Magnetic field induction - the value determined by the parameters of the medium, showing the magnitude of the force with which the field acts on the compass needle, a conductor with a current or ferromagnetic materials when the object is presented. The history of the development of the subject is described in detail in the section Magnetic induction( synonyms), here we focus entirely on the practical part, the terms.
Magnetic field and characteristics
Oersted discovered the deviation of the compass needle with a wire with an electric current, magnetism was then considered an independent phenomenon. Showed the properties of solids. Hilbert wrote: magnetism in comparison with weak and unstable electricity has strength and inviolability. The field passes freely objects. Therefore, it was necessary to characterize the substance. It took time to recreate the picture. Today, as indicated by the Magnetic Induction section, two models dominate: the
Initially, the strength of the interaction of two conductors with current was investigated. As Ampere demonstrated the discovery of Oersted to a meeting of the scientific community, researchers began digging. During the discussions, Laplace suggested: the effect of the phenomenon can be strengthened by flexing the conductor. So there appeared( in 1820) an inductance coil in Schweiger’s multiplier( galvanometer), the prototype of an electromagnet in Arago’s experiments with the magnetisation of a needle entangled with wire, the discharge of a Leyden jar. The discovery of the law of Bio-Savar became significant( see fig.).Associates the characteristic of the magnetic field of a wire with a current and some other values.
The left side of equality contains the element of induction. A small fraction of the common field created by the elementary( small) segment of the conductor dl. The magnitude is determined by the strength of the current, the distance to the point in question, the angle between the vectors l and B. Agree that the terms sound vague, it is necessary to consider the key concepts. In modern physics, the phenomena of a magnetic field are explained by visual experiments with the active participation of an electroscope. A physical device, invented long before the events described( mid-XVIII century), which allows to determine the presence of a static charge on the object.
The first electroscope consisted of a tree ball suspended on an arc that resembled a fishing hook set upside down. As a result, the thread went freely to the side. The ball was rubbed with wool, a charge was formed, interacting with others. The process describes the Coulomb's law. Let us return to the demonstration of the magnetic field by modern physics. The tutorial uses simple examples:
- A charged electroscope ball is brought to a conductor with current. There is some interaction.
- The direction of the current change: the picture remains the same.
- Remove the current at all - the interaction is evident.
Make a conclusion: the wire carrying the current with the fixed ball of the electroscope does not interact by itself. There is an electrification of influence. The wire acquires a static charge from the ball, there is an interaction. Consequently, the electric field is concentrated inside the conductor, does not go beyond. According to the axiom:
Magnetic is called the force of interaction of a conductor under current with another conductor, a compass needle, some materials and objects.
Magnetic Field Lines
The magnetic field does not affect the stationary charge, it acts on the moving electricity. When Bio experimentally, Savard later mathematically formulated the law, we needed models describing the interaction of the new phenomenon with the objects of the material world. It should be clearly understood, although the law of Bio-Savar contains the magnitude of magnetic induction, at the time of 1820 was simply absent in the scientific field. A certain measure of the field, what exactly represented, nobody could say exactly. Gaussian GHS appeared in 1832, devoid of many physical quantities.
The treatise of 1600 by Hilbert suggested the structure of the tension lines. To clarify the circumstances, he actively used a magnetic needle, created a ball of ore, proved the similarity of the field of an object to the Earth. By the nature of the interaction put forward an idea: one pole emits a certain substance, the other - absorbs. Being content with arguments, in 1644 Rene Descartes created one of the first pictures of the magnetic field, using small metal filings. Experience does not disdain today's textbooks of physics. The magnetic field lines are smooth, closed at the poles, the induction vector is tangent at each point.
In accordance with the law of Bio-Savart, the existing knowledge of Poisson in 1824 creates the first field model. Operates with dipoles, is removed from the environment of the propagation of the phenomenon. Ampere goes a different way, representing the sources of the magnetic field, elementary circulating charges. Through experiments, she notes: the strength of the interaction depends on the environment, thus making a contribution. Both were right.
The existence of a magnetic field regardless of the environment, the force of action on objects in some materials varies. To describe the quantitative measure of the change, we introduced a unit of relative magnetic permeability. Shows the difference in the strength of interaction in comparison with the process going on in a vacuum. According to this approach, the materials form three groups:
- Paramagnetic materials slightly increase the intensity H, the magnetic field induction is slightly larger than in a vacuum. Substances lose properties acquired as a result of interaction as soon as the source of changes disappears.
