Intelligence and Miscellaneous Articles. 531 



ON THE THEORY OF MAGNETIZATION. 

 BY PROF. DR. WASSMUTH. 



The lecturer iirst of all develops two new formulae for Poisson's 

 theory of magnetization by means of an equation of Green's. If h 

 is the magnetizing number, Y the inducing, Q the induced, and 

 V + Q=0the total potential, he obtains the equations 



7 l 



d - 



(l+4ir*)Q* = * fas-^ds + Jc f~ 

 J dm J r dn t 



I 

 r d- 

 Q i +4irJc(l>i=7cl< f _Lds, 

 J dn \ 



and _ , I 



a - 



which formulae may in some cases be advantageously employed 

 along with the usual one, 



n_7 r^ s ^ 

 Q J 7^-; 



It is thus shown how simply all the known methods of approxima- 

 tion for the problem of magnetization (Beer, C. Neumann, Eiecke) 

 may be deduced from these equations, and therefore also the 

 corresponding series. 



It is next investigated in how far the introduction of the idea 

 " magnetic resistance," at any rate in a special case, is justifiable. 

 With this view is treated the magnetization of an incomplete 

 ring, one, that is to say, which has an air-break, and is wound uni- 

 formly and completely with wire. By the aid of a strongly con- 

 verging series, the following expression is obtained for the number 

 N of lines of force with a close approximation, 



N= _ 47rS * 



+ 



/2irh l\ X 



where i is the strength of the current, s the number of all the 

 windings, Z the mean length and E 2 7r the section of the ring, A the 

 length and E 2 7r the section of the air-break, and K=l-j r 4rrk the 

 coefficient of magnetic permeability. In the denominator there is 

 actually along with the magnetic resistance of iron a sum which is 

 proportional to the ratio " length : section of the air-break," and 

 which can be taken as magnetic resistance of the air-break. But 

 this calculation shows us also that the factor with which this 



ratio ^.--appears multiplied differs from unity, by which what is 



Xl~7T 



called " the dispersion of magnetic lines of force " finds an explana- 

 tion. — Abstract of a Lecture given to the Natur. med. Verein in 

 Innsbruck. Communicated by the Author. 



