of the magnet and is attracted by the north pole.
Based on the experiences described, make the following conclusion; different names Magnetic poles attract and like poles repel.
The interaction of magnets is explained by the fact that around every magnet there is a magnetic field. The magnetic field of one magnet acts on another magnet, and, conversely, the magnetic field of the second magnet acts on the first magnet.
With the help of iron filings, one can get an idea of the magnetic field of permanent magnets. Figure 294 gives an idea of the magnetic field of a bar magnet. Both the magnetic lines of the magnetic field of the current and the magnetic lines of the magnetic field of the magnet are closed lines. Outside the magnet, magnetic lines exit the north pole of the magnet and enter the south pole, closing inside the magnet.
Figure 295, a shows the magnetic magnetic field lines of two magnets, facing each other with the same poles, and in Figure 295, b - two magnets facing each other with opposite poles. Figure 296 shows the magnetic lines of the magnetic field of an arcuate magnet.
All of these pictures are easy to experience.
Questions. 1. What is the difference in magnetization with a current of a piece of iron and a piece of steel? 2, What bodies are called permanent magnets? 3. How did Ampere explain the magnetization of iron? 4. How can we now explain the molecular Ampère currents? 5. What is called the magnetic poles of a magnet? 6. Which of the substances you know are attracted by a magnet? 7. How do the poles of magnets interact with each other? 8. How can you determine the poles of a magnetized steel rod using a magnetic needle? 9. How can one get an idea of the magnetic field of a magnet? 10. What are the magnetic lines of the magnetic field of a magnet?
Magnetic fields occur naturally and can be created artificially. A person noticed their useful characteristics, which he learned to apply in everyday life. What is the source of the magnetic field?
Jpg?.jpg 600w
Earth's magnetic field
How the doctrine of the magnetic field developed
The magnetic properties of some substances were noticed in antiquity, but their study really began in medieval Europe. Using small steel needles, a scientist from France, Peregrine, discovered the intersection of magnetic lines of force 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 Ampère discovered and described the influence of an electric field on the occurrence of a magnetic field, and Faraday's discovery of electromagnetic induction established an inverse relationship.
What is a magnetic field
The magnetic field manifests itself in the 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.
Data-lazy-type="image" data-src="http://elquanta.ru/wp-content/uploads/2018/02/2-18-600x307.jpg?.jpg 600w, https://elquanta. ru/wp-content/uploads/2018/02/2-18-768x393..jpg 800w" sizes="(max-width: 600px) 100vw, 600px">
Magnetic field sources
The root cause of the occurrence of a magnetic field is identical for all sources: electric microcharges - electrons, ions or protons - have their own magnetic moment or are in directed motion.
Important! Mutually generate each other electric and magnetic fields that change over time. This relationship is determined by Maxwell's equations.
Magnetic field characteristics
The characteristics of the magnetic field are:
- Magnetic flux, a scalar quantity that determines how many magnetic field lines pass through a given section. Designated with the letter F. Calculated according to 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);
Data-lazy-type="image" data-src="http://elquanta.ru/wp-content/uploads/2018/02/3-17-600x450.jpg?.jpg 600w, https://elquanta. en/wp-content/uploads/2018/02/3-17.jpg 720w" sizes="(max-width: 600px) 100vw, 600px">
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. Quantitatively, magnetic induction is measured in teslas (Tl);
- MP tension (N). It is determined by the magnetic permeability of various media. In a vacuum, permeability is taken as unity. The direction of the intensity vector coincides with the direction of the magnetic induction. Unit of measurement - A / m.
How to represent a magnetic field
It is easy to see the manifestations of the 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 depending on the magnetic force;
- An alternative way of representing is to use lines of force. These lines never intersect, never start or stop anywhere, forming closed loops. The MF lines combine in more frequent regions where the magnetic field is strongest.
Important! The density of field lines indicates the strength of the magnetic field.
Although the MF cannot be seen in reality, the lines of force can be easily visualized in the real world by placing iron filings in the MF. 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.
Jpg?.jpg 600w, https://elquanta.ru/wp-content/uploads/2018/02/4-13.jpg 640w
Magnetic field lines
Magnetic field measurement
Since this is a vector quantity, there are two parameters for measuring MF: force and direction. Direction is easy to measure with a compass connected to the field. An example is a compass placed in the Earth's magnetic field.
Measurement of other characteristics is much more difficult. Practical magnetometers only appeared in the 19th century. Most of them work using the force that the electron feels when moving through the magnetic field.
Jpg?x15027" alt="(!LANG:Magnetometer" width="414" height="600">!}
Magnetometer
Very accurate measurement of small magnetic fields has become practical since the discovery in 1988 of giant magnetoresistance in layered materials. This discovery in fundamental physics was quickly applied to magnetic hard disk technology for data storage in computers, resulting in a thousandfold increase in storage capacity in just a few years.
In generally accepted measurement systems, MF is measured in tests (T) or in gauss (G). 1 T = 10000 gauss. Gauss is often used because the Tesla is too large a field.
Interesting. A small fridge magnet creates an MF equal to 0.001 T, and the Earth's magnetic field, on average, is 0.00005 T.
The nature of the magnetic field
Magnetism and magnetic fields are manifestations of the electromagnetic force. There are two possible ways how to organize an energy charge in motion and, consequently, 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 with distance. This is described by Ampère's law.
Jpg?.jpg 600w, https://elquanta.ru/wp-content/uploads/2018/02/6-9.jpg 720w
Ampère'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 right hand rule.
To use the rule, one must imagine that the wire is grasped by the right hand, and the thumb indicates the direction of the current. Then the other four fingers will show the direction of the magnetic induction vector around the conductor.
Jpeg?.jpeg 600w, https://elquanta.ru/wp-content/uploads/2018/02/7.jpeg 612w
Right hand rule
The second way to create an MF is to use the fact that electrons appear in some substances that have their own magnetic moment. This is how permanent magnets work:
- Although atoms often have many electrons, they are mostly connected in such a way that the total magnetic field of the pair cancels out. Two electrons paired in this way are said to have opposite spins. 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;
- Billions of electrons in atoms can be randomly oriented, and there will be no common magnetic field, no matter how many unpaired electrons the material has. It must be stable at a low temperature in order to provide an overall preferred electron orientation. The high magnetic permeability causes the magnetization of such substances under certain conditions outside the influence of the magnetic field. These are ferromagnets;
- Other materials may exhibit magnetic properties in the presence of an external magnetic field. The external field serves to equalize all electron spins, which disappears after the removal of the MF. These substances are paramagnetic. 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 the opposite sign: "minus" - at the earth's surface and "plus" - in the ionosphere. Between them is atmospheric air as an insulating gasket. The giant capacitor retains a constant charge due to the influence of the earth's magnetic field. Using this knowledge, it is possible to 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.
Data-lazy-type="image" data-src="http://elquanta.ru/wp-content/uploads/2018/02/8-3-592x600.jpg?.jpg 592w, https://elquanta. en/wp-content/uploads/2018/02/8-3.jpg 644w" sizes="(max-width: 592px) 100vw, 592px">
Tesla Coil
The Tesla coil will act as an electron emitter. The whole structure is connected together, and in order 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 get a large amount of electricity using this device.
Electricity and magnetism dominate many of the worlds surrounding man: from the most fundamental processes in nature to cutting-edge electronic devices.
Video
