The magnetic field acts on the currents circulating in the magnetic needle. These influences add up to the effect of the magnetic field on the needle as a whole.

2. Formulate Ampere's law. Write down its mathematical expression.

Ampere's law: the force with which the magnetic field acts on a segment of a conductor in current (placed in this field) is numerically equal to the product of the current strength, the magnitude of the magnetic induction vector, the length of the conductor segment and the sine of the angle between the direction of the force

current and magnetic induction vector.

3. How is the Ampere force oriented relative to the direction of the current and the magnetic induction vector?

These vector quantities make up the right-hand triplet of vectors.

4. How is the direction of the Ampere force determined? Formulate the left-hand rule.

The direction of the Ampere force is determined by the left hand rule: if you place your left palm so that the outstretched fingers indicate the direction of the current, and the magnetic field lines dig into the palm, then the extended thumb will indicate the direction of the Ampere force acting on the conductor.

5. What is the magnitude of the magnetic induction vector? In what units is magnetic induction measured?

The magnitude of the magnetic induction vector is a quantity numerically equal to the ratio of the maximum Ampere force acting on the conductor to the product of the current strength and the length of the conductor.

If the wire through which the current flows is in a magnetic field, then each of the current carriers is acted upon by an Ampere force

Ampere's law in vector form

Establishes that a current-carrying conductor placed in a uniform magnetic field of induction B is acted upon by force, proportional strength current and magnetic field induction

Directed perpendicular to the plane in which the vectors dl and B lie. To determine the direction strength, acting on a current-carrying conductor placed in a magnetic field, the left-hand rule applies.

To find the Ampere force for two infinite parallel conductors, the currents of which flow in the same direction and these conductors are located at a distance r, it is necessary:

An infinite conductor with current I1 at a point at a distance r creates a magnetic field with induction:

According to the Biot-Savart-Laplace law for direct current:

Now, using Ampere’s law, we find the force with which the first conductor acts on the second:

According to the gimlet rule, it is directed towards the first conductor (similarly for, which means that the conductors attract each other).

We integrate, taking into account only a conductor of unit length (limits l from 0 to 1) and the Ampere force is obtained:

In the formula we used:

Current value

Speed ​​of chaotic carrier movement

Speed ​​of ordered movement

The Ampere force is the force with which a magnetic field acts on a conductor carrying current placed in this field. The magnitude of this force can be determined using Ampere's law. This law defines an infinitesimal force for an infinitely small section of a conductor. This makes it possible to apply this law to conductors of various shapes.

Formula 1 - Ampere's Law

B induction of a magnetic field in which a current-carrying conductor is located

I current strength in the conductor

dl infinitesimal element of the length of a conductor carrying current

alpha the angle between the induction of the external magnetic field and the direction of the current in the conductor

The direction of Ampere's force is found according to the left-hand rule. The wording of this rule is as follows. When the left hand is positioned in such a way that the lines of magnetic induction of the external field enter the palm, and four extended fingers indicate the direction of current movement in the conductor, while the thumb bent at a right angle will indicate the direction of the force that acts on the conductor element.

Figure 1 - left hand rule

Some problems arise when using the left-hand rule if the angle between the field induction and the current is small. It is difficult to determine where the open palm should be. Therefore, to simplify the application of this rule, you can position your palm so that it includes not the magnetic induction vector itself, but its module.

From Ampere's law it follows that Ampere's force will be equal to zero if the angle between the line of magnetic induction of the field and the current is equal to zero. That is, the conductor will be located along such a line. And the Ampere force will have the maximum possible value for this system if the angle is 90 degrees. That is, the current will be perpendicular to the magnetic induction line.

Using Ampere's law, you can find the force acting in a system of two conductors. Let's imagine two infinitely long conductors that are located at a distance from each other. Currents flow through these conductors. The force acting from the field created by conductor with current number one on conductor number two can be represented as:

Formula 2 - Ampere force for two parallel conductors.

