Oersted's experiment in 1820. What does the deviation of the magnetic needle indicate when an electric circuit is closed? There is a magnetic field around a conductor carrying current. This is what the magnetic needle reacts to. Source magnetic field are moving electric charges or currents.
Oersted's experiment in 1820. What does the fact that the magnetic needle turned to indicate? This means that the direction of the current in the conductor has been reversed.
Ampere's experiment in 1820. How to explain the fact that current-carrying conductors interact with each other? We know that a magnetic field acts on a current-carrying conductor. Therefore, the phenomenon of interaction of currents can be explained as follows: electric current in the first conductor generates a magnetic field that acts on the second current and vice versa...
Unit of current If a current of 1 A flows through two parallel conductors 1 m long, located at a distance of 1 m from each other, then they interact with a force N.
The unit of current is 2 A. What is the current strength in the conductors if they interact with a force H?
What is a magnetic field and what are its properties? 1. MP is a special form of matter that exists independently of us and our knowledge about it. 2.MF is generated by moving electric charges and is detected by its effect on moving electric charges. 3. With distance from the MF source it weakens.
Properties of magnetic lines: 1. Magnetic lines are closed curves. What does this mean? If you take a piece of magnet and break it into two pieces, each piece will again have a "north" and a "south" pole. If you again break the resulting piece into two parts, each part will again have a “north” and a “south” pole. It doesn’t matter how small the resulting pieces of magnets are, each piece will always have a “north” and a “south” pole. It is impossible to achieve a magnetic monopole ("mono" means one, monopole means one pole). At least that's how it is modern point view on this phenomenon. This suggests that magnetic charges do not exist in nature. Magnetic poles cannot be separated.
2. A magnetic field can be detected by... A) by the action on any conductor, B) by the action on a conductor through which an electric current flows, C) a charged tennis ball suspended on a thin inextensible thread, D) on moving electric charges. a) A and B, b) A and B, c) B and C, d) B and D.
7.Which statements are true? A. Electric charges exist in nature. B. Magnetic charges exist in nature. B. Electric charges do not exist in nature. D. There are no magnetic charges in nature. a) A and B, b) A and B, c) A and D, d) B, C and D.
10. Two parallel conductors 1 m long, located at a distance of 1 m from each other, when an electric current flows through them, are attracted with a force N. This means that currents flow through the conductors... a) in opposite directions, 1 A each, b ) one direction at 1 A, c) opposite directions at 0.5 A, d) one direction at 0.5 A.
23. A magnetic needle will deviate if it is placed near... A) near a flow of electrons, B) near a flow of hydrogen atoms, C) near a flow of negative ions, D) near a flow of positive ions, E) near a flow of oxygen atom nuclei. a) all answers are correct, b) A, B, C, and D, c) B, C, D, d) B, C, D, E
3. The figure shows a cross-section of a conductor with current at point A, the electric current enters perpendicularly into the plane of the figure. Which of the directions presented at point M corresponds to the direction of vector B of the induction of the magnetic field of the current at this point? a) 1, b) 2, c) 3, 4)
We know that a current-carrying conductor creates a magnetic field around itself. A permanent magnet also creates a magnetic field. Will the fields they create be different? Undoubtedly they will. The difference between them can be seen clearly if you create graphical images of magnetic fields. The magnetic field lines will be directed differently.
In case current carrying conductor magnetic lines form closed concentric circles around a conductor. If we look at a cross-section of a current-carrying conductor and the magnetic field it creates, we will see a set of circles of different diameters. The figure on the left shows just a conductor carrying current.
The closer you are to the conductor, the stronger the effect of the magnetic field. As you move away from the conductor, the action and, accordingly, the strength of the magnetic field will decrease.
In case permanent magnet we have lines coming out of the south pole of the magnet, passing along the body of the magnet itself and entering its north pole.
Having sketched such a magnet and the magnetic lines of the magnetic field formed by it graphically, we will see that the effect of the magnetic field will be strongest near the poles, where the magnetic lines are most densely located. The picture on the left with two magnets just depicts the magnetic field of permanent magnets.
We will see a similar picture of the location of magnetic lines in the case of a solenoid or coil with current. The magnetic lines will have the greatest intensity at the two ends or ends of the coil. In all the above cases we had a non-uniform magnetic field. The magnetic lines had different directions, and their density was different.
If we look closely at the graphical representation of the solenoid, we will see that the magnetic lines are parallel and have the same density in only one place inside the solenoid.
The same picture will be observed inside the body of a permanent magnet. And if in the case of a permanent magnet we cannot “climb” inside its body without destroying it, then in the case of a coil without a core or solenoid, we get a uniform magnetic field inside them.
