The first to formulate the gimlet rule was Peter Gimlet. This rule is very convenient if you need to determine such a characteristic magnetic field, like directionality .

The gimlet rule can only be used if the magnetic field is located rectilinearly with respect to the current-carrying conductor.

The gimlet rule states that the direction of the magnetic field will coincide with the direction of the handle of the gimlet itself, if the gimlet with a right-hand thread is screwed in the direction of the current.

The application of this rule is also possible in the solenoid. Then the rule of the gimlet sounds like this: the thumb protruding finger of the right hand will indicate the direction of the lines of magnetic induction, if you wrap around the solenoid so that the fingers point to the direction of the current in the turns.

Solenoid - is a coil with tightly wound turns. A prerequisite is that the length of the coil must be significantly larger than the diameter.

The right hand rule is the opposite of the gimlet rule, but with a more convenient and understandable formulation, which is why it is used much more often.

The rule of the right hand sounds like this - grab the element under study with your right hand so that the fingers of a clenched fist indicate the direction, in which case, when moving forward in the direction of the magnetic lines, a large finger bent 90 degrees relative to the palm of your hand will indicate the direction of the current.

If the task describes a moving conductor, then the rule of the right hand is formulated as follows: position the hand so that the field lines of force enter the palm perpendicularly, and the thumb, extended perpendicularly, should indicate the direction of movement of the conductor, then the protruding four remaining fingers will be directed in the same way like the induced current.

left hand rule

Position the left palm so that four fingers indicate the direction of the electric current in the conductor, while the lines of induction should enter the palm at an angle of 90 degrees, then the bent thumb will indicate the direction of the force acting on the conductor.

Most often, this rule is used to determine the direction in which the conductor will deviate. This refers to the situation when a conductor is placed between two magnets and a current is passed through it.

Write out the Biot-Savart-Laplace law from the textbook. This law allows you to calculate the magnitude and direction of the magnetic induction vector in any general case. The basis for calculating the magnetic field according to this rule is the currents that create this field. Moreover, the lengths of the sections through which the current flows can be made arbitrarily small up to elementary values, thus increasing the accuracy of the calculation.

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The right screw rule is used in the terminology of one of the sections of physics that studies electromagnetic phenomena. This rule is used to determine the direction of the magnetic field.

You will need

• Physics textbook, pencil, sheet of paper.

Instruction

Read in the textbook for the eighth grade what the rules of the right screw sound like. This rule is also called the gimlet rule or the right hand rule, which indicates its semantic nature. So, one of the formulations of the right screw rule says that in order to understand how the magnetic field located around a current-carrying conductor is directed, it is necessary to imagine that the translational movement of a rotating screw coincides with the direction of the current in the conductor. The direction of rotation of the screw head in this case should indicate the direction of the magnetic field of a straight current-carrying conductor.

Please note that the wording and understanding of this rule becomes clearer if we imagine a gimlet instead of a screw. Then the direction of rotation of the gimlet handle is taken as the direction of the magnetic field.

Remember the solenoid. As you know, it is an inductor wound on a magnetic core. The coil is connected to a current source, as a result of which a uniform magnetic field of a certain direction is formed inside it.

Draw a solenoid schematically on a piece of paper from the side of its end. In fact, you will get an image of a circle. Indicate on the circle representing the turns of the coil, the direction of the current in the conductor in the form of an arrow (clockwise). Now it remains to understand in the direction of the current where the lines of the magnetic field are directed. In this case, they can be directed either from you or towards you.

Imagine that you are tightening some kind of screw or screw, rotating it in the direction of current flow in the solenoid. The translational movement of the screw shows the direction of the magnetic field inside the solenoid. If the direction of the current is clockwise, then the vector of the magnetic field is directed away from you.

Much has been done since the invention of electricity. scientific work in physics to study its characteristics, features and influence on environment. The gimlet rule has made its significant mark on the study of the magnetic field, the law of the right hand for a cylindrical winding of a wire allows a deeper understanding of the processes taking place in the solenoid, and the left hand rule characterizes the forces that affect the conductor with current. Thanks to the right and left hands, as well as mnemonic techniques, these patterns can be easily studied and understood.

gimlet principle

For quite a long time, the magnetic and electrical 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 a wire with electricity during 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 found.