The force exerted by conductor number one on the second conductor will have the same form. Moreover, if currents in conductors flow in one direction, then the conductor will be attracted. If in opposite directions, then they will repel each other. There is some confusion, because the currents flow in one direction, so how can they attract each other? After all, like poles and charges have always repelled. Or Amper decided that there was no point in imitating the others and came up with something new.

In fact, Ampere did not invent anything, since if you think about it, the fields created by parallel conductors are directed counter to each other. And why they are attracted, the question no longer arises. To determine in which direction the field created by the conductor is directed, you can use the right-hand screw rule.

Figure 2 - Parallel conductors with current

Using parallel conductors and the Ampere force expression for them, the unit of one Ampere can be determined. If identical currents of one ampere flow through infinitely long parallel conductors located at a distance of one meter, then the interaction force between them will be 2 * 10-7 Newton for each meter of length. Using this relationship, we can express what one Ampere will be equal to.

This video shows how a constant magnetic field created by a horseshoe magnet affects a current-carrying conductor. The role of the current-carrying conductor in this case is performed by an aluminum cylinder. This cylinder rests on copper bars through which electric current is supplied to it. The force acting on a current-carrying conductor in a magnetic field is called the Ampere force. The direction of action of the Ampere force is determined using the left-hand rule.

Ampere's law shows the force with which a magnetic field acts on a conductor placed in it. This force is also called Ampere force.

Statement of the law: the force acting on a current-carrying conductor placed in a uniform magnetic field is proportional to the length of the conductor, the magnetic induction vector, the current strength and the sine of the angle between the magnetic induction vector and the conductor.

If the size of the conductor is arbitrary and the field is non-uniform, then the formula is as follows:

The direction of Ampere's force is determined by the left-hand rule.

Left hand rule: if you position your left hand so that the perpendicular component of the magnetic induction vector enters the palm, and four fingers are extended in the direction of the current in the conductor, then set back 90° the thumb will indicate the direction of the Ampere force.

MP of the driving charge. Effect of MF on a moving charge. Ampere and Lorentz forces.

Any conductor carrying current creates a magnetic field in the surrounding space. In this case, electric current is the ordered movement of electric charges. This means that we can assume that any charge moving in a vacuum or medium generates a magnetic field around itself. As a result of generalizing numerous experimental data, a law was established that determines the field B of a point charge Q moving with a constant non-relativistic speed v. This law is given by the formula

(1)

where r is the radius vector drawn from the charge Q to the observation point M (Fig. 1). According to (1), vector B is directed perpendicular to the plane in which the vectors v and r are located: its direction coincides with the direction of translational motion of the right screw as it rotates from v to r.

Fig.1

The magnitude of the magnetic induction vector (1) is found by the formula

(2)

where α is the angle between vectors v and r. Comparing the Biot-Savart-Laplace law and (1), we see that a moving charge is equivalent in its magnetic properties to a current element: Idl = Qv

Effect of MF on a moving charge.

It is known from experience that a magnetic field affects not only current-carrying conductors, but also individual charges that move in a magnetic field. The force that acts on an electric charge Q moving in a magnetic field with a speed v is called the Lorentz force and is given by the expression: F = Q where B is the induction of the magnetic field in which the charge is moving.

To determine the direction of the Lorentz force, we use the rule of the left hand: if the palm of the left hand is positioned so that vector B enters it, and four extended fingers are directed along vector v (for Q>0 the directions I and v coincide, for Q Fig. 1 shows mutual orientation of vectors v, B (the field is directed towards us, shown in the figure by dots) and F for a positive charge. If the charge is negative, then the force acts in the opposite direction.

The modulus of the Lorentz force, as is already known, is equal to F = QvB sin a; where α is the angle between v and B.

MF has no effect on a stationary electric charge. This makes the magnetic field significantly different from the electric one. A magnetic field acts only on charges moving in it.

