المغنطيسية - الطاقة الكهربائية .. الفيزياء

Magnetism - Electrical Energy .. Physics

Magnetism

The presence of attractive or repulsive forces is not limited to electrically charged objects only, but also extends to magnetic materials such as magnetite, which is found in nature in the form of iron oxide ore.

The magnetic properties appear, at first glance, to be concentrated in two small areas at the ends of the magnet called the poles of the magnet, and when a magnetic rod is suspended and left alone, one of its ends points directly north, and is therefore called the north pole of the magnet, and the other end is called the south pole, and it is known that the north pole attracts the south pole and that two poles of the same type repel each other.

Unlike electrical charges, it is impossible to isolate the pole of a magnet from the other pole because they are always coupled to each other, and therefore the magnet is called a dipole.

The medium surrounding a magnet, in which magnetic forces are strongest, is the magnetic field of this force. The electric field determines the place where the electric forces are effective. When two electric fields intertwine, a certain interaction occurs between them. As for the magnetic field, it has lines of force that indicate its direction and are always issued from its north pole and end at its south pole.

(The shape of the lines of force around two pieces of magnet.

If we symbolize K1 and K2 for the masses of the magnet located at two poles at a distance F from each other, the force of attraction or repulsion between them becomes 1H K1 and K2 / F2, where 1H represents the permeability of the medium surrounding the poles)

Some metals, such as iron, nickel and some alloys, are more magnetic than other materials, and they acquire this characteristic, especially ferromagnetism. Ferromagnets exist in nature in their usual magnetic state. However, they are made in different ways, all of which are summarized by placing them in an electromagnetic field, then removing this field, so some types of ferromagnets retain their magnetic properties to a high degree (strong magnets), while the remaining types lose this property very quickly (weak magnets). Ferromagnets lose all their magnetic properties above a certain temperature that varies according to the materials and is called the Curie temperature, and in this case they become a ferromagnet with very weak magnetic properties. (When a magnetic bar is placed in a certain magnetic field, its poles are subject to the influence of two forces of equal value but opposite)

Magnetic sectors

The magnet breaks and divides into small parts, each of which forms an independent magnet from the other. Since most types of iron magnets must be magnetized because their magnetic properties are gradually removed by heat, for example, we can say that each iron magnet consists of a large number of fine magnetic parts that in turn consist of large groups of atoms linked to each other by mutual forces resulting from the movement of electrons in them. This movement is not limited to the rotation of the electron around itself, but also includes its rotation around its axis, and this is known as this connection between the groups makes each of them an independent magnet by twisting, very small, called the magnetic sector, and it contains approximately 1510 atoms, meaning that 6000 sectors of it are necessary to fill a volume the size of a pinhead. It is noted that before the iron magnet crystal becomes magnetized, the magnetic fields in its various sectors take all possible directions so that its magnetic property is almost non-existent. However, when a magnetic field is applied to it, its fine parts begin to line up in the direction of the field itself so that the material then becomes a magnetized material.

The Earth's Magnetic Field

The magnet continues to move if left to itself, and does not stop except when its north pole points north. The magnet has been used throughout the past centuries inside the compass to determine directions in navigation. Because there is a force of attraction between two different magnetic poles, there must be a magnetic field for the Earth itself, which acts as if there is a huge magnetic pole inside it parallel to the north-south direction. The source of the Earth's magnetic field is still unknown to this day, and it cannot be the result of the magnetism of the Earth's iron core, because the temperature of the Earth's interior, which is composed of iron and nickel, is very far from the Curie temperature. Since magnetism is generated by the movement of electric current, it is believed that there are weak electric currents inside the Earth resulting from the movement of fluid materials in its core.