Basic principles of magnets
- You will find all the basic concepts you need to know in the following text where we explain the basic principles of magnets.
Magnets; definition and properties
A permanent magnet is a body with vicinity in which there is a permanent magnetic field. Permanent magnets consist of iron, nickel, cobalt and ferromagnetic materials or their alloys. Other magnetisable materials are the rare earth metals neodymium and samarium. The magnetic field of the permanent magnet causes nearby objects, which are also made of magnetisable material, to be attracted. When permanent magnets are used as holding magnets, they also attach to steel bodies of automobiles or refrigerator doors. On the other hand, their use as magnets on almost all other metals is not possible, even with aluminium or copper, as these substances do not have magnetic properties.
How a magnet works after magnetizing
It is only through the magnetization process a permanent magnet obtains its magnetic properties. In the not yet magnetized state, all the elemental magnets of the body are found, which must first become a disordered magnet.
As a result, the magnetic effects of elementary magnets cancel each other out. In sintered magnets, the powdered magnetic material is exposed to an external magnetic field. This external magnetic field causes a uniform orientation of the elementary magnets, which also adds up to their magnetic properties. In this state, the magnet is compressed at high pressure at a certain temperature. This process is called sintering. After the magnet activates the process, the permanent magnet retains its magnetic properties, even if the external magnetic field is removed again. However, it is important for the subsequent use of permanent magnets that they are treated with care. This also means that they are not exposed to sudden shocks. This could lead to a reduction of the magnetic properties or even to their complete loss. The allowed operating temperature must not be exceeded, as this also affects the magnetic properties of permanent magnets.
Factors that influence magnetic properties and attraction
In addition to determining the magnetic characteristics of a permanent magnet after the magnetization process, there is another method for determining the magnetic strength of magnets. The permanent magnet is clamped to its magnetization in a piece of metal. Now, the permanent magnet is removed from the metal plate by means of a tensile force measuring device. This type of tensile force measurement is known as Tensile Force Case 1 (Tensile Force Case 1). The size of the determined tensile force is a measure of the magnetic field strength of the permanent magnet.
Another method of measurement is the determination of the peeling force according to the tensile force Case 2 (tensile force Case 2). In this measurement method, the permanent magnet to be tested is also clamped to a piece of metal. At the bottom, opposite the metal piece, a second piece of metal is clamped to the permanent magnet. This second piece of metal is now also removed from the permanent magnet by means of a new tensile measuring device. The measured force is lower than with traction box 1.
In a third measurement method, the shear force is also determined according to the tensile force Case 3 (tensile force Case 3). Again, the permanent magnet to be tested is stapled to a piece of metal. A permanent magnet identical to the magnet to be tested is attached to the bottom of the first permanent magnet. Of course, this happens so that two different poles always touch each other, because only the different magnetic poles attract each other. Now, the second magnet is also deduced from the first magnet by means of a traction measuring device. Here again, a measured value describing the strength of the magnetic field is obtained. The detachment force of the magnets that are bonded directly is the same as after the tensile force in Case 1.
Permanent magnets can magnetize other objects such as screwdrivers. The magnet is guided with one of its magnetic poles to the end of the screwdriver shaft where the metal piece begins. Now, move the magnet along the metal piece to the end of the head. Then, move the magnet vertically away from the metal piece of the screwdriver and lead it some distance from the screwdriver back to the shaft end. Repeat the same process several times. The screwdriver thus receives magnetic properties.
If several magnets influence each other by a small distance, the analytical processing of the resulting magnetic fields is very difficult. In any case, it depends on the practical results of the test.
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