One of the basic concepts used in physics is a magnetic field. It acts on moving electric charges. Unnoticed and not felt by a person, however, its presence can be detected using a magnet or iron. It is also easy enough to understand which magnetic field is called homogeneous and inhomogeneous.
Definition and methods for detecting a magnetic field
When we come across the concept of a magnetic field, the question arises as to what kind of magnetic field it is, whether it is homogeneous or inhomogeneous. Before answering such a question, initial definitions of terms should be given.
The magnetic field is supposed to be considered a special type of matter existing near moving electric charges, especially near conductors with current. You can detect using a magnetic needle or iron filings.
Uniform field
It occurs inside the strip magnet and in the solenoid when its length is much larger than the diameter. In this case, according to the drill rule, the magnetic field contours will be directed counterclockwise.
The magnetic lines are parallel and straight, the void between them is always the same, the force of influence on the magnetic needle does not differ at all points in magnitude and direction.
Heterogeneous field
In the case of an inhomogeneous field, the magnetic lines will bend, the void between them varies in magnitude, the force acting on the magnetic arrow differs at different points in the field in magnitude and direction. Also, the force acting on the arrow placed in the field of the strip magnet acts at various points with forces different in modulus and direction. This is called a non-uniform field. The lines of such a field are curved, the frequency varies from point to point.
It is possible to detect this kind of field near a direct current conductor, a strip magnet and a solenoid.
What are magnetic lines
First of all, when a problem arises, it is necessary to determine which magnetic field, homogeneous or inhomogeneous, is formed, you should learn about magnetic lines, the shape of which makes it possible to understand the field characteristics.
To depict a magnetic field, magnetic lines began to be used. They are imaginary stripes located along the magnetic needle and placed in a magnetic field. It is possible to draw a magnetic line through any point in the field, it will have a direction and will always close.
Direction
They leave the north pole of the magnet and head to the south. Inside the magnet itself, everything is exactly the opposite. The lines themselves do not have a beginning or an end, are closed or pass from infinity to infinity.
Outside the magnet, the lines are located as densely as possible near the poles. From this it becomes clear that the effect of the field near the poles is most pronounced, and as it moves away from the bottom it weakens. Given that the magnetic strips are curved, the direction of the force that acts on the magnetic arrow also changes.
How to portray
To understand how homogeneous magnetic fields differ from inhomogeneous ones, it is necessary to learn how to draw them using magnetic lines.
Consider the above-mentioned example of the appearance of a uniform magnetic field in the so-called solenoid, which is a cylindrical wire coil through which a current is introduced. Inside it, the magnetic field can be considered homogeneous, provided that the length is much larger than the diameter (outside the coil, the field will be inhomogeneous, the magnetic lines will be located in the same way as for a strip magnet).
A uniform field is also located in the center of the permanent strip magnet. In any limited region in space, it is possible to reproduce a uniform magnetic field in which the forces acting on the magnetized arrow will be identical in modulus and direction.
To depict the magnetic field, use the following example. If the lines are perpendicular to the drawing plane and are directed away from the beholder, then they are drawn with crosses, if on the beholder, with dots. As with the current, each cross is like the visible tail unit flying from the looking arrow, and the point is sharper than the arrow that flies towards us.
Also, the requirement “Imagine a uniform and inhomogeneous magnetic field” is easily feasible. Simply draw these magnetic lines, taking into account the characteristics of the field (uniformity and heterogeneity).
However, the existence of inhomogeneous fields greatly complicates the task. In this embodiment, obtaining any physical result using the general equation is unlikely.
Differences
The answer to the question of how homogeneous magnetic fields differ from inhomogeneous ones is quite easy to give. This primarily depends on the magnetic lines. In the case of a homogeneous field, the distance between them will be the same, and they will be evenly spaced, acting with the same force on the instruments at any point. For heterogeneous fields, the opposite is true. The lines are unevenly located, in different places they act with unequal force on the devices.
In practice, an inhomogeneous field is often encountered, which should also be remembered, since homogeneous fields can only be found inside an object, such as a magnet or a solenoid. External observations will record heterogeneity.
