For a long time, electric and magnetic fields were studied separately. But in 1820, the Danish scientist Hans Christian Oersted, during a lecture on physics, discovered that the magnetic needle turns near a conductor carrying current (see Fig. 1). This proved the magnetic effect of current. After conducting several experiments, Oersted discovered that the rotation of the magnetic needle depended on the direction of the current in the conductor.

Rice. 1. Oersted's experiment

In order to imagine the principle by which the magnetic needle rotates near a conductor with current, consider the view from the end of the conductor (see Fig. 2, the current is directed into the figure, - from the figure), near which the magnetic needles are installed. After passing current, the arrows will line up in a certain way, with opposite poles to each other. Since magnetic arrows line up tangent to magnetic lines, the magnetic lines of a straight conductor with current are circles, and their direction depends on the direction of the current in the conductor.

Rice. 2. Location of magnetic needles near a straight conductor with current

To more clearly demonstrate the magnetic lines of a current-carrying conductor, the following experiment can be performed. If iron filings are poured around a current-carrying conductor, then after some time the filings, once in the magnetic field of the conductor, will be magnetized and arranged in circles that encircle the conductor (see Fig. 3).

Rice. 3. Arrangement of iron filings around a current-carrying conductor ()

To determine the direction of magnetic lines near a current-carrying conductor, there is gimlet rule(right screw rule) - if you screw a gimlet in the direction of the current in the conductor, then the direction of rotation of the gimlet handle will indicate the direction of the lines magnetic field current (see Fig. 4).

Rice. 4. Gimlet rule ()

You can also use right hand rule- if you point the thumb of your right hand in the direction of the current in the conductor, then the four bent fingers will indicate the direction of the magnetic field lines of the current (see Fig. 5).

Rice. 5. Right hand rule ()

Both of these rules give the same result and can be used to determine the direction of current in the direction of magnetic field lines.

After discovering the phenomenon of the emergence of a magnetic field near a conductor carrying current, Oersted sent the results of his research to most of the leading scientists in Europe. Having received this data, the French mathematician and physicist Ampere began his series of experiments and after some time demonstrated to the public his experience of the interaction of two parallel conductors with current. Ampere established that if an electric current flows in one direction through two parallel conductors, then such conductors attract (see Fig. 6 b) if the current flows in opposite sides- conductors repel (see Fig. 6 a).

Rice. 6. Ampere's experiment ()

From his experiments, Ampere drew the following conclusions:

1. There is a magnetic field around a magnet, or a conductor, or an electrically charged moving particle.

2. A magnetic field acts with some force on a charged particle moving in this field.

3. Electric current is the directed movement of charged particles, so a magnetic field acts on a current-carrying conductor.

Figure 7 shows a wire rectangle, the direction of the current in which is shown by arrows. Using the gimlet rule, draw one magnetic line near the sides of the rectangle, indicating its direction with an arrow.

Rice. 7. Illustration for the problem

Solution

We screw an imaginary gimlet along the sides of the rectangle (conducting frame) in the direction of the current.

Near the right side of the frame, magnetic lines will exit the pattern to the left of the conductor and enter the plane of the pattern to the right of it. This is indicated by the arrow rule in the form of a dot to the left of the conductor and a cross to the right of it (see Fig. 8).

Similarly, we determine the direction of the magnetic lines near the other sides of the frame.

Rice. 8. Illustration for the problem

Ampere's experiment, in which magnetic arrows were installed around the coil, showed that when current flowed through the coil, the arrows to the ends of the solenoid were installed with different poles along imaginary lines (see Fig. 9). This phenomenon showed that there is a magnetic field near the current-carrying coil, and also that the solenoid has magnetic poles. If you change the direction of the current in the coil, the magnetic needles will reverse.

Rice. 9. Ampere's experiment. Formation of a magnetic field near a coil with current

To determine magnetic poles current coils used right hand rule for solenoid(see Fig. 10) - if you clasp the solenoid with the palm of your right hand, pointing four fingers in the direction of the current in the turns, then your thumb will show the direction of the magnetic field lines inside the solenoid, that is, to its north pole. This rule allows you to determine the direction of the current in the turns of the coil by the location of its magnetic poles.

Rice. 10. Right-hand rule for a current-carrying solenoid

Determine the direction of the current in the coil and the poles at the current source if, when current passes through the coil, the magnetic poles indicated in Figure 11 appear.

Rice. 11. Illustration for the problem

Solution

According to the right hand rule for the solenoid, we will grasp the coil in such a way that the thumb points to its north pole. The four bent fingers will indicate the direction of the current down the conductor, therefore the right pole of the current source is positive (see Fig. 12).