Knowing the effect of the Lorentz force on the charge, one can find the magnitude and direction of vector B, and the formula for the Lorentz force can be applied to find the magnetic induction vector B.

Since the Lorentz force is always perpendicular to the speed of motion of a charged particle, this force can only change the direction of this speed, without changing its modulus. This means that the Lorentz force does no work.

If a moving electric charge, together with a magnetic field with induction B, is also acted upon by an electric field with intensity E, then the total resulting force F, which is applied to the charge, is equal to the vector sum of forces - the force acting from the electric field, and Lorentz forces: F = QE + Q

Ampere and Lorentz forces.

The force acting on a current-carrying conductor in a magnetic field is called the Ampere force.

The force of a uniform magnetic field on a current-carrying conductor is directly proportional to the current strength, the length of the conductor, the magnitude of the magnetic field induction vector, and the sine of the angle between the magnetic field induction vector and the conductor:

F = B.I.l. sin α - Ampere's law.

The force acting on a charged moving particle in a magnetic field is called the Lorentz force:

The phenomenon of electromagnetic induction. Faraday's law. Induction emf in moving conductors. Self-induction.

Faraday suggested that if there is a magnetic field around a current-carrying conductor, then it is natural to expect that the opposite phenomenon should also occur - the emergence of an electric current under the influence of a magnetic field. And so in 1831, Faraday published an article in which he reported the discovery of a new phenomenon - the phenomenon of electromagnetic induction.

Faraday's experiments were extremely simple. He connected a galvanometer G to the ends of a coil L and brought a magnet closer to it. The galvanometer needle deflected, recording the appearance of current in the circuit. Current flowed while the magnet moved. When the magnet moved away from the coil, the galvanometer noted the appearance of a current in the opposite direction. A similar result was observed if the magnet was replaced by a current-carrying coil or a closed current-carrying loop.

A moving magnet or current-carrying conductor creates an alternating magnetic field through the coil L. If they are stationary, the field they create is constant. If a conductor with alternating current is placed near a closed loop, then a current will also arise in the closed loop. Based on the analysis of experimental data, Faraday established that current in conducting circuits appears when the magnetic flux changes through the area limited by this circuit.

This current was called induction. Faraday's discovery was called the phenomenon of electromagnetic induction and later formed the basis for the operation of electric motors, generators, transformers and similar devices.

So, if the magnetic flux through a surface bounded by a certain circuit changes, then an electric current arises in the circuit. It is known that electric current in a conductor can only arise under the influence of external forces, i.e. in the presence of emf. In the case of induced current, the emf corresponding to external forces is called the electromotive force of electromagnetic induction εi.

E.m.f. electromagnetic induction in a circuit is proportional to the rate of change of magnetic flux Фm through the surface limited by this circuit:

where k is the proportionality coefficient. This e.m.f. does not depend on what caused the change in magnetic flux - either by moving the circuit in a constant magnetic field, or by changing the field itself.

So, the direction of the induction current is determined by Lenz’s rule: For any change in the magnetic flux through a surface bounded by a closed conducting circuit, an induction current arises in the latter in such a direction that its magnetic field counteracts the change in the magnetic flux.

A generalization of Faraday's law and Lenz's rule is the Faraday-Lenz law: The electromotive force of electromagnetic induction in a closed conducting circuit is numerically equal and opposite in sign to the rate of change of magnetic flux through a surface bounded by the circuit:

This expression represents the basic law of electromagnetic induction.

At a rate of change of magnetic flux of 1 Wb/s, an emf is induced in the circuit. at 1 V.

