magnet It is a substance that generates a magnetic field and attracts magnetized materials to it.

History[عدل]

Al-Biruni devoted in his book Al-Jamahir fi Ma’rifat al-Jawhir a chapter on magnets, and pointed to the common characteristic between magnets and amber (electricity), which is their attraction to things, and indicated that magnets outperform amber in this capacity, and Al-Biruni indicated that most magnet materials are present in the countries of Anatolia and were manufactured Among them are the nails that are used in the manufacture of ships in those countries, while the Chinese used to build their ships by combining and tying planks of olive wood to each other with ropes of plant fibers, because there are mountains of magnet stone immersed in the waters of the China Sea that used to extract iron nails from the bodies of ships, so they disintegrated and sank in water.

magnetic materials[عدل]

An automagnet is a piece of matter that is magnetizable and produces a magnetic field by itself. Examples of these self-magnets are the magnets with which we beautify the refrigerator doors at home or with which we fix papers on iron boards at school. Magnetizable materials, which are also strongly attracted to a self-magnet, are called ferromagnetic or ferromagnetic. Among these materials, we find iron, cobalt, nickel, steel, and some alloys containing rare earth elements. While ferromagnetic (and ferromagnetic) materials are the materials that are strongly attracted to a self-magnet and are considered magnetic materials, other materials are weakly affected by a magnetic field in some way, and are characterized by another type of magnetic properties.

Self-magnets are made of a very “hard” ferromagnetic material by treating it in a strong magnetic field so that its magnetic crystal grains are directed in the direction of the external magnetic field. And it is difficult to lose its magnetism because of its hardness (not malleable). In order to demagnetize a magnet, a reverse magnetic field must be applied to it with a certain intensity that depends on what is called the magnetic resistance of the material. Hard magnetic materials have high magnetic resistance, while magnetically malleable materials have low magnetic resistance.

• The phenomenon of magnetism in materials is due to the electron that forms the atomic shells of the elements, which itself is considered a small magnet, as it has a magnetic moment resulting from the spin moment (see Bohr magneton).

magnet properties[عدل]

magnetic field[عدل]

The magnetic field is a vector field (the Earth’s magnetic field directs a magnetic needle). The magnetic field at any point has two characteristics:

1) Its direction, which is determined by the direction in which the compass needle takes it, 2) Its intensity, which is indicated by the extent to which the magnetic needle is obedient in taking its direction.

According to the International System of Units, the magnetic field unit is given in Tesla.

magnetic moment[عدل]

The magnetic moment is sometimes called the dipole moment and is usually denoted by the symbol – μ – which is a vector quantity and describes the general properties of magnets. For a magnetic bar, the direction of its magnetic moment passes from its south pole to its north pole. to the other.
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Its intensity depends on the strength of the poles and the distance of the poles from each other.

The unit of magnetic moment is measured in ampere. square meter, according to the International System of Units.

The magnet creates its own magnetic field around it, and it is affected by and interacts with an external magnetic field. The strength of the magnetic field it produces at a given point depends on the strength of its magnetic moment. In addition, when the magnet is placed in an external magnetic field resulting from another magnet or from another source, it is affected by a torque force that tries to direct it in the direction of the external magnetic field. The torque is proportional to the magnetic moment as well as to the strength of the external field.

The magnet may fall under the influence of a force that deviates it to a certain direction or another according to its location and direction in relation to the external field. If the external magnetic field is regular, the magnet does not suffer from tensile strength, but only from torque. (i.e. the compass needle takes the direction of the Earth’s magnetic field, and the needle (or compass) does not move from its place).

And if we form a wire in the form of a ring, the area of ​​which is A And we passed through the wire an electric current I that generates a magnetic field in the loop, and the loop becomes with a magnetic moment of magnitude I.A It is perpendicular to the ring and passes (essentially) through its center (the ring also creates a magnetic field around it.)

• By studying elementary particles such as the electron, proton and neutron, it turns out that each of them has a magnetic moment. The magnetic moment of each particle differs from the other (see Bohr magneton). The magnetic moment, for example, of an electron is due to its spin moment, as the electron always rotates around its axis.

magnetism[عدل]

The magnetism of a magnetized material is measured by the value of the magnetic moment per cubic meter in it and is usually denoted by the symbol
MIts unit is ampere/meter. Magnetism is a vector field, and a magnetic material can be magnetized in different places in a different direction of magnetism (such as magnetic grains in iron). It is considered a magnet with a magnetic moment of 0.1 A m² It has a volume of 1 cubic centimeter (1×10⁻⁶ Meter³) is a good magnet, and thus its magnetic strength is about 100,000 ampere / meter.

Iron is highly magnetic, as its magnetism can reach 1,000,000 ampere/meter. This explains why iron is mainly used to produce strong magnetic fields.

Iron follows cobalt and nickel in its magnetic strength, and these materials are called ferromagnetic materials, and we find these three adjacent elements in the periodic table of the elements, where the electron shell of their atoms is similar in them (their atomic numbers are 26, 27, and 28, respectively).

types of magnetism[عدل]

Magnets are made of iron, cobalt, nickel, or some alloys of these materials, and they are called ferromagnetic materials, and their properties are strongly attracted to a self-magnet. As for the other materials, they show the phenomenon of magnetism in different ways, and their magnetism is weak in general.

