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A magnet is an object that creates a magnetic field in the space around it. It can take the form of a permanent magnet or an electromagnet. Permanent magnets do not need any external energy to create a magnetic field. They occur naturally in some minerals, but can also be crafted. Electromagnets need electricity to create a magnetic field.


 Properties of magnets
Magnets are attracted or repelled by other materials. A material that is strongly attracted to a magnet has high permeability. Iron and steel are two examples of materials with very high permeability and are very strongly attracted to magnets. Water has such a low permeability that it is easily repelled by a magnetic field.

The SI-is unit of magnetic induction, which is incorrectly thought of as the "intensity" of a magnetic field, is the tesla (symbol T). A homogeneous magnetic field having a magnetic induction of 1 T exerts a force of 1 newton on each meter of a straight conductor carrying an electric current of 1 ampere. The SI unit of magnetic field strength is the ampere per meter (A/m). The SI unit of magnetic flux is the Weber (symbol Wb). The magnetic flux is the product of the magnetic induction and the area through which the field passes; 1 Wb = 1 T·m2. It is a very high value of magnetic flux.




The word magnet comes from the Greek μαγνήτης λίθος (magnētēs lithos), meaning "magnesium stone". Magnesia was an area in Ancient Greece, today's Manisa in Turkey, where deposits of magnetite were discovered already in antiquity. Ancient Chinese navigators were among the first recorded users of magnetic compasses.

The legend of the magnetic mountain played an important role in the mythology of Arab sailors. In the fifteenth century, the Arabs were so afraid of the magnetic mountain that they did not use any iron objects (not even nails) in their vessels.


Physical origin of magnetism
Permanent magnets
Matter is made up of particles such as protons, neutrons, and electrons, all of which have a basic property: quantum mechanical spin. Spin gives each of these particles a certain magnetic field. Therefore, all matter would be expected to be magnetic, and even antimatter would have magnetic properties. However, this is not the case.

In each atom and molecule, the spin of these particles is strictly ordered according to the Pauli exclusion principle. But this principle of spin arrangement does not apply to the large distance between atoms and molecules. Without this distant arrangement, there is no net magnetic field because the magnetic moment of each of the particles is disturbed by the moment of the other particles.

Permanent magnets are special in that they have a long-range arrangement. The highest degree of order exists in magnetic domains. This can be compared to microscopic neighborhoods in which there is a strong interaction between particles and a high level of order results. The higher the order in the domain, the stronger the resulting field.

Distant ordering (and the resulting strong magnetic field) is the main feature of ferromagnetic materials.

Electrical creation of magnetism
Electrons play a major role in creating a magnetic field. Inside an atom, electrons can exist either singly or in pairs in any orbit. If they are paired, the individual electrons from this pair have the opposite spin – one upper, the other lower. The fact that the spins are opposite means that they cancel each other out. If all the electrons are paired, no magnetic field is created.

There are unpaired electrons in some atoms. All magnets have unpaired electrons, but not all atoms with unpaired magnets are ferromagnetic. For a material to be ferromagnetic, it must contain unpaired electrons, but these must interact over a long distance so that they are all oriented in the same direction. The specific position of the electrons in the atom (and also the distance between the atoms) is what creates the long-range arrangement. Electrons have lower energy if they are equally oriented.

An electromagnet in its simplest form is a wire wound into one or more loops. Such a loop is called a solenoid. When an electric current passes through the loop, a magnetic field is created around it. The orientation of this field can be determined by the right-hand rule. The strength of the field is affected by several factors. The number of loops determines the range of action, the amount of current determines the amount of activity, and the material in the core determines the electrical resistance. The more loops and the higher the current, the stronger the magnetic field will be.

If the loop is hollow in its center, it will generate only a very weak field. Various ferromagnetic or paramagnetic things can be inserted into the center of the coil, which will strengthen their magnetic field, such as an iron nail. Soft iron is commonly used for this purpose. Adding such things can amplify the field hundreds to thousands of times.

Over long distances, magnetic fields obey the inverse square law. This means that the field strength is inversely proportional to the square of the distance from the magnet.

If a magnet is in contact with a flat sheet of metal, the force required to separate them must be greater the closer the contact between the two surfaces. The smoother the surfaces, the greater the number of contact points between them and the less resistance there is between the magnetic circuit and the magnetic field.

Electromagnets are used in many applications, from particle accelerators to scrap yard cranes to magnetic resonance imaging machines. There are also special processes that require more than a simple dipole magnet, such as the quadrupole magnet used for focusing particle beams.

If enough current flows through the loop of the electromagnet, the magnetic force between adjacent coil loops can cause the electromagnet to be crushed by its own magnetic force.

and where they all lie, there is no single point where they all are. Every single person has a forehead on one side and a back on the other. When the line is split in half, each half will still have a head and a tail. Even if we divide the line into individual people, each of them will have their own front and back. In this way, you can proceed to infinity.

It's the same with magnets. There is no place on the magnet where all the south or north poles are located. When a magnet is split in two, both will have a north and a south pole. These two smaller magnets can be divided further and each part will have both poles. In most cases, what happens is that when we divide the material into smaller and smaller parts, we will eventually reach a point where the individual particles will be so small that they cannot maintain a magnetic field. However, they do not become separated poles, they just lose the ability to maintain a magnetic field. But some materials can be broken down to the molecular level and they still retain a field with a south and a north pole. There are theories about separate south and north poles - magnetic monopoles, but no such monopole has yet been found anywhere.

Determination of the North Pole and the Earth's magnetic field
Standard naming of magnet poles is important. Already in history, the terms north and south indicated an awareness of the relationship between magnets and the earth's magnetic field. A freely supported magnet will always rotate from north to south over time because it is attracted to the north and south poles of the earth. The end of the magnet that points to the Earth's geographic north pole is called the north pole of the magnet, the part that points to the south is called the south pole of the magnet.

The current geographic north pole is actually magnetic south. To complicate matters further, magnetized rocks on the ocean floor show that the Earth's magnetic field has reversed in the past, so this pole naming is likely to reverse again in the future.

Fortunately, by using an electromagnet and the right-hand rule, the orientation of a magnet's magnetic field can be determined even without knowledge of the Earth's geomagnetic field.

To avoid problems between geographic and magnetic poles, magnets are often labeled positive and negative poles. The one that turns north is positive.

Vytvořil Shoptet | Design Shoptetak.cz.