Let the circuit in which the emf is induced consist not of one, but of N turns, for example, it is a solenoid. A solenoid is a cylindrical current-carrying coil consisting of a large number of turns. Since the turns in the solenoid are connected in series, εi in this case will be equal to the sum of the emf induced in each of the turns separately:

The German physicist G. Helmholtz proved that the Faraday-Lenz law is a consequence of the law of conservation of energy. Let a closed conducting circuit be in a non-uniform magnetic field. If a current I flows in the circuit, then under the action of Ampere's forces the loose circuit will begin to move. The elementary work dA performed when moving the contour during the time dt will be

dA = IdФm,

where dФm is the change in magnetic flux through the circuit area over time dt. The work done by the current in time dt to overcome the electrical resistance R of the circuit is equal to I2Rdt. The total work of the current source during this time is equal to εIdt. According to the law of conservation of energy, the work of the current source is spent on the two named works, i.e.

εIdt = IdФm + I2Rdt.

Dividing both sides of the equality by Idt, we get

Consequently, when the magnetic flux associated with the circuit changes, an electromotive force of induction arises in the latter

Electromagnetic vibrations. Oscillatory circuit.

Electromagnetic oscillations are oscillations of such quantities as inductance, resistance, emf, charge, current.

An oscillatory circuit is an electrical circuit that consists of a capacitor, a coil and a resistor connected in series. The change in electric charge on the capacitor plate over time is described by the differential equation:

Electromagnetic waves and their properties.

In the oscillatory circuit, the process of converting the electrical energy of the capacitor into the energy of the magnetic field of the coil and vice versa occurs. If at certain points in time we compensate for the energy losses in the circuit due to resistance due to an external source, we will obtain undamped electrical oscillations, which can be radiated into the surrounding space through the antenna.

The process of propagation of electromagnetic oscillations, periodic changes in the strength of electric and magnetic fields, in the surrounding space is called an electromagnetic wave.

Electromagnetic waves cover a wide range of wavelengths from 105 to 10 m and frequencies from 104 to 1024 Hz. By name, electromagnetic waves are divided into radio waves, infrared, visible and ultraviolet radiation, x-rays and -radiation. Depending on the wavelength or frequency, the properties of electromagnetic waves change, which is convincing evidence of the dialectical-materialistic law of the transition of quantity into a new quality.

The electromagnetic field is material and has energy, momentum, mass, moves in space: in a vacuum with a speed C, and in a medium with a speed: V=, where = 8.85;

Volumetric energy density of the electromagnetic field. The practical use of electromagnetic phenomena is very wide. These are systems and means of communication, radio broadcasting, television, electronic computer technology, control systems for various purposes, measuring and medical instruments, household electrical and radio equipment and others, i.e. something without which it is impossible to imagine modern society.

There is almost no exact scientific data on how powerful electromagnetic radiation affects people’s health, there are only unconfirmed hypotheses and, in general, not unfounded fears that everything unnatural has a destructive effect. It has been proven that ultraviolet, x-ray and high-intensity radiation in many cases cause real harm to all living things.

Geometric optics. Civil law laws.

Geometric (beam) optics uses an idealized idea of ​​a light ray - an infinitely thin beam of light propagating rectilinearly in a homogeneous isotropic medium, as well as the idea of ​​a point source of radiation shining uniformly in all directions. λ – light wavelength, – characteristic size

an object in the path of the wave. Geometric optics is a limiting case of wave optics and its principles are satisfied subject to the following conditions:

Geometric optics is also based on the principle of independence of light rays: the rays do not disturb each other when moving. Therefore, the movements of the rays do not prevent each of them from propagating independently of each other.

For many practical problems in optics, one can ignore the wave properties of light and consider the propagation of light to be rectilinear. In this case, the picture comes down to considering the geometry of the path of light rays.

Basic laws of geometric optics.

Let us list the basic laws of optics that follow from experimental data:

1) Straight-line propagation.

2) The law of independence of light rays, that is, two rays, intersecting, do not interfere with each other. This law agrees better with the wave theory, since particles could, in principle, collide with each other.

3) Law of reflection. the incident ray, the reflected ray and the perpendicular to the interface, reconstructed at the point of incidence of the ray, lie in the same plane, called the plane of incidence; the angle of incidence is equal to the angle

Reflections.

4) The law of light refraction.

