How to determine the direction of current using the gimlet rule. A magnetic field

Having entered adulthood, few people remember school course physics. However, sometimes it is necessary to delve into your memory, because some knowledge acquired in your youth can greatly facilitate the memorization of complex laws. One of these is the right and left hand rule in physics. Using it in life allows you to understand complex concepts (for example, 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 the common man who graduated long ago and forgot unnecessary (as it seemed to him) information.

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Formulation of the gimlet rule

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

Gimlet rule (rule right hand) – this name is not related to the name of the physicist who formulated it. The name is more based on a tool that has a certain direction of the screw. Usually a gimlet (screw, corkscrew) has a so-called The thread is right-handed, the drill enters the ground clockwise. Let us consider the application of this statement to determine magnetic field.

You need to clench your right hand into a fist, raising your thumb up. Now let's loosen the other four a little. They are the ones who tell 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

Considering the application of this law, let's start with the right-hand rule. If the direction of the magnetic field vector is known, using a gimlet you can do without knowing the law electromagnetic induction. Let's 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 us pay attention to a permanent controlled magnet, an analogue of which is a solenoid. At its core, it is a coil with two contacts. It is known that current moves from “+” to “-”. Based on this information, we take the solenoid in our right hand in such a position that 4 fingers indicate the direction of current flow. Then the extended thumb will indicate the vector of the magnetic field.

Left hand rule: what can be determined by using it

Do not confuse the rules of the left hand and the gimlet - they are intended for completely different purposes. With the help of your left hand you can determine two forces, or rather, their direction. This:

Lorentz force;
Ampere power.

Let's try to figure out how it works.

Left hand rule for Ampere force: what is it?

Place your left hand along the conductor so that your fingers are directed in the direction the current flows. The thumb will point in the direction of the Ampere force vector, and the magnetic field vector will be directed in the direction of the hand, between the thumb and index finger. This will be the left-hand rule for ampere power, the formula of which looks like this:

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

We position 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) will indicate the direction of the magnetic field (from the north pole to the south), and the middle finger, located perpendicularly away from the thumb, will indicate the direction of the current in the conductor.

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

Conclusion

Once you understand the rules of the right and left hands, the dear reader will understand how easy it is to use them. After all, they replace 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 valued readers. If you have any questions, you can leave them in the discussions below. The site editors will be happy to answer them as quickly 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.

Instructions

Read in the eighth grade textbook what the rules of the right propeller sound like. This rule otherwise it is also called the gimlet rule or the right-hand rule, which indicates its semantic nature. So, one of the formulations of the rule of the right screw states that in order to understand the direction of the magnetic field located around a conductor with current, it is necessary to imagine that the translational motion of some 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 conductor carrying current.

Please note that the formulation and understanding of this rule becomes clearer if you 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, solenoid. As you know, it is an inductor coil 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 diagram of the solenoid on a piece of paper from 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 by the direction of the current where the magnetic field lines are directed. In this case, they can be directed either from you or towards you.

Imagine that you are tightening a screw or screw, rotating it in the direction of current flow in the solenoid. The forward movement of the screw indicates the direction of the magnetic field inside the solenoid. If the direction of the current is clockwise, then the magnetic field induction vector is directed away from you.

If you are not comfortable applying abstract rules using a gimlet handle or a screw to every problem, use the right-hand screw rule in the right-hand rule formulation. The effect of this rule is the same, only the method of determining the direction of induction of the magnetic field or current in the coil is different.

Draw the end of the solenoid again. Show the direction of current in the coil (counterclockwise). Place the right edge of your right hand on the drawn circle so that the little finger is in contact with the circle and four fingers point in the direction of the current in the conductors. Place your thumb 90 degrees, its direction in your direction coincides with the direction of the magnetic field in the solenoid.

In physics and electrical engineering, various techniques and methods are widely used to determine one of the characteristics of a magnetic field - the direction of intensity. For this purpose, the law of the gimlet, right and left hands is used. These methods allow you to obtain fairly accurate results.

Gimlet and right hand rule

The gimlet's law is used to determine the direction of magnetic field strength. It works under the condition that the magnetic field is located in a straight line relative to the current-carrying conductor.

This rule consists in the coincidence of the direction of the magnetic field with the direction of the handle of the gimlet, provided that the gimlet is screwed in with a right-hand thread in the direction of the electric current. This rule also applies to solenoids. In this case, the thumb extended on the right hand indicates the direction of the lines. In this case, the solenoid is grasped so that the fingers indicate the direction of the current in its turns. A prerequisite is that the length of the coil exceeds its diameter.

The right hand rule is the opposite of the gimlet rule. When grasping the element under study, the fingers in a clenched fist indicate the direction magnetic lines. At the same time, it is taken into account forward movement in the direction of the magnetic lines. The thumb, which is bent 90 degrees relative to the palm, indicates the direction.

When the conductor moves, the lines of force enter perpendicularly into the palm. The thumb is extended perpendicularly and indicates the direction of movement of the conductor. The remaining four protruding fingers are located in the direction of the induction current.

Left hand rule

Among such methods, as a rule, the gimlet, right and left hands, the left hand rule should be noted. In order for this rule to work, it is necessary to position the left palm in such a way that the direction of the four fingers is towards the electric current in the conductor. The induction lines enter the palm perpendicularly at an angle of 90 0. The thumb is bent and indicates the direction of the force acting on the conductor. Typically, this law is applied when it is necessary to determine the direction of deflection of a conductor. In this situation, a conductor is located between two magnets and an electric current is passed through it.

