In order as an example to interpret the concept of electromagnetic induction, that she is to the base of the behavior of all blots them of it static electrical workers, like the transformers and of those dynamics, like the electric motors, the magnetic and electromagnetic phenomena must be known fundamental. We begin therefore with the presentation and the definition of some natural elements or adequately deals to you, that they constitute sources of the magnetic fields.
With the words "magnet" and "magnetizes", is designated normally of the bar of steel, that they can straight or be withdrawn and that they have the property to attract small cast iron, steel, iron objects or fragments and, in smaller measure, also of cobalt, nickel, chromium and of other metals. All these elements, when they are subordinates to the influence of a magnet, magnetize to they time, that is same magnets or magnets become they. Some of these, then, in particular way the moderated steel, remain magnetize to you stability or, at least, for a time along and in such state they constitute "permanent magnets much"; others instead, like the sweet iron, remain only magnetize to you until remain under the influence of an other magnet and in such state they represent "temporary magnets".
Modern physics has demonstrated that the magnetic actions, that is the magnetic phenomena, are manifested, is also in measure ridottissima, sometimes not even noticeable from the more sensitive instruments, also in the various bodies from those cited, as an example in those gaseous and liquids. There are however of the substances that manifest opposite phenomena of complementary magnetism to that they are manifested in the bodies before mentions to you. Between which we remember bismuth, that it has the property of being rejected from magnets rather than attracted.
The bodies of the type of bismuth are in much limited number and come call to you DIAMAGNETIC, while all the others are call to you PARAMAGNETIC.
In practical those in which are defined with the name of magnetic bodies the magnetic actions are particularly intense and between these the ferromagnetic materials assume essential importance.