When the magnetic flux is zero. Basic formulas

1. The principle of active radar.
2. Pulse radar. Operating principle.
3. Basic time relationships of pulse radar operation.
4.Types of radar orientation.
5. Formation of a sweep on the PPI radar.
6. The principle of operation of the induction lag.
7.Types of absolute lags. Hydroacoustic Doppler log.
8.Flight data recorder. Description of work.
9. Purpose and operating principle of AIS.
10.Transmitted and received AIS information.
11.Organization of radio communications in AIS.
12.Composition of shipboard AIS equipment.
13. Structural diagram of the ship's AIS.
14. Operating principle of SNS GPS.
15.The essence of differential GPS mode.
16. Sources of errors in GNSS.
17. Block diagram of a GPS receiver.
18. Concept of ECDIS.
19.Classification of ENC.
20.Purpose and properties of the gyroscope.
21. The principle of operation of the gyrocompass.
22. The principle of operation of a magnetic compass.

Electronic thermometers are widely used as temperature meters. You can view contact and non-contact digital thermometers on the website http://mera-tek.ru/termometry/termometry-elektronnye. These devices mainly provide temperature measurement in technological installations due to high measurement accuracy and high recording speed.

Electronic potentiometers, both indicating and recording, use automatic current stabilization in the potentiometer circuit and continuous thermocouple compensation.

Connection of current-carrying conductors- part of the cable connection process. Multi-wire conductors with a cross-sectional area from 0.35 to 1.5 mm 2 are connected by soldering after twisting the individual wires (Fig. 1). If they are restored using insulating tubes 3, then before twisting the wires they must be put on the core and moved towards the cut of the sheath 4.

Rice. 1. Connection of cores by twisting: 1 - conductive core; 2 - core insulation; 3 — insulating tube; 4 - cable sheath; 5 - tinned wires; 6 - soldered surface

Solid wires They are overlapped, fastened before soldering with two bands of two or three turns of tinned copper wire with a diameter of 0.3 mm (Fig. 2). You can also use special wago 222 415 terminals, which have become very popular today due to their ease of use and reliability of operation.

When installing electrical actuators, their housing must be grounded with a wire with a cross-section of at least 4 mm 2 through a grounding screw. The connection point of the grounding conductor is thoroughly cleaned, and after connection, a layer of CIATIM-201 grease is applied to it to protect it from corrosion. Upon completion of installation, check the value, which should be at least 20 MOhm, and the grounding device, which should not exceed 10 Ohm.

Rice. 1. Electrical connection diagram of the sensor unit of a single-turn electrical mechanism. A - amplifier block BU-2, B - magnetic sensor block, B - electric actuator

Installation of the sensor unit of single-turn electrical actuators is carried out according to the electrical connection diagram shown in Fig. 1, with a wire with a cross-section of at least 0.75 mm 2. Before installing the sensor, it is necessary to check its functionality according to the diagram shown in Fig. 2.

21.03.2019

Types of gas analyzers

When using gas in furnaces, various devices and installations, it is necessary to control the combustion process to ensure safe operation and efficient operation of the equipment. In this case, the qualitative and quantitative composition of the gas environment is determined using instruments called

MAGNETIC FLUX

MAGNETIC FLUX(symbol F), a measure of the strength and extent of the MAGNETIC FIELD. The flux through area A at right angles to the same magnetic field is Ф = mHA, where m is the magnetic PERMEABILITY of the medium, and H is the intensity of the magnetic field. Magnetic flux density is the flux per unit area (symbol B), which is equal to N. A change in magnetic flux through an electrical conductor induces an ELECTRICAL MOTORIVE FORCE.

Scientific and technical encyclopedic dictionary.

See what "MAGNETIC FLUX" is in other dictionaries:

The flow of the magnetic induction vector B through any surface. The magnetic flux through a small area dS, within which the vector B is unchanged, is equal to dФ = ВndS, where Bn is the projection of the vector onto the normal to the area dS. Magnetic flux F through the final... ... Big Encyclopedic Dictionary

- (magnetic induction flux), flux F of the magnetic vector. induction B through k.l. surface. M. p. dФ through a small area dS, within the limits of which the vector B can be considered unchanged, is expressed by the product of the area size and the projection Bn of the vector onto ... ... Physical encyclopedia

magnetic flux- A scalar quantity equal to the flux of magnetic induction. [GOST R 52002 2003] magnetic flux The flux of magnetic induction through a surface perpendicular to the magnetic field, defined as the product of the magnetic induction at a given point by the area... ... Technical Translator's Guide

MAGNETIC FLUX- flux Ф of the magnetic induction vector (see (5)) B through the surface S normal to the vector B in a uniform magnetic field. SI unit of magnetic flux (cm) ... Big Polytechnic Encyclopedia

A value characterizing the magnetic effect on a given surface. The magnetic field is measured by the number of magnetic lines of force passing through a given surface. Technical railway dictionary. M.: State transport... ... Technical railway dictionary