Rice. 12. Illustration for the problem

On this lesson We examined the phenomenon of the emergence of a magnetic field near a straight conductor with current and a coil with current (solenoid). The rules for finding magnetic lines of these fields were also studied.

References

1. A.V. Peryshkin, E.M. Gutnik. Physics 9. - Bustard, 2006.
2. G.N. Stepanova. Collection of problems in physics. - M.: Education, 2001.
3. A. Fadeeva. Physics tests (grades 7 - 11). - M., 2002.
4. V. Grigoriev, G. Myakishev Forces in nature. - M.: Nauka, 1997.

Homework

1. Internet portal Clck.ru ().
2. Internet portal Class-fizika.narod.ru ().
3. Internet portal Festival.1september.ru ().

For those who were not good at physics at school, the gimlet rule is still a real “terra incognita” today. Especially if you try to find a definition of a famous law on the Internet: search engines they will immediately give out a lot of tricky ones scientific explanations with complex circuits. However, it is quite possible to briefly and clearly explain what it is.

What is the gimlet rule?

Gimlet - a tool for drilling holes

It sounds like this: in cases where the direction of the gimlet coincides with the direction of the current in the conductor during translational movements, then at the same time the direction of rotation of the gimlet handle will be identical to it.

Looking for direction

To figure it out, you still have to remember school lessons. On them, physics teachers told us that electric current is movement. elementary particles, which at the same time carry their charge along the conductive material. Thanks to the source, the movement of particles in the conductor is directed. Movement, as we know, is life, and therefore nothing more than a magnetic field arises around the conductor, and it also rotates. But how?

The answer is given by this very rule (without using any special tools), and the result turns out to be very valuable, because depending on the direction of the magnetic field, a couple of conductors begin to act in completely different scenarios: either repel each other, or, on the contrary, rush towards each other.

Usage

The easiest way to determine the path of movement of magnetic field lines is to use the gimlet rule

You can imagine it this way - using the example of your own right hand and the most ordinary wire. We put the wire in our hand. We clench four fingers tightly into a fist. The thumb points up - like a gesture with which we demonstrate that we like something. In this “layout,” the thumb will clearly indicate the direction of movement of the current, while the other four indicate the path of movement of the magnetic field lines.

The rule is quite applicable in life. Physicists need it in order to determine the direction of the magnetic field of the current, calculate the mechanical rotation speed, the magnetic induction vector and the torque.

By the way, about the fact that the rule applies to the most different situations It also says that there are several interpretations of it at once - depending on each specific case being considered.

Much has been done since the creation of electricity. scientific work in physics to study its characteristics, features and influence on environment. The gimlet rule has contributed significant trace In the study of the magnetic field, the right-hand law for a cylindrical winding of a wire allows us to better understand the processes taking place in the solenoid, and the left-hand rule characterizes the forces affecting the current-carrying conductor. Thanks to the right and left hands, as well as mnemonics, these patterns can be easily learned and understood.

The gimlet principle

For quite a long time, the magnetic and electric characteristics of the field were studied separately by physics. However, in 1820, quite by accident, the Danish scientist Hans Christian Oersted discovered the magnetic properties of wires containing electricity while giving a lecture on physics at the university. The dependence of the orientation of the magnetic needle on the direction of current flow in the conductor was also discovered.

The experiment proves the presence of a field with magnetic characteristics around a current-carrying wire, to which a magnetized needle or compass reacts. The orientation of the “change” causes the compass needle to turn in opposite directions; the needle itself is located tangent to the electromagnetic field.

To identify the orientation of electromagnetic flows, the gimlet rule, or the law of the right screw, is used, which states that when screwing in a screw along the course of the flow of electric current in the shunt, the path of turning the handle will set the orientation of the EM flows of the background “change”.

It is also possible to use Maxwell's rule of the right hand: when the withdrawn finger of the right hand is oriented along the course of the flow of electricity, then the remaining closed fingers will show the orientation of the electromagnetic field.

Using these two principles, the same effect will be obtained, used to determine electromagnetic fluxes.

Right hand law for solenoid

The considered screw principle or Maxwell's law for the right hand is applicable to a straight wire with current. However, in electrical engineering there are devices in which the conductor is not located rectilinearly, and the law of screw is not applicable for it. First of all, this concerns inductors and solenoids. A solenoid, as a type of inductor, is a cylindrical winding of wire, the length of which is many times greater than the diameter of the solenoid. An inductance choke differs from a solenoid only in the length of the conductor itself, which can be several times smaller.

