Left hand rule for current coil. left hand rule
The first step will focus on the right hand rule. With it, you can determine the direction of the magnetic lines of a current-carrying conductor. To do this, we need to know the direction of the current in the conductor. Just look at the battery or accumulator poles. Since the current is directed from “+” to “-”, it will go from the side of the conductor connected to + to the side of -. Now that we have learned the direction of the current, we need to “take”) the right hand and bend all the fingers into the palm, except for the thumb! As in the picture. Now we need to “grasp” the conductor, but in such a way that thumb showed the direction of the current i.e. was directed where the current was). With this arrangement of the hand, the fingers bent around the conductor will indicate the direction of the lines of its magnetic field)
2 step
Clear?)
Now let's move on to determining the poles of a coil with current. We must again determine the direction of the current in a similar way. After that, we do almost the same thing, only we leave the fingers more straight, but bent. We approach our coil and direct our fingers (everything except for the protruding large one) in the direction of the current in it, that is, our fingers have become, as it were, not whole turns of the coil). In this case, the thumb shows the direction to the north pole of the coil.
P.S. A small digression) the finger also shows the direction of the magnetic lines PASSING THROUGH the coil, and vice versa - shows the direction OPPOSITE to the lines passing outside the coil and "entering its south pole.
3 step
Let's start understanding the rule of the LEFT hand. It makes it possible to determine the direction of the Ampere force acting on a conductor with current in a magnetic field of a permanent magnet! VO! =). For the experiment, we just need a straight left hand, but with the right finger bent 90 degrees. In a magnetic field, the hand must be positioned so that the north pole “looks” into the inner part of the palm, i.e. so that the lines of the magnetic field are directed to the hand. Under these conditions, we need straight fingers to point in the direction of the current in the CONDUCTOR. If everything is taken into account and done correctly, then the finger bent 90 degrees will show the direction of the Ampere force.
With the help of the gimlet rule, the directions of magnetic lines (they are also called magnetic induction lines) around a current-carrying conductor are determined.
Gimlet Rule: Definition
The rule itself sounds like this: when the direction of the gimlet moving forward coincides with the direction of the current in the conductor under study, the direction of rotation of the handle of this gimlet is the same as the direction of the magnetic field of the current.
It is also called the right hand rule, and in this context the definition is much clearer. If you grab the wire with your right hand so that four fingers are clenched into a fist, and the thumb points up (that is, as we usually show “class!” with our hand), then the thumb will indicate in which direction the current is moving, and the other four fingers – direction of magnetic field lines
A gimlet is a screw with a right-hand thread. They are the standard in technology, because they represent the vast majority. By the way, the same rule could be formulated on the example of the movement of the hour hand, because the right-handed screw is twisted in this direction.
Application of the gimlet rule
In physics, the gimlet rule is used not only to determine the direction of the magnetic field of the current. So, for example, it also applies to the calculation of the direction of axial vectors, the angular velocity vector, the magnetic induction vector B, the direction of the induction current with a known magnetic induction vector, and many other options. But for each such case, the rule has its own formulation.
So, for example, to calculate the product vector, it says: if you draw the vectors so that they coincide at the beginning, and move the first factor vector to the second factor vector, then the gimlet moving in the same way will screw in the direction of the product vector.
Or this is how the gimlet rule for mechanical rotation of speed will sound: if you rotate the screw in the same direction in which the body rotates, it will screw in the direction of the angular velocity.
This is how the gimlet rule for the moment of forces looks like: when the screw rotates in the same direction in which the forces turn the body, the gimlet will screw in the direction of these forces.
GIM RULE for a straight conductor with current
Serves to determine the direction of magnetic lines (lines of magnetic induction)
around a straight current-carrying conductor.
If the direction of the translational movement of the gimlet coincides with the direction of the current in the conductor, then the direction of rotation of the gimlet handle coincides with the direction of the lines of the magnetic field of the current.
Suppose a conductor with current is located perpendicular to the plane of the sheet:
1. email direction current from us (to the sheet plane)
According to the gimlet rule, magnetic field lines will be directed clockwise.
Then, according to the gimlet rule, the magnetic field lines will be directed counterclockwise.
RIGHT HAND RULE for solenoid, i.e. coils with current
Serves to determine the direction of magnetic lines (lines of magnetic induction) inside the solenoid.
If you grasp the solenoid with the palm of your right hand so that four fingers are directed along the current in the turns, then the thumb set aside will show the direction of the magnetic field lines inside the solenoid.