Such a field may be required by a person in a number of technological processes, so it is possible to design solenoids of sufficient size to allow the necessary processes to be carried out within them.
Graphically, we are accustomed to depicting magnetic lines as circles or segments, that is, we seem to see them from the side or along. But what if the drawing is created in such a way that these lines are directed towards us or at reverse side from us? Then they are drawn in the form of a dot or a cross.
If they are directed at us, then they are depicted as a point, as if it were the tip of an arrow flying towards us. In the opposite case, when they are directed away from us, they are drawn in the form of a cross, as if it were the tail of an arrow moving away from us.
“Determination of the magnetic field” - Using the data obtained during the experiments, fill out the table. J. Vern. When we bring a magnet to a magnetic needle, it turns. Graphic representation of magnetic fields. Hans Christian Oersted. Electric field. A magnet has two poles: north and south. The stage of generalization and systematization of knowledge.
“Magnetic field and its graphical representation” - Inhomogeneous magnetic field. Current coils. Magnetic lines. Ampere's hypothesis. Inside a strip magnet. Opposite magnetic poles. Polar lights. Magnetic field of a permanent magnet. Magnetic field. Earth's magnetic field. Magnetic poles. Biometrology. Concentric circles. Uniform magnetic field.
“Magnetic field energy” is a scalar quantity. Calculation of inductance. Constant magnetic fields. Relaxation time. Definition of inductance. Coil energy. Extracurrents in a circuit with inductance. Transient processes. Energy density. Electrodynamics. Oscillatory circuit. Pulsed magnetic field. Self-induction. Magnetic field energy density.
“Characteristics of the magnetic field” - Magnetic induction lines. Gimlet's rule. Rotate along the lines of force. Computer model of the Earth's magnetic field. Magnetic constant. Magnetic induction. Number of charge carriers. Three ways to set the magnetic induction vector. Magnetic field of electric current. Physicist William Gilbert.
“Properties of a magnetic field” - Type of substance. Magnetic induction of magnetic field. Magnetic induction. Permanent magnet. Some values of magnetic induction. Magnetic needle. Speaker. Magnetic induction vector module. Magnetic induction lines are always closed. Interaction of currents. Torque. Magnetic properties of matter.
“Movement of particles in a magnetic field” - Spectrograph. Manifestation of the Lorentz force. Lorentz force. Cyclotron. Determination of the magnitude of the Lorentz force. Test questions. Directions of Lorentz force. Interstellar matter. The task of the experiment. Changing parameters. Magnetic field. Mass spectrograph. Movement of particles in a magnetic field. Cathode ray tube.
There are 20 presentations in total
When constructing a picture of a magnetic field, the same rules are used as when constructing a picture of an electric field in electrostatics.
Magnetic field (or intensity) lines are magnetic field lines. The line where the magnetic potential is constant is called equipotential.
If a ferromagnetic body is introduced into a magnetic field, then the field lines will enter it at an angle 90 (i.e. the field is distorted). If a non-ferromagnetic body is introduced, then the field is not distorted.
Analogy of electrostatic (electric) and magnetic fields
There are two types of matches.
1) Identical distribution of linear charges in an electrostatic field and linear currents in a magnetic field.
In this case, the field patterns are similar, but the lines of force in the electrostatic field are equipotential in the magnetic field and vice versa, that is, the field pattern is rotated by an angle , the meaning of the lines changes.
2) Identical shape of the boundary equipotential surfaces in both fields. In this case, the field patterns are completely similar.
The physical nature of the fields is different, the electrostatic field is created by charges, the magnetic field is created by current, that is, in a magnetic field there is no concept of magnetic charge ( 
, a conditionally entered value).
For circuits (coils) with magnetic permeability 
and does not depend on the magnetic field strength, the flux linkage is proportional to the current
, Where
- proportionality coefficient, called inductance;
- electric current.
The flux linkage is:
, Where
Ф – magnetic flux;
w – number of turns.
From the above formulas it follows:
Inductance depends on the geometric dimensions of the circuit, the number of turns, and the properties of the medium, but does not depend on the amount of current flowing through the coil.
Method for determining inductance :
Conventionally, we assume that the current in the coil is known.
We express the magnetic flux through a known current.
We substitute the magnetic flux into the inductance formula, where the unknown currents cancel.
The method for calculating inductance is similar to the method for calculating capacitance
Example: Determine the inductance of a coil uniformly wound on a rectangular core, the inner radius of which is R 1, the outer radius R 2, height h, number of turns 
According to the law of total current, H is determined:
Flow through strip 
Full stream:
The flux linkage is:
The self-induction emf is proportional to the rate of change of current in this coil
-
Self-induced emf.