The characteristic of magnetism (which depends on the electronic configuration in atoms) is divided into the following categories:

• Ferromagnetic
• frimagnetism
• Paramagnetism
• opposite magnetic
• Anti-ferromagnetism

magnetic granules[عدل]

Magnetic materials, including ferrimagnetic materials, are characterized by the fact that their atoms themselves are magnetic, due to the spin moment of the electron, which is accompanied by a magnetic moment, that is, the electron is considered a small magnet. Among the properties of ferromagnetic materials in particular, such as iron, cobalt, and nickel, the electrons that occupy the 3d orbit in their atoms take the same direction, and thus the iron atom, the cobalt atom, and the nickel atom become distinguished with a large magnetic moment. Neighboring atoms in the material are affected by each other’s magnetic field, and take the same direction, forming a magnetic granule. Magnetic ‘granules’ are formed – including many millions of atoms in the material (the grain section is about 10 micrometers, see picture) – but the orientation of the magnetism of the grains is randomly distributed so that their magnetic result is zero. When placed in a magnetic field, these granules tend to take the direction of the external magnetic field, thus increasing the magnetism of the sample. And by increasing the intensity of the external magnetic field, the number of particles that orient themselves in the direction of the external field increases, and the magnetism of the sample increases. If the intensity of the magnetic field applied to it from the outside increases greatly, we find that the magnetism of the material reaches a limit magnetic saturation Where all the magnets of the particles have taken a direction parallel to the external magnetic field. The upper limit of magnetic saturation is a property of some materials and varies from one material to another (and also varies for iron, cobalt and nickel).

When the ferromagnetic material reaches a limit saturation It continues to increase its magnetism weakly through paramagnetism, but this is about 1000 times weaker than ferromagnetism.

Electromagnet[عدل]

The simplest type of electromagnet consists of a wire coil in which an electric current passes and a magnetic field is concentrated inside and around it. The magnetic field lines are similar to the magnetic field lines of a magnetic bar. The direction of magnetism in the coil is determined according to the right-hand rule. The strength of the generated magnetic field is directly proportional to the number of coil turns, the area of ​​the coil loop, and the intensity of the electric current passing through the coil.

If a cylinder of non-magnetic material (such as a cylinder of paper or cardboard) is placed in the coil, a weak magnetic field will be generated in it. But if a ferrous magnetic material such as a bar of iron or several iron nails is placed inside the spiral, then the strength of the generated magnetic field increases and can reach a thousand times the strength of the field of the empty coil. Electromagnets are used in particle accelerators, electric generators, magnetic resonance imaging (MRI) scanners, and electron microscopy.

magnet applications[عدل]

The magnet is considered one of the most important materials available to us in our current era, and it is one of the most important inventions that appeared in the field of physics. Since the beginning of the discovery of the magnet stone in the city of Magnesia in Turkey, human thought has been trying to find uses and uses for this stone that attracts minerals. With the beginning of development, it made and invented the industrial magnet as we see it today. It has been used amazingly and surprisingly, especially in the field of transportation (rapid electric trains and electric buses), information storage in computers, image and sound recording devices such as hard disks, cassettes, and others in devices used by physicists in their experiments such as particle accelerators, such as the Large Hadron Collider and Fermilab.

Magnet uses[عدل]

1. Generating electric current, and this use is considered the most important use of magnets in our current era, because it produces the most important source of energy for the world, and the method of magnet generation of electricity was discovered by the scientist Faraday, where he rotated a two-pole magnet around a file, so the magnet generates a magnetic field, which turns into an electric current that runs in the wire and this The process is the opposite of the process of producing kinetic energy by passing an electric current around a magnet to generate a magnetic field opposite the magnet to rotate.

2. Magnetic trains, and this use is considered one of the wonders of physics that many inventors and physicists dreamed of, which is to make a huge body like a train float above the air, but the magnet is not the only factor in this process, but rather superconducting materials are used for the electric current that do not have any resistance to the electric current and to be resistant These materials for electric current are zero, their temperature must be reduced to very low rates, and with all the attempts of the inventors in our time, the largest temperature that is easy to provide for the superconducting materials to perform their function is approximately 70 K, and in order to reach this degree, the superconducting materials must be immersed With liquid nitrogen, which is widely available and has a relatively reasonable cost according to the cost of other materials such as liquid helium, which is very expensive. When the temperature of these materials decreases, the magnetic field coming from one pole of the magnet to the pole of the other is reversed, so that the magnet is suspended and floating in the air at the same time. Then the train floats in the air and moves at a very high speed because there is no friction between the train and the track

3. Medical uses Magnets are widely used in this field, and one of the most important uses in this field is the MRI device, which is a revolution in the field of medicine and is one of the most important innovations that help medical science in detecting tumors, diseases and other harmful bodies in the body.

4. In home recording devices, such as computers, floppy disks, hard disks, cassettes, and electric amplifiers.

See also[عدل]

• electromagnet
• geomagnetism
• magnetism
• Paramagnetism
• Ferromagnetic
• rock magnetism
• opposite magnetic
• refrigerator magnets
• gravitational magnetism
• permeability (electromagnetic)
• magnetic field strength

Related topics[عدل]

• magnetic susceptibility
• magnetic saturation
• geomagnetism
• Ferromagnetic
• Paramagnetism
• opposite magnetic
• frimagnetism
• ferrite (magnetic)
• Korean law
• Oersted
• Gilbert (unit)

the reviewer[عدل]

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