Law of refraction: the incident ray, the refracted ray and the perpendicular to the interface, reconstructed from the point of incidence of the ray, lie in the same plane - the plane of incidence. The ratio of the sine of the angle of incidence to the sine of the angle of reflection is equal to the ratio of the speeds of light in both media.

Sin i1/ sin i2 = n2/n1 = n21

where is the relative refractive index of the second medium relative to the first medium. n21

If substance 1 is emptiness, vacuum, then n12 → n2 is the absolute refractive index of substance 2. It can be easily shown that n12 = n2 /n1, in this equality on the left is the relative refractive index of two substances (for example, 1 is air, 2 is glass) , and on the right is the ratio of their absolute refractive indices.

5) The law of reversibility of light (it can be derived from law 4). If you send light in the opposite direction, it will follow the same path.

From law 4) it follows that if n2 > n1, then Sin i1 > Sin i2. Let now we have n2< n1 , то есть свет из стекла, например, выходит в воздух, и мы постепенно увеличиваем угол i1.

Then we can understand that when a certain value of this angle (i1)pr is reached, it turns out that the angle i2 will be equal to π /2 (ray 5). Then Sin i2 = 1 and n1 Sin (i1)pr = n2 . So Sin

What is ampere power

In 1820, the outstanding French physicist Andre Marie Ampere (the unit of measurement of electric current is named after him) formulated one of the fundamental laws of all electrical engineering. Subsequently, this law was given the name ampere power.

As is known, when an electric current passes through a conductor, its own (secondary) magnetic field arises around it, the tension lines of which form a kind of rotating shell. The direction of these lines of magnetic induction is determined using the right hand rule (the second name is the “gimlet rule”): we mentally clasp the conductor with our right hand so that the flow of charged particles coincides with the direction indicated by the bent thumb. As a result, the other four fingers gripping the wire will point to the rotation of the field.

If two such conductors (thin wires) are placed in parallel, then the interaction of their magnetic fields will be affected by the ampere force. Depending on the direction of current in each conductor, they can repel or attract. When currents flow in one direction, the ampere force has an attractive effect on them. Accordingly, the opposite direction of currents causes repulsion. This is not surprising: although like charges repel, in this example it is not the charges themselves that interact, but magnetic fields. Since the direction of their rotation is the same, the resulting field is a vector sum, not a difference.

In other words, the magnetic field acts in a certain way on the conductor crossing the tension lines. The ampere strength (arbitrary conductor shape) is determined from the law formula:

where - I is the value of the current in the conductor; B - induction of the magnetic field in which the current-conducting material is placed; L - taken to calculate the length of the conductor with current (moreover, in this case it is assumed that the length of the conductor and the force tend to zero); alpha (a) - vector angle between the direction of movement of charged elementary particles and the lines of external field strength. The consequence is the following: when the angle between the vectors is 90 degrees, its sin = 1, and the value of the force is maximum.

The vector direction of action of the ampere force is determined using the rule of the left hand: we mentally place the palm of the left hand in such a way that the lines (vectors) of the magnetic induction of the external field enter the open palm, and the other four straightened fingers indicate the direction in which the current moves in the conductor. Then the thumb, bent at an angle of 90 degrees, will show the direction of the force acting on the conductor. If the angle between the electric current vector and an arbitrary induction line is too small, then to simplify the application of the rule, it is not the induction vector itself that should enter the palm, but the module.

The use of ampere power made it possible to create electric motors. We are all accustomed to the fact that it is enough to flip the switch of an electrical household appliance equipped with a motor for its actuator to come into action. And no one really thinks about the processes that occur during this process. The direction of the ampere force not only explains how the motors operate, but also allows you to determine exactly where the torque will be directed.