Field detection
Having understood what homogeneous and inhomogeneous magnetic fields are, and having analyzed their definitions, you should find out how to detect them.
The easiest for this is the experience conducted by Oersted. It consists in the use of a magnetic needle, which helps to determine the existence of an electric current. As soon as the current moves through the conductor, a nearby arrow will move, due to the fact that there are uniform and inhomogeneous magnetic fields.
Interaction of conductors with current
Each conductor with current has its own magnetic field, acting with a certain force on the nearest one. Depending on the direction of the current, the conductors will be attracted or repelled from each other. Fields arising from various sources will add up and form a single resulting field.
How are they created and why
Examples of a uniform and inhomogeneous magnetic field used in cathode-ray devices are created by coils that pass current. To obtain the necessary shape of the magnetic field, shelf tips and magnetic screens made of materials having strong magnetic permeability are used.
The influence of inhomogeneous magnetic fields can change the course of irreversible phenomena of a physicochemical nature, mainly a heterogeneous process. The appearance of turbulent diffusion leads to an increase by several orders of magnitude of the velocity of gas movement from any liquid to the surface in the form of micro bubbles. The effect of local dehydration of ions and particles is due to the intensification of the microcrystallization process. In flowing media, high-energy reactions are capable of creating free radicals, atomic oxygen, peroxides, and nitrogen compounds. Coagulation occurs, and products caused by erosion destruction appear in the liquid.
During hydrodynamic cavitation, the large size of the emerging bubbles and caverns complicates their liquid entrainment from the territory of reduced pressure to the zone of higher pressure, where the bubbles collapse. During the collapse of a small bubble, there is a low air content and a strong chemical reaction similar to a plasma discharge occurs. The presence of inhomogeneous magnetic fields leads to instability of caverns, their decay, and the appearance of small-scale vortices and bubbles. Considering that the pressure in the center of such a vortex is reduced, it converts gas bubbles of a small size.
When measuring induction in an inhomogeneous magnetic field, it should be remembered that the Hall voltage is proportional to the average value of the field induction within the territory limited by the transducer surface.
In order to focus paraxial beams, inhomogeneous magnetic fields formed by short coils, which are multilayer solenoids, the length of which is comparable with their diameter, are also used. The electron falling into such a field is affected by forces that change its direction. Under the influence of such a force, an electron approaches the axis of the lens, while the plane in which its path is curved. The electron moves along a spiral segment that intersects the axis of the lens at a given point.
The spatial factor of the increase is caused by the spatial distribution of inhomogeneous fields in the territory of the heterogeneous system, washed down by the liquid. To obtain the inversion of the level population by the separation method, inhomogeneous fields created by a multiband magnet are used. The shape of the poles is similar to the rods in a quadrupole capacitor of a molecular generator on ammonia.
Ways to use
The magnetic-ordinal method of defectoscopy is based on the traction of magnetic particles by the forces of inhomogeneous fields appearing over defects. From the accumulation of such a powder, the presence of the defect, its size and position on the tested part are determined.
A considerable disadvantage of the molecular beam method using strong inhomogeneous magnetic fields is the small splitting effect. There is a simple and seemingly implausible method to increase this effect. It consists in the use of a light external magnetic field. The latter will make it possible to increase the use of nuclear precession magnetometers in the direction of inhomogeneous magnetic fields.
The advantage of this method is its high resolution, which makes it possible to fix inhomogeneous magnetic fields commensurate with the size of the particles of the magnetic layer of the tape, as well as the possibility of finding damage on complex surfaces and in tight openings.
The disadvantages are the need for secondary processing of information, only particles of magnetic fields along the tape are fixed, the complexity of demagnetization and conservation of the tape, and the influence of external magnetic fields must be prevented.
A uniform and inhomogeneous magnetic field is quite common, despite the fact that it is invisible to a simple layman. Examples of a uniform and non-uniform magnetic field can be found in strip magnets and solenoids. At the same time, you can notice them using the simplest magnetic needle or iron filings.