The phenomenon of induced emf in any circuit when the current changes in another circuit is called mutual induction, and the induced emf is mutual induction emf.
- EMF of mutual induction,
where, M is mutual inductance.
Let's understand together what a magnetic field is. After all, many people live in this field all their lives and don’t even think about it. It's time to fix it!
Magnetic field- a special type of matter. It manifests itself in the action on moving electric charges and bodies that have their own magnetic moment (permanent magnets).
Important: the magnetic field does not affect stationary charges! A magnetic field is also created by moving electric charges, or by a time-varying electric field, or by the magnetic moments of electrons in atoms. That is, any wire through which current flows also becomes a magnet!
A body that has its own magnetic field.
A magnet has poles called north and south. The designations "north" and "south" are given for convenience only (like "plus" and "minus" in electricity).
The magnetic field is represented by magnetic power lines. The lines of force are continuous and closed, and their direction always coincides with the direction of action of the field forces. If metal shavings are scattered around a permanent magnet, the metal particles will show a clear picture of the magnetic field lines coming out of the north pole and entering the south pole. Graphic characteristic of a magnetic field - lines of force.
The main characteristics of the magnetic field are magnetic induction, magnetic flux And magnetic permeability. But let's talk about everything in order.
Let us immediately note that all units of measurement are given in the system SI.
Magnetic induction B – vector physical quantity, which is the main force characteristic of the magnetic field. Denoted by the letter B . Unit of measurement of magnetic induction – Tesla (T).
Magnetic induction shows how strong the field is by determining the force it exerts on a charge. This force is called Lorentz force.
Here q - charge, v - its speed in a magnetic field, B - induction, F - Lorentz force with which the field acts on the charge.
F– a physical quantity equal to the product of magnetic induction by the area of the circuit and the cosine between the induction vector and the normal to the plane of the circuit through which the flux passes. Magnetic flux- scalar characteristic of the magnetic field.
We can say that magnetic flux characterizes the number of magnetic induction lines penetrating a unit area. Magnetic flux is measured in Weberach (Wb).
Magnetic permeability– coefficient determining magnetic properties environment. One of the parameters on which the magnetic induction of a field depends is magnetic permeability.
Our planet has been a huge magnet for several billion years. The induction of the Earth's magnetic field varies depending on the coordinates. At the equator it is approximately 3.1 times 10 to the minus fifth power of Tesla. In addition, there are magnetic anomalies where the value and direction of the field differ significantly from neighboring areas. Some of the largest magnetic anomalies on the planet - Kursk And Brazilian magnetic anomalies.
The origin of the Earth's magnetic field still remains a mystery to scientists. It is assumed that the source of the field is the liquid metal core of the Earth. The core is moving, which means the molten iron-nickel alloy is moving, and the movement of charged particles is the electric current that generates the magnetic field. The problem is that this theory ( geodynamo) does not explain how the field is kept stable.
The Earth is a huge magnetic dipole. The magnetic poles do not coincide with the geographic ones, although they are in close proximity. Moreover, the Earth's magnetic poles move. Their displacement has been recorded since 1885. For example, over the past hundred years, the magnetic pole in the Southern Hemisphere has shifted almost 900 kilometers and is now located in the Southern Ocean. The pole of the Arctic hemisphere is moving through the Arctic Ocean to the East Siberian magnetic anomaly; its movement speed (according to 2004 data) was about 60 kilometers per year. Now there is an acceleration of the movement of the poles - on average, the speed is growing by 3 kilometers per year.
What is the significance of the Earth's magnetic field for us? First of all, the Earth's magnetic field protects the planet from cosmic rays and solar wind. Charged particles from deep space do not fall directly to the ground, but are deflected by a giant magnet and move along its lines of force. Thus, all living things are protected from harmful radiation.
Several events have occurred over the course of Earth's history. inversions(shifts) magnetic poles. Pole inversion- this is when they change places. The last time this phenomenon occurred was about 800 thousand years ago, and in total there were more than 400 geomagnetic inversions in the history of the Earth. Some scientists believe that, given the observed acceleration of the movement of the magnetic poles, the next pole inversion should be expected in the next couple of thousand years.
Fortunately, a pole change is not yet expected in our century. This means that you can think about pleasant things and enjoy life in the good old constant field of the Earth, having considered the basic properties and characteristics of the magnetic field. And so that you can do this, there are our authors, to whom you can confidently entrust some of the educational troubles with confidence! and other types of work you can order using the link.