For example, let's imagine a DC motor: its armature is a base frame with a winding. The external magnetic field is created by special poles. Since the winding wound around the armature is circular, on opposite sides the direction of the current in the sections of the conductor is counter-current. Consequently, the action vectors of the ampere force are also counter-current. Since the armature is mounted on bearings, the mutual action of the ampere force vectors creates a torque. As the effective value of the current increases, the strength also increases. That is why the rated electric current (indicated in the passport for electrical equipment) and torque are directly interrelated. The increase in current is limited by design features: the cross-section of the wire used for winding, the number of turns, etc.

Ampere power

– Ampere's force (or Ampere's law)

The direction of the Ampere force is found according to the vector product rule - according to the rule of the left hand: place the four outstretched fingers of the left hand in the direction of the current, the vector enters the palm, the thumb bent at a right angle will show the direction of the force acting on the conductor with the current. (You can also determine the direction using your right hand: rotate the four fingers of your right hand from the first factor to the second, the thumb will indicate the direction.)

Ampere power module

,

where α is the angle between the vectors and .

If the field is uniform and the current-carrying conductor is of finite dimensions, then

At perpendicular

1. Determination of the unit of current measurement.

Any conductor carrying current creates a magnetic field around itself. If you place another conductor with current in this field, then interaction forces arise between these conductors. In this case, parallel co-directed currents attract, and oppositely directed currents repel.

Consider two infinitely long parallel conductors carrying currents I 1 And I 2, located in a vacuum at a distance d(for vacuum µ = 1). According to Ampere's law

The forward current magnetic field is equal to

,

force acting per unit length of conductor

The force acting per unit length of a conductor between two infinitely long current-carrying conductors is directly proportional to the current strength in each of the conductors and inversely proportional to the distance between them.

Definition of the unit of current measurement - Ampere:

The unit of current in the SI system is such a direct current that, flowing through two infinitely long parallel conductors of infinitely small cross-section, located in a vacuum at a distance of 1 m from each other, causes a force acting per unit length of the conductor equal to 2 10- 7 N.

µ = 1; I 1 = I 2 = 1 A; d=1 m; µ 0 = 4π·10-7 H/m – magnetic constant.

/ fizika / Ampere's law. Interaction of parallel currents

Ampere's law. Interaction of parallel currents.

Ampere's law is the law of interaction of direct currents. Established by Andre Marie Ampere in 1820. From Ampere's law it follows that parallel conductors with direct currents flowing in one direction attract, and in the opposite direction they repel. Ampere's law is also the law that determines the force with which a magnetic field acts on a small segment of a conductor carrying current. The force with which the magnetic field acts on the volume element dV of a conductor with current density located in a magnetic field with induction.

Topic 10. FORCES ACTING ON MOVING CHARGES IN A MAGNETIC FIELD.

10.1. Ampere's law.

10.3. The effect of a magnetic field on a current-carrying frame. 10.4. Units of measurement of magnetic quantities. 10.5. Lorentz force.

10.6. Hall effect.

10.7. Circulation of the magnetic induction vector.

10.8. Magnetic field of the solenoid.

10.9. Magnetic field of a toroid.

10.10. The work of moving a current-carrying conductor in a magnetic field.

10.1. Ampere's law.

In 1820, A. M. Amper experimentally established that two current-carrying conductors interact with each other with force:

	F = k	I 1 I 2

where b is the distance between the conductors, and k is the proportionality coefficient depending on the system of units.

The original expression of Ampere's law did not include any quantity characterizing the magnetic field. Then we figured out that the interaction of currents occurs through a magnetic field and therefore the law should include the characteristic of the magnetic field.

In modern SI notation, Ampere's law is expressed by the formula:

If the magnetic field is uniform and the conductor is perpendicular to the magnetic field lines, then

where I = qnυ dr S – current through a conductor with cross section S.

The direction of the force F is determined by the direction of the vector product or the left-hand rule (which is the same thing). We orient the fingers in the direction of the first vector, the second vector should enter the palm and the thumb shows the direction of the vector product.

Ampere's law is the first discovery of fundamental forces that depend on speeds. Power depends on movement! This have not happened before.

