Lesson № 2 Theme: Molecular theory of magnetism

1. to acquire the special text with the aim learning the necessary information.

2. to learn lexical minimum and to use it in practice.

3. to communicate in English with partner on this subject

1. 
   The modern theory of magnetism, which is now quite firmly established as being correct, is that a piece of iron consists of tiny elementary magnets. These tiny ultramicroscopic magnets consist of individual atoms.
   
2. 
   Before a piece of iron or steel has been magnetized, these elementary magnets may be thought of as being oriented more or less at random throughout the metal.
   
3. 
   During the time a piece of iron is being magnetized, these elementary magnets are turned around and lined up parallel to each other and to the magnetizing field. Lined up in this way, the small N and S poles are adjacent to each other and cancel each other’s effect on external objects. At one end there are many free N poles, and at the opposite end an equal number of free S poles.
   
4. 
   When a magnet is broken at any point, free S poles are exposed at one side of the break and free N poles at the other. It is therefore clear why poles always exist in pairs and that, no matter how many times a magnet is broken, each peace will contain an N at one end and an S pole at the other.
   
5. 
   When soft iron is magnetized by induction and the permanent magnet is taken away, the elementary magnets return to their original random orientations, but, when hardened steel becomes magnetized, they remain lined up after the magnetizing field is taken away