The conducted 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 flow of the "change" makes the compass needle turn in opposite directions, the arrow itself is located tangentially to the electromagnetic field.

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

It is also possible to use Maxwell's rule of the right hand: when the retracted finger of the right hand is oriented along the course of the flow of electricity, then the remaining clenched 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 regularity 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 straight, and the law of the screw is not applicable to it. First of all, this applies to inductors and solenoids. A solenoid, as a kind of inductor, is a cylindrical winding of wire, the length of which is many times greater than the diameter of the solenoid. The inductor inductor differs from the solenoid only in the length of the conductor itself, which can be several times smaller.

French mathematician and Physics A-M. Ampère, thanks to his experiments, found out and proved that when the electric current passed through the inductance choke, the compass pointers at the ends of the cylindrical winding of the wire turned their reverse ends along the invisible flows of the EM field. Such experiments proved that a magnetic field is formed near the inductor with current, and the cylindrical winding of the wire forms magnetic poles. The electromagnetic field excited by the electric current of the cylindrical winding of the wire is similar to the magnetic field of a permanent magnet - the end of the cylindrical winding of the wire, from which the EM fluxes exit, represents the north pole, and the opposite end is the south.

To recognize the magnetic poles and the orientation of the EM lines in the inductor with current, the right-hand rule for the solenoid is used. It says that if you take this coil with your hand, place the fingers of the palm directly in the course of the flow of electrons in the turns, the 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 the cylindrical winding of the wire, it is possible to determine the path of electron flow in the turns.

left hand law

Hans Christian Oersted, after discovering the phenomenon of a magnetic field near a shunt, quickly shared his results with most scientists in Europe. As a result, Ampere A.-M., using his methods, after a short period of time revealed 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” flowing in them will be distributed in different directions. These experiments formed the basis of Ampère's laws.

Tests allow us to voice the main conclusions:

1. A permanent magnet, a "reversible" conductor, 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 "reversal" is the oriented movement of charged particles, respectively, the electromagnetic background acts on the shunt with electricity.

The EM background influences the shunt with a "change" of some kind of pressure called the Ampère force. This characteristic can be determined by the formula:

FA=IBΔlsinα, where:

• FA is the Ampere force;
• I is the intensity of electricity;
• B is the vector of magnetic induction modulo;
• Δl is the 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 the greatest. Accordingly, if this angle 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 construction of electric motors is based on the Ampère forces in general and the left hand rule in particular.

Video

In physics for grade 11 (Kasyanov V.A., 2002),
a task №32
to chapter " Magnetism. A magnetic field. MAIN PROVISIONS».

Magnetic induction vector

Electric current has a magnetic effect. Thus, a magnetic field is generated by moving charges.

Magnetic induction vector- vector physical quantity, the direction of which at a given point coincides with the direction indicated at this point by the north pole of a free magnetic needle.

Modulus of magnetic induction vector- a physical quantity equal to the ratio of the maximum force acting from the side of the magnetic field on a segment of the conductor with current, to the product of the current strength and the length of the conductor segment:

The unit of magnetic induction is tesla (1 T).

Gimlet rule for direct current: if you screw the gimlet in the direction of the current in the conductor, then the direction of the speed of movement of the end of its handle coincides with the direction of the magnetic induction vector at this point.

Right hand rule for direct current: if you cover the conductor with your right hand, pointing the bent thumb along the current, then the tips of the remaining fingers at this point will show the direction of the induction vector at this point.

The principle of superposition of magnetic fields: the resulting magnetic induction at a given point is the sum of the magnetic induction vectors created by various currents at this point:

Gimlet rule for a coil with current (loop current): if you rotate the gimlet handle in the direction of the current in the coil, then the translational movement of the gimlet coincides with the direction of the magnetic induction vector created by the current in the coil on its axis.

Lines of magnetic induction- lines, tangents to which at each point coincide with the direction of the magnetic induction vector. The lines of magnetic induction are always closed: they have no beginning and no end. Magnetic field - a vortex field, i.e. a field with closed lines of magnetic induction

Magnetic flux (flux of magnetic induction) through the surface of a certain area - a physical quantity equal to the scalar product of the magnetic induction vector and the area vector:

The unit of magnetic flux is weber (1 Wb) 1 Wb \u003d 1 Tl.m 2.