10.2. Interaction of two parallel infinite conductors with current.

Let b be the distance between the conductors. The problem should be solved this way: one of the conductors I 2 creates a magnetic field, the second I 1 is in this field.

Magnetic induction created by current I 2 at a distance b from it:

B 2 = µ 2 0 π I b 2 (10.2.1)

If I 1 and I 2 lie in the same plane, then the angle between B 2 and I 1 is straight, therefore

sin (l , B ) = 1 then, the force acting on the current element I 1 dl
F21 = B2 I1 dl =				µ0 I1 I2 dl
				2 πb
For each unit of length of the conductor there is a force
F 21 units =						I1 I2

(of course, from the side of the first conductor, exactly the same force acts on the second). The resulting force is equal to one of these forces! If these two conductors are

influence the third, then their magnetic fields B 1 and B 2 need to be added vectorially.

10.3. The effect of a magnetic field on a current-carrying frame.

The frame with current I is in a uniform magnetic field B, α is the angle between n and B (the direction of the normal is related to the direction of the current by the gimlet rule).

The Ampere force acting on the side of a frame of length l is equal to:

F1 = IlB (B l ).

The same force acts on the other side of length l. The result is a “couple of forces” or “torque.”

M = F1 h = IlB bsinα,

where arm h = bsinα. Since lb = S is the area of ​​the frame, then we can write

M = IBS sinα = Pm sinα.

This is where we wrote the expression for magnetic induction:

where M is the torque of the force, P is the magnetic moment.

The physical meaning of magnetic induction B is a value numerically equal to the force with which the magnetic field acts on a conductor of unit length along which it flows.

unit current. B = I F l ; Induction dimension [B] = A N m. .

So, under the influence of this torque the frame will rotate so that n r || B. The sides of length b are also affected by the Ampere force F 2 - it stretches the frame and so on

since the forces are equal in magnitude and opposite in direction, the frame does not move, in this case M = 0, a state of stable equilibrium

When n and B are antiparallel, M = 0 (since the arm is zero), this is a state of unstable equilibrium. The frame shrinks and, if it moves a little, it immediately appears

torque such that it will turn so that n r || B (Fig. 10.4).

In an inhomogeneous field, the frame will rotate and extend into an area of ​​stronger field.

10.4. Units of measurement of magnetic quantities.

As you might guess, it is Ampere's law that is used to establish the unit of current - the Ampere.

So, Ampere is a current of constant magnitude, which, passing through two parallel straight conductors of infinite length and negligibly small cross-section, located at a distance of one meter, one from the other in a vacuum

causes a force of 2 10 − 7 N m between these conductors.

I1 I2

where dl = 1 m; b = 1 m; I1

I2 = 1 A;

2 10− 7

Let us determine from here the dimension and value of µ 0:

In SI: 2·10

µ0 = 4π·10

or µ0 = 4π·10

–7 Gn

In GHS: µ 0 = 1

Bio-Savara-Laplace,

rectilinear

current carrying conductor

µ0 I

You can find the dimension of the magnetic field induction:

4 πb

1 T

One Tesla 1 T = 104 Gauss.

Gauss is a unit of measurement in the Gaussian system of units (GUS).

1 T (one tesla is equal to the magnetic induction of a uniform magnetic field in which) a torque of 1 Nm acts on a flat circuit with a current having a magnetic moment of 1 A m2.

The unit of measurement B is named after the Serbian scientist Nikola Tesla (1856 - 1943), who had a huge number of inventions.

Another definition: 1 T is equal to the magnetic induction at which the magnetic flux through an area of ​​1 m2 perpendicular to the direction of the field is 1 Wb.

The unit of measurement of magnetic flux Wb, got its name in honor of the German physicist Wilhelm Weber (1804 - 1891), a professor at universities in Halle, Göttingham, and Leipzig.

As we already said, magnetic flux Ф, through the surface S - one of the characteristics of the magnetic field (Fig. 10.5)