The left hand rule is also formulated in such a way that the four fingers on the left hand are located in the direction in which positive or negative particles of electric current move. The induction lines, as in other cases, should be perpendicular to the palm and enter into it. The protruding thumb indicates the direction of the Ampere or Lorentz force.

The rule of gimlet, right hand and left hand is widely used in physics. Mnemonic rules are needed for easy and intuitive memorization of information. Usually this is the application of complex quantities and concepts to everyday and improvised things. The first person to formulate these rules is physicist Peter Buravchik. This rule refers to the mnemonic and is closely related to the right-hand rule; its task is to determine the direction of the axial vectors with a known direction of the base one. That's what the encyclopedias say, but we'll tell you about it in simple words, short and clear.

Explanation of the name

Most people remember mention of this from a physics course, namely the electrodynamics section. This happened for a reason, because this mnemonic is often given to students to simplify their understanding of the material. In fact, the gimlet rule is used both in electricity, to determine the direction of the magnetic field, and in other sections, for example, to determine angular velocity.

A gimlet is a tool for drilling small diameter holes in soft materials, for modern man It would be more common to use a corkscrew as an example.

Important! It is assumed that the gimlet, screw or corkscrew has a right-hand thread, that is, the direction of its rotation when tightened is clockwise, i.e. to the right.

The video below provides the full formulation of the gimlet rule, be sure to watch it to understand the whole point:

How is the magnetic field related to the gimlet and hands?

In physics problems, when studying electrical quantities, one is often faced with the need to find the direction of the current from the magnetic induction vector and vice versa. These skills will also be required when solving complex tasks and calculations of systems connected by a magnetic field.

Before we begin to consider the rules, I want to remind you that current flows from a point with a higher potential to a point with a lower one. To put it simply, current flows from plus to minus.

The gimlet rule has the following meaning: when the tip of the gimlet is screwed in along the direction of the current, the handle will rotate in the direction of vector B (the vector of magnetic induction lines).

The right hand rule works like this:

Place your thumb as if you were showing “cool!”, then turn your hand so that the direction of the current and the finger coincide. Then the remaining four fingers will coincide with the magnetic field vector.

A visual analysis of the right hand rule:

To see this more clearly, conduct an experiment - scatter metal shavings on paper, make a hole in the sheet and thread a wire, after applying current to it, you will see that the shavings will group into concentric circles.

Magnetic field in a solenoid

All of the above is true for a straight conductor, but what if the conductor is wound into a coil?

We already know that when current flows around a conductor, a magnetic field is created, a coil is a wire coiled into rings around a core or mandrel many times. The magnetic field in this case increases. The solenoid and the coil are, in principle, the same thing. main feature is that the magnetic field lines run the same way as in the situation with a permanent magnet. The solenoid is a controlled analogue of the latter.

The right hand rule for the solenoid (coil) will help us determine the direction of the magnetic field. If you hold the coil in your hand with four fingers facing in the direction the current is flowing, then your thumb will point to vector B in the middle of the coil.

If you twist a gimlet along the turns, again in the direction of the current, i.e. from the “+” terminal to the “-” terminal of the solenoid, then the sharp end and the direction of movement correspond to the magnetic induction vector.

In simple words, wherever you twist the gimlet, the magnetic field lines come out. The same is true for one turn (circular conductor)

Determining the direction of current with a gimlet

If you know the direction of vector B - magnetic induction, you can easily apply this rule. Mentally move the gimlet along the direction of the field in the coil with the sharp part forward, respectively, clockwise rotation along the axis of movement will show where the current flows.

If the conductor is straight, rotate the corkscrew handle along the indicated vector, so that this movement is clockwise. Knowing that it has a right-hand thread - the direction in which it is screwed in coincides with the current.

What is connected with the left hand

Do not confuse the gimlet and the left hand rule; it is needed to determine the force acting on the conductor. The straightened palm of the left hand is located along the conductor. The fingers point in the direction of the flow of current I. Field lines pass through the open palm. The thumb coincides with the force vector - this is the meaning of the left hand rule. This force is called the Ampere force.

You can apply this rule to an individual charged particle and determine the direction of the 2 forces:

Lorenz.
Ampere.

Imagine that a positively charged particle is moving in a magnetic field. The lines of the magnetic induction vector are perpendicular to the direction of its movement. You need to place your open left palm with your fingers in the direction of the movement of the charge, vector B should penetrate the palm, then the thumb will indicate the direction of vector Fa. If the particle is negative, the fingers point against the direction of the charge.

If any point was unclear to you, the video clearly shows how to use the left-hand rule:

It is important to know! If you have a body and there is a force acting on it that tends to turn it, turn the screw in that direction and you will determine where the moment of force is directed. If we are talking about angular velocity, then the situation here is like this: when the corkscrew rotates in the same direction as the rotation of the body, it will screw in the direction of the angular velocity.

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 are lined 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 magnetic field lines of the 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 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. Electricity represents the directed movement of charged particles, so a magnetic field acts on a conductor carrying current.

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

For determining magnetic poles current coils are 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.

Bibliography