A magnet is a material or object that produces a magnetic field. A magnet exerts a force on similar materials that either pulls the objects toward one another or repels one another.
Materials are classified into different types depending on their effect with magnetism. They are as follows:
- Paramagnetic materials are not strongly attracted to a magnet. For example, aluminium, tin, magnesium etc. Their relative permeability is small but positive. Such materials are magnetized only when placed in a very strong magnetic field and act in the direction of the magnetic field.
Paramagnetic materials have individual atomic dipoles oriented in a random fashion as shown in the figure below.
The resultant magnetic force in such materials is zero. When a strong external magnetic field is applied, the permanent magnetic dipoles orient them self-parallel to the applied magnetic field and give rise to a positive magnetization. Since, the orientation of the dipoles parallel to the applied magnetic field is not complete, the magnetization is very small.
- Diamagnetic materials are repelled by a magnet such as zinc, mercury, lead, sulphur, copper, silver, wood, etc. Their permeability is slightly less than one. They are slightly magnetized when placed in a very strong magnetic field and act in the direction opposite to that of applied magnetic field. In diamagnetic materials, the two relatively weak magnetic fields caused due to the orbital revolution and axial rotation of electrons around nucleus are in opposite directions and cancel each other. Permanent magnetic dipoles are absent in them, Diamagnetic materials have very little to no applications in electrical engineering.
- Ferromagnetic materials are material that are strongly attracted by a magnetic field or magnet. For example, iron, steel, nickel, cobalt etc are ferromagnetic materials. The permeability of these materials is extremely high. The opposite magnetic effects of electron orbital motion and electron spin do not eliminate each other in an atom of such a material. There is a relatively large contribution from each atom which aids in the establishment of an internal magnetic field, so that when the material is placed in a magnetic field, its value is increased many times the value that was present in the free space before the material was placed there.
- Ferrites are a special type of ferromagnetic material that occupy an intermediate position between ferromagnetic and non -0ferromagnetic materials. The magnetization produced in ferrites is large enough to be of commercial value, but their magnetic saturation is not as high as those of ferromagnetic materials. As in the case of ferromagnetic, ferrites may be soft or hard ferrites.
Types of Magnets
Based on properties magnets can be classified into different types. They are mentioned below.
- A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. Permanent magnets are known to retain their magnetic property unless they are necessarily demagnetized using any of the following methods:
- The magnetic properties between the atoms of the magnet weaken when exposed to extreme temperatures.
- Hammering on the magnets will loosen the magnetic strength.
- Improperly stroking one magnet with another also reduces the magnetic attraction properties of permanent magnets.
- Temporary magnets are defined as magnets such that when the material is placed in a magnetic field it acts as a permanent magnet. Temporary magnets lose their magnetism after the magnetic field is removed. Unlike permanent magnets, temporary magnets do not retain their magnetic property. Therefore, they are called temporary magnets. Some irons, iron alloys, iron nails and paper clips act as a temporary magnet in the presence of a magnetic field.
- Electromagnets are the magnets created by winding a wire in several loops around a metal core composed of iron. When this arrangement known as solenoid is placed by the electric field and an electric current is passed through it, the wires energised coil generates the magnetic field which eventually acts as a magnet. The strength of magnetism can be controlled by adjusting or altering the electric current's strength and direction. Besides, the field inside the prepared coil is the highest, and the strength of the field is directly proportional to the number of wire loops and the carried current. When the electric current is stopped, the magnetic field disappears, and so the metal's magnetism property. The material used in the centre of the electromagnet arrangement may also influence the overall electromagnet's power. As a result, electromagnets also are not permanently magnetic.
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