- Diamagnetics weaken the field. Tension H is higher than induction B. The class of substances includes: table salt, naphthalene, bismuth. The field is weakened, the magnetic susceptibility is negative.
- Ferromagnetics multiply tensions, induction is much higher than H. For this reason, they are used to manufacture transformer cores.
Now we will explain: the field strength H characterizes the properties of the source of magnetism, it exists in any environment. Induction shows the ability of the phenomenon to induce EMF in conductors. Where did the name come from? Although in practice induction plays a primary role, it is convenient to carry out cases with the simultaneous use of different media from the standpoint of field strength. The value is multiplied by the value of the magnetic permeability of the medium.
By the way, Michael Faraday, not knowing the facts, chose a ferromagnet( mild steel) for a successful experience with a toroidal transformer. Due to this, successfully managed to fix the phenomenon of induction. It takes place to be airborne, but not so noticeable. Ferromagnetic multiplies multiply the ability of the field to induce a response in the form of a secondary voltage of the transformer secondary winding. The permeability of some materials is thousands of units.
The drawings agreed on the magnetic field lines to be applied the more densely, the higher the induction. Per unit area( for example, square centimeter) accounts for as much as the value of a physical quantity in T.Helps to visually assess the density of the field. The number of lines covered by the area of the figure reflects the amount of work to move the electric charge within it. The thesis is reflected by the Faraday law( see fig.), Where the value of the magnetic induction density measured by the Weber appears.
Laws and Phenomena Associated with Magnetic Field Induction
Magnetic induction and magnetic field induction are synonymous words. This parameter characterizes the source properties and environment attributes. Therefore, it is time to consider the laws related to the phenomenon. The first thing that comes to mind is to look through a physics textbook, we believe that readers can do it individually. We propose to consider the phenomenon that has passed unnoticed by Wikipedia and some textbooks of physics, the majority.
Earth's magnetic poles are the exact opposite of the true. The point is not that the magnetic poles are deviated from the geographical. Not! Directly opposite in location to the poles with which the physicist operates. Therefore, no matter what textbook, everywhere the compass needle points to the south. Although the authors are trying to exclude pictures, which could be uniquely set. Let's look at two of them( photo Physics course Zhdanov LS and Maradzhanyan V.A.):
- The first shows: the compass needle tracks the direction of the field with the north pole.
- The second demonstrates the rule of the left hand, at the same time we notice: the field is directed from north to south.
An illustration is sought that clearly shows: the northern end of a ferromagnet looks to the south. The true North Pole is not in the Arctic, as people used to think, in the vast Antarctica. Another contradiction of physics, the second is the assumption that the current is formed by positive charges. I would like to make another report today.
Earth's magnetic poles periodically change places!
Yes, they do it, the last shift was about 780,000 years ago( information obtained from the analysis of rocks).Although sometimes the process occurred more often. In August 1999, the Age of Aquarius began, with the next change of poles coming. For a century up to this date, the magnetic north pole shifted annually by 10 km, by the beginning of the 2000s - by as much as 50. The figure is constantly growing. Among the scientific circles there are alarmists claiming that a polarity reversal every time causes the collapse of the biosphere: supposedly, so dinosaurs died.
Experts give the ongoing process 40 - 100 years, then. .. the physical concepts will become true: the compass needle will look exactly in the right direction. Scientific intuition of the era of technical revolution? It is impossible to say for sure, but it is time for sailors and pilots to correct the magnetic declination( the difference between the direction to the geographical and magnetic poles).Consoles one thing: most of the objects are guided by the readings of GPS devices( satellite navigation with the use of terrestrial broadcasting stations).
Magnetic storms are provoked by changes in the sun. A natural cataclysm when the compass needle starts to behave unpredictably. The field has 11 and 100-year cycles, have little effect on the weather, because most of humanity is imperceptible. We will answer skeptics: the magnetic field is the only defense of humanity against the action of cosmic radiation, it’s time to seriously think about the preservation of the planet. The ozone layer will be particularly hard hit, followed by the microscopic ocean population. In fact, the future of the planet depends on the adaptability of aquatic life to change.
The first 3-D field mapping performed the Magsat satellite in 1980, then after a long break in 1999, Oersted( satellite) took up the challenge. The necessity of launching is caused by the arrival of the Age of Aquarius and the events described above. While the study of the magnetic shield of the Earth is engaged in satellite grouping Swarm. It is believed that the changes are triggered by fluctuations in the composition of the core of the planet, scientists want to find the exact dependencies. After half a year of work( beginning of 2014), the research results became of concern: the magnetic field weakens, changes the configuration.