Ampere's law: the force with which the magnetic field acts on a segment of a current-carrying conductor placed in it is equal to the product of the current strength, magnetic induction, the length of the conductor segment and the sine of the angle between the current directions and the magnetic induction vector:

In a uniform magnetic field, a closed circuit tends to settle in such a way that the direction of its own induction coincides with the direction of the external induction.

Lorentz force- the force acting on a charged particle moving at a speed v from the side of the magnetic field B:

where q is the charge of the particle, and is the angle between the particle's velocity and the magnetic field induction.

The direction of the Lorentz force determines left hand rule: if the left hand is positioned so that four outstretched fingers indicate the direction of the positive charge velocity (or opposite to the negative charge velocity), and the magnetic induction vector enters the palm, then the thumb bent (in the plane of the palm) by 90 ° will show the direction of the force acting on given charge.

A charged particle flying into a uniform magnetic field parallel to the lines of magnetic induction moves uniformly along these lines. A charged particle flying into a uniform magnetic field in a plane perpendicular to the lines of magnetic induction moves in this plane in a circle. Conductors located in parallel, through which currents flow in one direction, attract, and in opposite directions they repel. Magnetic fields created by currents I 1, I 2, flowing through infinitely long parallel conductors located at a distance r from each other, lead to the appearance of an interaction force on each segment of conductors with a length Δl

where k m - coefficient of proportionality, k m \u003d 2 10 -7 N / A 2

The unit of current strength is ampere (1 A) The direct current strength is 1 A if the current, flowing through two parallel conductors of infinite length and negligible circular cross-sectional area, located in vacuum at a distance of 1 m from one another, causes on a segment of the conductor with a length 1 m interaction force equal to 2 10 -7 N

The magnetic field induction decreases with increasing distance to the conductor with current. The interaction of conductors with current is a consequence of the magnetic interaction of moving charges in conductors. Under the influence of a magnetic force, opposite charges moving in parallel in opposite directions are attracted, and like charges are repelled.

Loop inductance(or coefficient of self-induction) - a physical quantity equal to the coefficient of proportionality between the magnetic flux through the area bounded by the conductor circuit and the current strength in the circuit. The unit of inductance is henry (1 H)

Magnetic field energy, created during the flow of current I through a conductor with inductance L, is equal to

Magnetic permeability of the medium- a physical quantity showing how many times the induction of a magnetic field in a homogeneous medium differs from the magnetic induction of an external (magnetizing) field in a vacuum.

Diamagnets, paramagnets, ferromagnets- the main classes of substances with sharply different magnetic properties

Diamagnetic- substance in which the external magnetic field is slightly weakened (μ<= 1)

Paramagnetic a substance in which the external magnetic field is slightly enhanced (μ >= 1)

Ferromagnetic- a substance in which the external magnetic field is greatly enhanced (μ >> 1)

Magnetization curve- dependence of the intrinsic magnetic induction on the induction of the external magnetic field

Coercive force is the magnetic induction of the external field required to demagnetize the sample

Magnetically hard ferromagnets- ferromagnets with high residual magnetization Magnetically soft ferromagnets- ferromagnets with low residual magnetization Hysteresis loop- closed curve of magnetization and demagnetization of a ferromagnet Curie temperature- the critical temperature above which the transition of a substance from a ferromagnetic state to a paramagnetic state occurs

Entering adulthood, few people remember the school physics course. However, sometimes it is necessary to delve into the memory, because some knowledge gained in youth can greatly facilitate the memorization of complex laws. One of these is the right and left hand rule in physics. Its application in life allows you to understand complex concepts (for example, to determine the direction of the axial vector with a known basis). Today we will try to explain these concepts and how they work in a language accessible to a simple layman who graduated a long time ago and forgot unnecessary (as it seemed to him) information.

Read in the article:

The wording of the gimlet rule

Piotr Buravchik is the first physicist to formulate the left hand rule for various particles and fields. It is applicable both in electrical engineering (it helps to determine the direction of magnetic fields), and in other areas. It will help, for example, to determine the angular velocity.