Magnetic flux- a scalar quantity equal to the flux of magnetic induction... Source: ELECTRICAL ENGINEERING. TERMS AND DEFINITIONS OF BASIC CONCEPTS. GOST R 52002 2003 (approved by Resolution of the State Standard of the Russian Federation dated 01/09/2003 N 3 art.) ... Official terminology

The flow of the magnetic induction vector B through any surface. The magnetic flux through a small area dS, within which the vector B is unchanged, is equal to dФ = BndS, where Bn is the projection of the vector onto the normal to the area dS. Magnetic flux F through the final... ... Encyclopedic Dictionary

Classical electrodynamics ... Wikipedia

magnetic flux- , the flux of magnetic induction is the flux of the magnetic induction vector through any surface. For a closed surface, the total magnetic flux is zero, which reflects the solenoidal nature of the magnetic field, i.e. the absence in nature... Encyclopedic Dictionary of Metallurgy

Magnetic flux- 12. Magnetic flux Magnetic induction flux Source: GOST 19880 74: Electrical engineering. Basic concepts. Terms and definitions original document 12 magnetic on ... Dictionary-reference book of terms of normative and technical documentation

Books

, Mitkevich V.F.. This book contains a lot that is not always paid due attention when it comes to magnetic flux, and that has not yet been stated clearly enough or has not been...
Magnetic flux and its transformation, Mitkevich V.F.. This book will be produced in accordance with your order using Print-on-Demand technology. This book contains a lot that is not always given due attention when it comes to...

MAGNETIC FLUX- (magnetic induction flux), flux F of the magnetic vector. induction B through k.l. surface. M. p. dФ through a small area dS, within the limits of which the vector B can be considered unchanged, is expressed by the product of the area size and the projection Bn of the vector onto ... ... Physical encyclopedia

MAGNETIC FLUX- (symbol F), a measure of the strength and extent of the MAGNETIC FIELD. The flux through area A at right angles to the same magnetic field is Ф = mHA, where m is the magnetic PERMEABILITY of the medium, and H is the intensity of the magnetic field. Magnetic flux density is the flux... ... Scientific and technical encyclopedic dictionary

MAGNETIC FLUX- a value characterizing the magnetic effect on a given surface. The magnetic field is measured by the number of magnetic lines of force passing through a given surface. Technical railway dictionary. M.: State transport... ... Technical railway dictionary

magnetic flux- flux of magnetic induction vector B through any surface. The magnetic flux through a small area dS, within which the vector B is unchanged, is equal to dФ = BndS, where Bn is the projection of the vector onto the normal to the area dS. Magnetic flux F through the final... ... Encyclopedic Dictionary

Books

, Mitkevich V. F.. This book contains a lot that is not always paid due attention when it comes to magnetic flux, and that has not yet been stated clearly enough or has not been... Buy for 2252 UAH (Ukraine only)
Magnetic flux and its transformation, Mitkevich V.F.. This book will be produced in accordance with your order using Print-on-Demand technology. This book contains a lot that is not always given due attention when it comes to...

DEFINITION

Magnetic induction vector flux(or magnetic flux) (dФ) in the general case, through an elementary area a scalar physical quantity is called, which is equal to:

where is the angle between the direction of the magnetic induction vector () and the direction of the normal vector () to the area dS ().

Based on formula (1), the magnetic flux through an arbitrary surface S is calculated (in the general case) as:

The magnetic flux of a uniform magnetic field through a flat surface can be found as:

For a uniform field, a flat surface located perpendicular to the magnetic induction vector, the magnetic flux is equal to:

The flux of the magnetic induction vector can be negative and positive. This is due to the choice of a positive direction. Very often the flux of the magnetic induction vector is associated with the circuit through which the current flows. In this case, the positive direction of the normal to the contour is related to the direction of current flow by the right gimlet rule. Then, the magnetic flux that is created by the current-carrying circuit through the surface bounded by this circuit is always greater than zero.

The unit of magnetic flux in the International System of Units (SI) is the Weber (Wb). Formula (4) can be used to determine the unit of measurement of magnetic flux. One Weber is a magnetic flux that passes through a flat surface with an area of 1 square meter, placed perpendicular to the lines of force of a uniform magnetic field:

Gauss's theorem for magnetic field

Gauss's theorem for magnetic field flux reflects the fact that there are no magnetic charges, which is why magnetic induction lines are always closed or go to infinity; they have no beginning or end.

Gauss's theorem for magnetic flux is formulated as follows: Magnetic flux through any closed surface (S) is equal to zero. In mathematical form, this theorem is written as follows:

It turns out that Gauss's theorems for the fluxes of the magnetic induction vector () and the electrostatic field strength () through a closed surface differ fundamentally.

Examples of problem solving

EXAMPLE 1

Exercise

Calculate the flux of the magnetic induction vector through a solenoid that has N turns, core length l, cross-sectional area S, core magnetic permeability. The current flowing through the solenoid is equal to I.

