Disadvantages Of Magnetism

The first scientific study of magnetism was made by the Englishman William Gilbert (1540-1603), who published his classic book ON THE MAGNET in 1600 [17]. His experiments with lodestone and iron magnets formed a clear picture of the Earth’s magnetic field. In the eighteenth century, compound steel magnets were made, which was composed of many magnetized steel strips fastened together, which could lift 28 times their own weight of iron. Initially, there was only one way of making magnets at that time: the iron or steel had to be rubbed with a lodestone, or with another magnet which in turn had been rubbed with a loadstone. There was no other way until the first electromagnet was made in 1825, which followed the great discovery made in 1820 by

The three unit systems are the Gaussian or cgs system and two MKS unit systems, namely the Sommerfeld convention and the Kennelly convention. Each of these unit systems has different advantages and disadvantages. The cgs system is based on the approach using magnetostatics and the concept of magnetic pole, while SI system is based on electrodynamics approach to magnetism based on electric currents. The SI system was adopted at the 11th General Congress on Weights and Measures (1960). Table 1 summarizes the basic units and equations of these three

In absence of the external magnetic field, the atomic magnetic moments are randomly oriented. This makes the net magnetic moment and hence the magnetization of material becomes zero. But when an external magnetic field is applied through the material, the individual atomic magnetic moments tend to align themselves in the direction of magnetic field which results in a non-zero magnetization.

There are several theories proposed for Paramagnetism, which are valid for specific types of materials. According to the Langevin model, which is true for materials with non-interacting localized electrons, states that each atom has a net magnetic moment which is randomly oriented as a result of thermal agitation. The application of an external magnetic field creates a slight alignment of these magnetic moments and hence a low magnetization in the same direction as the applied field. As the temperature increases, the thermal agitation will increase and it will be much harder to align the atomic magnetic moments and hence the susceptibility will decrease. This behavior is known as Curie law and given