Gimlet rule (right hand rule) - this name is not associated with the name of the physicist who formulated it. More name relies on a tool that has a certain direction of the auger. Usually, a gimlet (screw, corkscrew) has a so-called. the thread is right-handed, the drill enters the ground clockwise. Consider the application of this statement to determine the magnetic field.

Need to squeeze right hand in a fist, thumb up. Now we slightly unclench the other four. They show us the direction of the magnetic field. In short, the gimlet rule has the following meaning - by screwing the gimlet along the direction of the current, we will see that the handle rotates in the direction of the line of the magnetic induction vector.

The right and left hand rule: application in practice

In considering the application of this law, let's start with the right hand rule. If the direction of the magnetic field vector is known, with the help of a gimlet one can do without knowledge of the law of electromagnetic induction. Imagine that the screw moves along the magnetic field. Then the direction of current flow will be "along the thread", that is, to the right.

Let's pay attention to the permanent controlled magnet, the analog of which is the solenoid. At its core, it is a coil with two contacts. It is known that the current moves from "+" to "-". Based on this information, we take the solenoid in the right hand in such a position that 4 fingers indicate the direction of the current flow. Then the outstretched thumb will indicate the vector of the magnetic field.

The left hand rule: what can be determined using it

Do not confuse the rules of the left hand and gimlet - they are designed for completely different purposes. With the help of the left hand, two forces can be determined, or rather, their direction. It:

• Lorentz force;
• ampere power.

Let's try to figure out how it works.

The left hand rule for Ampère's power: what it is

Arrange left hand along the conductor so that the fingers point in the direction of current flow. The thumb will point in the direction of the Ampère force vector, and in the direction of the hand, between the thumb and forefinger, the magnetic field vector will be directed. This will be the left hand rule for the ampere force, the formula of which looks like this:

Left hand rule for the Lorentz force: differences from the previous one

We arrange the three fingers of the left hand (thumb, index and middle) so that they are at right angles to each other. The thumb, directed in this case to the side, will indicate the direction of the Lorentz force, the index finger (pointed down) - the direction of the magnetic field (from north pole to the south), and the middle one, located perpendicular to the side of the large one, is the direction of the current in the conductor.

The formula for calculating the Lorentz force can be seen in the figure below.

Conclusion

Having dealt once with the rules of the right and left hand, the dear reader will understand how easy it is to use them. After all, they replace the knowledge of many laws of physics, in particular, electrical engineering. The main thing here is not to forget the direction of current flow.

We hope that today's article was useful to our dear readers. If you have any questions, you can leave them in the discussions below. The editors of the site will be happy to answer them as soon as possible. Write, communicate, ask. And we, in turn, invite you to watch a short video that will help you more fully understand the topic of our conversation today.

It often happens that the problem cannot be solved due to the fact that the necessary formula is not at hand. Deriving a formula from the very beginning is not the fastest thing, and every minute counts.

Below we have collected together the basic formulas on the topic "Electricity and Magnetism". Now, when solving problems, you can use this material as a reference, so as not to waste time searching for the necessary information.

Magnetism: definition

Magnetism is the interaction of moving electric charges that occurs through a magnetic field.

Field – special form matter. Within the framework of the standard model, there are electrical, magnetic, electromagnetic fields, the nuclear force field, the gravitational field, and the Higgs field. Perhaps there are other hypothetical fields that we can only guess about or not guess at all. Today we are interested in the magnetic field.

Magnetic induction

Just as charged bodies create an electric field around them, moving charged bodies generate a magnetic field. The magnetic field is not only created by moving charges ( electric shock), but also affects them. In fact, a magnetic field can only be detected by its effect on moving charges. And it acts on them with a force called the Ampere force, which will be discussed later.

Before we begin to give specific formulas, we need to talk about magnetic induction.

Magnetic induction is a power vector characteristic of a magnetic field.

It is marked with the letter B and measured in Tesla (Tl) . By analogy with tension for electric field E magnetic induction shows how strong the magnetic field acts on the charge.

By the way, you will find many interesting facts on this topic in our article about.

How to determine the direction of the magnetic induction vector? Here we are interested in the practical side of the issue. The most common case in problems is a magnetic field created by a conductor with current, which can be either straight, or in the form of a circle or coil.

To determine the direction of the magnetic induction vector, there is right hand rule. Get ready to use abstract and spatial thinking!