1. How do 2 coils interact with each other with current? 
2. How are the currents in the wires directed if the interaction forces are directed as in the figure?
3. Two conductors are parallel to each other. Indicate the direction of current in the LED conductor.
Looking forward to the next lesson on "5"!
INTERESTING
It is known that superconductors (substances that have almost zero electrical resistance at certain temperatures) can create very strong magnetic fields. Experiments have been made to demonstrate such magnetic fields. After cooling the ceramic superconductor with liquid nitrogen, a small magnet was placed on its surface. The repulsive force of the magnetic field of the superconductor was so high that the magnet rose, hovered in the air and hovered over the superconductor until the superconductor, when heated, lost its extraordinary properties.
Much has been done since the invention of electricity. scientific work in physics to study its characteristics, features and influence on environment. The gimlet's 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 inductor, 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 own 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:
- A permanent magnet, a "reversible" conductor, an electrically charged moving particle have an EM region around them;
- A charged particle moving in this region is subject to some influence from the EM background;
- 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 largest. 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 construction of electric motors is based on the Ampère forces in general and the left hand rule in particular.
Video
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 current-carrying conductor (see Fig. 1). This proved the magnetic effect of the current. After conducting several experiments, Oersted found that the rotation of the magnetic needle depended on the direction of the current in the conductor.
Rice. 1. Oersted's experience
In order to imagine by what principle the magnetic needle rotates near a current-carrying conductor, consider the view from the end of the conductor (see Fig. 2, the current is directed to the figure, - from the figure), near which the magnetic needles are installed. After passing the current, the arrows will line up in a certain way, opposite poles to each other. Since the magnetic arrows line up tangentially to the magnetic lines, the magnetic lines of a direct conductor with current are circles, and their direction depends on the direction of the current in the conductor.
Rice. 2. The location of the magnetic arrows near a direct conductor with current
For a more visual demonstration of the magnetic lines of a conductor with current, the following experiment can be carried out. If iron filings are poured around a conductor with current, then after a while the filings, having fallen into the magnetic field of the conductor, will be magnetized and located in circles that cover the conductor (see Fig. 3).
Rice. 3. The location of the iron filings around the conductor with current ()
To determine the direction of magnetic lines near a conductor with current, there is gimlet rule(rule of the right screw) - if you screw the 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 of the magnetic field 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 lines of the magnetic field 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 the current along the direction of the magnetic field lines.
After the discovery of the phenomenon of the appearance of a magnetic field near a conductor with current, Oersted sent the results of his research to most of the leading scientists in Europe. Having received these data, the French mathematician and physicist Ampère began his series of experiments and after a while demonstrated to the public the experience of the interaction of two parallel conductors with current. Ampere established that if two parallel conductors flow in one direction, then such conductors attract (see Fig. 6 b) if the current flows in opposite directions, the conductors repel (see Fig. 6 a).
Rice. 6. Ampere experience ()
Ampère drew the following conclusions from his experiments:
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 a directed movement of charged particles, so the 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
Along the sides of the rectangle (conductive frame) we screw an imaginary gimlet in the direction of the current.
Near the right side of the frame, the 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 as 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 needles 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 coil with current, and also that the solenoid has magnetic poles. If you change the direction of the current in the coil, the magnetic needles will turn around.
Rice. 9. Ampère's experience. The formation of a magnetic field near a coil with current
To determine the magnetic poles of a coil with current, right hand rule for solenoid(see Fig. 10) - if you grasp the solenoid with the palm of your right hand, pointing four fingers in the direction of the current in the turns, then the 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 solenoid with current
Determine the direction of the current in the coil and the poles at the current source if the magnetic poles indicated in Figure 11 occur during the passage of current in the coil.
Rice. 11. Illustration for the problem
Solution
According to the right hand rule for the solenoid, wrap around the coil so that the thumb points to its north pole. 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
In this lesson, we examined the phenomenon of the occurrence of a magnetic field near a direct current-carrying conductor and a current-carrying coil (solenoid). The rules for finding the magnetic lines of these fields were also studied.
Bibliography
- A.V. Peryshkin, E.M. Gutnik. Physics 9. - Bustard, 2006.
- G.N. Stepanova. Collection of problems in physics. - M.: Enlightenment, 2001.
- A. Fadeeva. Physics tests (grades 7 - 11). - M., 2002.
- V. Grigoriev, G. Myakishev Forces in nature. - M.: Nauka, 1997.
Homework
- Internet portal Clck.ru ().
- Internet portal Class-fizika.narod.ru ().
- Internet portal Festival.1september.ru ().