French specialist in mathematics and physics A-M. Ampere, thanks to his experiments, learned and proved that when the inductance of an electric current passed through the choke, the compass indicators at the ends of the cylindrical winding of the wire turned with their opposite ends along the invisible flows of the EM field. Such experiments have proven that a magnetic field is formed near an inductor carrying current, and a cylindrical winding of wire forms magnetic poles. The electromagnetic field excited by the electric current of a cylindrical winding of a wire is similar to the magnetic field of a permanent magnet - the end of the cylindrical winding of a wire from which EM flows emerge displays the north pole, and the opposite end is the south.

To recognize the magnetic poles and the orientation of EM lines in a current-carrying inductor, use the right-hand rule for the solenoid. It says that if you take this coil with your hand, place the fingers of your palm directly along the course of electron flow in the turns, your thumb, moved ninety degrees, will set the orientation of the electromagnetic background in the middle of the solenoid - its north pole. Accordingly, knowing the position of the magnetic poles of a cylindrical wire winding, it is possible to determine the path of electron flow in the turns.

Left hand law

Hans Christian Oersted after the discovery of the phenomenon of a magnetic field near a shunt in as soon as possible shared his results with most scientists in Europe. As a result of this, Ampere A.-M., using his methods, after a short period of time presented to the public an experiment on the specific behavior of two parallel shunts with electric current. The formulation of the experiment proved that wires placed in parallel, through which electricity flows in one direction, mutually move towards each other. Accordingly, such shunts will repel each other, provided that the “change” occurring in them will be distributed in different sides. These experiments formed the basis of Ampere's laws.

The tests allow us to voice the main conclusions:

1. A permanent magnet, a conductor with a “change”, an electrically charged moving particle have an EM region around them;
2. A charged particle moving in this region is subject to some influence from the EM background;
3. Electrical “change” is the oriented movement of charged particles; accordingly, the electromagnetic background affects the shunt with electricity.

The EM background affects the shunt with a “change” of a certain pressure called the Ampere force. This characteristic can be determined by the formula:

FA=IBΔlsinα, where:

• FA – Ampere force;
• I – intensity of electricity;
• B – vector of magnetic induction modulo;
• Δl – shunt size;
• α is the angle between direction B and the course of electricity in the wire.

Provided that the angle α is ninety degrees, then this force is greatest. Accordingly, if this angle is zero, then the force is zero. The contour of this force is revealed by the pattern of the left hand.

If you study the gimlet rule and the left hand rule, you will get all the answers to the formation of EM fields and their effect on conductors. Thanks to these rules, it is possible to calculate the inductance of the coils and, if necessary, form countercurrents. The principle of constructing electric motors is based on Ampere forces in general and the left-hand rule in particular.

Video

Using the rules of the left and right hands, you can easily find and determine the directions of current, magnetic lines, and other physical quantities.

Gimlet and right hand rule

The gimlet rule was first formulated by the famous physicist Peter Buravchik. It is convenient to use to determine the direction of tension. So, the wording of the rule is as follows: in the case when a gimlet, moving translationally, is screwed in the direction electric current, the direction of the handle of the gimlet itself must coincide with the direction of the magnetic field. This rule can be used with a solenoid: we grasp the solenoid, our fingers should point in the same direction as the current, that is, show the path of the current in the turns, then we stick out the thumb of our right hand, it points to the desired path of the magnetic induction lines.

The rule of the right hand is used according to statistics much more often than the rule of the gimlet, partly due to a more understandable formulation, it says: we grasp the object with our right hand, while the clenched fingers of the fist should show the direction of the magnetic lines, and the thumb protruded approximately 90 degrees should show the direction electric current. If a moving conductor is present: the arm should be rotated so that power lines of this field were perpendicular to the palm (90 degrees), the protruding thumb should point to the path of movement of the conductor, then 4 bent fingers will point to the path of the induction current.

Left hand rule

The left-hand rule has two formulations. The first formulation states: the hand should be positioned so that the remaining curled fingers of the hand indicate the path of electric current in a given conductor, the induction lines should be perpendicular to the palm, and the extended thumb of the left hand indicates the force exerted on a given conductor. The following formulation reads: the four bent fingers of the hand, in addition to the thumb, are located precisely according to the movement of negatively charged or positively charged electric current, and the induction lines should be directed perpendicularly (90 degrees) into the palm, in this case, the exposed thumb in this case should point to the flow Ampere forces or Lorentz forces.