Weber and Ewing’s Molecular Theory

Weber and Ewing’s Molecular Theory

This theory was 1st advanced by Weber in 1852 and was, later on, more developed by Ewing in 1890. the fundamental assumption of this theory is that molecules of all substances ar inherently magnets in themselves, every having a N and S pole. 

In AN unmagnetised state, it's supposed that these tiny molecular  magnets exist all forms of haphazard manner forming additional or less closed loops (Fig. 6.5). per the laws of attraction and repulsion, these closed magnetic circuits ar glad internally, thus there's no resultant external magnetism exhibited by the iron bar. 

But once such AN iron bar is placed in a very force field or underneath the influence of a magnetising force, then these molecular magnets begin turning spherical their axes and make up one's mind themselves additional or less on straight lines parallel to the direction of the magnetising force.

This linear arrangement of the molecular magnets leads to N polarity at one finish of the bar and S polarity at the opposite (Fig. 6.6). because the tiny magnets flip additional nearly within the direction of the magnetising force, it needs additional and additional of this force to provide a given turning moment, therefore accounting for the magnetic saturation. 

On this theory, the physical phenomenon loss is meant to ensue to molecular friction of those turning magnets. owing to the restricted information of molecular structure out there at the time of Weber, it had been out of the question to clarify first, on why the molecules themselves ar magnets and second, why it's not possible to magnetise sure substances like wood etc. 

The first objection was explained by Ampere United Nations agency maintained that orbital movement of the electrons around the atom of a molecule implanted a flow of current that, thanks to its associated magnetic result, created the molecule a magnet.

Later on, it became troublesome to clarify the development of magnetism (shown by materials like water, quartz, silver and copper etc.) erratic behaviour of magnetic force (intensely magnetisable) substances like iron, steel, cobalt, nickel and a few of their alloys etc. and therefore the magnet (weakly magnetisable) substances like element and metallic element etc.

 Moreover, it had been asked : if molecules of all substances ar magnets, then why doesn't wood or air etc. become magnetic  ? All this has been explained satisfactorily by the atom-domain theory that has outdated the molecular theory. it's on the far side the scope of this book to travel into the main points of this theory.

 The interested reader is suggested to visit some customary book on magnetism.  However, it should simply be mentioned that this theory takes under consideration not solely the planetary motion of AN lepton however its rotation concerning its own axis likewise.  This latter rotation is termed ‘electron spin’.  The rotating mechanism behaviour of AN lepton provides rise to a moment of a magnet which can be either positive or negative.

 A substance is magnetic force or magnetic force consequently as there's AN way over unbalanced positive spins or negative spins.  Substances like wood or air ar non-magnetisable as a result of in their case, the positive and negative lepton spins ar equal, thus they cancel one another out.