Solution

Inside the solenoid, the magnetic field can be considered uniform. Magnetic induction can be easily found using the theorem on the circulation of the magnetic field and choosing a rectangular contour as a closed loop (circulation of the vector along which we will consider (L)) (it will cover all N turns). Then we write (we take into account that outside the solenoid the magnetic field is zero, in addition, where the contour L is perpendicular to the lines of magnetic induction B = 0):

In this case, the magnetic flux through one turn of the solenoid is equal to ():

The total flux of magnetic induction that goes through all turns:

Answer

EXAMPLE 2

Exercise	What will be the flux of magnetic induction through a square frame, which is located in a vacuum in the same plane with an infinitely long straight conductor with current (Fig. 1). The two sides of the frame are parallel to the wire. The length of the side of the frame is b, the distance from one of the sides of the frame is c.
Solution	The expression with which we can determine the magnetic field induction will be considered known (see Example 1 of the section “Magnetic induction unit of measurement”):

Magnetic induction vector flux IN (magnetic flux) through a small surface area dS called a scalar physical quantity equal to

Here , is the unit normal vector to the area dS, In n- vector projection IN to the normal direction, - the angle between the vectors IN And n (Fig. 6.28).

Rice. 6.28. Magnetic induction vector flux through the pad

Magnetic flux F B through an arbitrary closed surface S equals

The absence of magnetic charges in nature leads to the fact that the vector lines IN have neither beginning nor end. Therefore the vector flow IN through a closed surface must be equal to zero. Thus, for any magnetic field and an arbitrary closed surface S condition is met

Formula (6.28) expresses Ostrogradsky-Gauss theorem for vector :

Let us emphasize once again: this theorem is a mathematical expression of the fact that in nature there are no magnetic charges on which magnetic induction lines begin and end, as was the case in the case of electric field strength E point charges.

This property significantly distinguishes a magnetic field from an electric one. The lines of magnetic induction are closed, therefore the number of lines entering a certain volume of space is equal to the number of lines leaving this volume. If the incoming fluxes are taken with one sign, and the outgoing fluxes with another, then the total flux of the magnetic induction vector through the closed surface will be equal to zero.

Rice. 6.29. W. Weber (1804–1891) - German physicist

The difference between a magnetic field and an electrostatic one is also manifested in the value of the quantity we call circulation- integral of a vector field along a closed path. In electrostatics the integral is equal to zero

taken along an arbitrary closed contour. This is due to the potentiality of the electrostatic field, that is, to the fact that the work done to move a charge in an electrostatic field does not depend on the path, but only on the position of the starting and ending points.

Let's see how things stand with a similar value for the magnetic field. Let's take a closed loop covering direct current and calculate the vector circulation for it IN , that is

As was obtained above, the magnetic induction created by a straight conductor with current at a distance R from the conductor is equal to

Let us consider the case when the contour enclosing the direct current lies in a plane perpendicular to the current and is a circle with a radius R centered on the conductor. In this case, the circulation of the vector IN along this circle is equal

It can be shown that the result for the circulation of the magnetic induction vector does not change with continuous deformation of the circuit, if during this deformation the circuit does not intersect the current lines. Then, due to the principle of superposition, the circulation of the magnetic induction vector along a path covering several currents is proportional to their algebraic sum (Fig. 6.30)

Rice. 6.30. Closed loop (L) with a specified bypass direction.
The currents I 1, I 2 and I 3 are depicted, creating a magnetic field.
Only currents I 2 and I 3 contribute to the circulation of the magnetic field along the contour (L)

If the selected circuit does not cover currents, then the circulation through it is zero.

When calculating the algebraic sum of currents, the sign of the current should be taken into account: we will consider positive a current whose direction is related to the direction of traversal along the contour by the rule of the right screw. For example, the current contribution I 2 into the circulation is negative, and the current contribution I 3 - positive (Fig. 6.18). Using the ratio

between current strength I through any closed surface S and current density, for vector circulation IN can be written down

Where S- any closed surface resting on a given contour L.

Such fields are called vortex. Therefore, a potential cannot be introduced for a magnetic field, as was done for the electric field of point charges. The difference between the potential and vortex fields can be most clearly represented by the picture of the field lines. Electrostatic field lines are like hedgehogs: they begin and end at charges (or go to infinity). Magnetic field lines never resemble “hedgehogs”: they are always closed and embrace current currents.

To illustrate the application of the circulation theorem, let us find by another method the already known magnetic field of an infinite solenoid. Let's take a rectangular contour 1-2-3-4 (Fig. 6.31) and calculate the circulation of the vector IN along this contour

Rice. 6.31. Application of the circulation theorem B to the determination of the magnetic field of a solenoid

The second and fourth integrals are equal to zero due to the perpendicularity of the vectors and

We reproduced the result (6.20) without integrating the magnetic fields from individual turns.

The obtained result (6.35) can be used to find the magnetic field of a thin toroidal solenoid (Fig. 6.32).

Rice. 6.32. Toroidal coil: The lines of magnetic induction are closed inside the coil and form concentric circles. They are directed in such a way that, looking along them, we would see the current in the turns circulating clockwise. One of the induction lines of a certain radius r 1 ≤ r< r 2 изображена на рисунке