If you take the conductor in your right hand so that the thumb points in the direction of the current, then the fingers bent around the conductor will show the direction of the magnetic field lines around the conductor. The vector of magnetic induction at each point will be directed tangentially to the lines of force.

Amp power

Imagine that there is a magnetic field with induction B. If we place a conductor of length l , through which current flows I , then the field will act on the conductor with the force:

That's what it is ampere power . Corner alpha is the angle between the direction of the magnetic induction vector and the direction of the current in the conductor.

The direction of the Ampère force is determined by the rule of the left hand: if you place the left hand so that the lines of magnetic induction enter the palm, and the outstretched fingers indicate the direction of the current, the thumb set aside will indicate the direction of the Ampère force.

Lorentz force

We found out that the field acts on a conductor with current. But if this is so, then initially it acts separately on each moving charge. The force with which a magnetic field acts on a person moving in it electric charge, is called Lorentz force . It is important to note here the word "moving", so the magnetic field does not act on stationary charges.

So, a particle with a charge q moves in a magnetic field with induction AT with speed v , a alpha is the angle between the particle velocity vector and the magnetic induction vector. Then the force acting on the particle is:

How to determine the direction of the Lorentz force? Left hand rule. If the induction vector enters the palm, and the fingers point in the direction of the velocity, then the bent thumb will show the direction of the Lorentz force. Note that this is how the direction is determined for positively charged particles. For negative charges, the resulting direction must be reversed.

If a particle of mass m flies into the field perpendicular to the lines of induction, then it will move in a circle, and the Lorentz force will play the role of a centripetal force. The radius of the circle and the period of revolution of a particle in a uniform magnetic field can be found by the formulas:

Interaction of currents

Let's consider two cases. First, current flows in a straight wire. The second is in a circular loop. As we know, current creates a magnetic field.

In the first case, the magnetic induction of a wire with current I on distance R from it is calculated by the formula:

Mu is the magnetic permeability of the substance, mu with index zero is the magnetic constant.

In the second case, the magnetic induction at the center of a circular loop with current is:

Also, when solving problems, the formula for the magnetic field inside the solenoid can be useful. - this is a coil, that is, a set of circular turns with current.

Let their number be N , and the length of the solenoil itself is l . Then the field inside the solenoid is calculated by the formula:

By the way! For our readers there is now a 10% discount on

Magnetic flux and EMF

If magnetic induction is a vector characteristic of a magnetic field, then magnetic flux – scalar, which is also one of the most important field characteristics. Let's imagine that we have some kind of frame or contour that has a certain area. The magnetic flux shows how many lines of force pass through a unit area, that is, it characterizes the intensity of the field. measured in Weberach (WB) and denoted F .

S - contour area, alpha is the angle between the normal (perpendicular) to the contour plane and the vector AT .

When changing the magnetic flux through the circuit, the circuit is induced EMF , equal to the rate of change of the magnetic flux through the circuit. By the way, you can read more about what electromotive force is in another of our articles.

In essence, the formula above is the formula for Faraday's law of electromagnetic induction. We remind you that the rate of change of any quantity is nothing but its derivative with respect to time.

The reverse is also true for magnetic flux and induction EMF. A change in the current in the circuit leads to a change in the magnetic field and, accordingly, to a change in the magnetic flux. In this case, an EMF of self-induction arises, which prevents a change in the current in the circuit. The magnetic flux that permeates the circuit with current is called its own magnetic flux, is proportional to the strength of the current in the circuit and is calculated by the formula:

L is a proportionality factor called inductance, which is measured in Henry (Gn) . Inductance is affected by the shape of the circuit and the properties of the medium. For coil length l and with the number of turns N inductance is calculated by the formula:

The formula for the EMF of self-induction:

Magnetic field energy

Electricity, nuclear energy, kinetic energy. Magnetic energy is one form of energy. In physical problems, it is most often necessary to calculate the energy of the coil's magnetic field. Magnetic energy coil with current I and inductance L is equal to:

Volumetric field energy density:

Of course, these are not all the basic formulas of the physics section. « electricity and magnetism » , however, they can often help in solving standard problems and calculations. If you come across a problem with an asterisk, and you just can’t find the key to it, simplify your life and contact the