Theory of Magnetism

                             Theory of Magnetism

The molecule of a magnetic substance (Where magnetized or not) is a complete magnet in itself having a north pole and a south pole of equal strength.

                    i.            In an un-magnetized substance, the molecular magnets are randomly oriented. The north pole of one molecular magnet cancels the effect of the south pole of the other so that the substance does not show any net magnetism.

 

 

 

 

           In absence of magnetic field                  In Presence of magnetic field

                  ii.            When a magnetizing force is applied to the substance, the molecular magnets are turned and tend to align in the same direction with the N-pole of one molecular magnet facing the S-pole of the other. The result is that the magnetic field of the molecular magnets aid and two definite N and S-pole are developed near the ends of the specimen; the strength of the two poles being equal. Hence the substance gets magnetized.

                iii.            The extent of the magnetization of the substance depends upon the extent of alignment of molecular magnets. When all the molecular magnets are fully aligned, the substance is said to be saturated with magnetism.

               iv.            When a magnetized substance (or a magnet) is heated, the molecular magnets acquire kinetic energy and some of them lost their arrangement. For this reason, a magnet loses some magnetism on heating.