460-463] 



Physical Phenomena 



399 



We pass to the consideration of the way in which the magnetic coefficients 

 vary with some of these circumstances. As K and p are connected by a 

 simple relation (equation (391)), it will be sufficient to discuss the variations 

 of one of these quantities only, and the quantity /x will be the most con- 

 venient for this purpose. Moreover, as the phenomenon of induced magnet- 

 isation is almost insignificant in all substances except iron and steel, it will 

 be sufficient to consider the magnetic phenomena of these substances only. 



463. Dependence of fi on H. The way in which the value of //, depends 

 on H is, in its main features, the same for all kinds of iron. For small forces, 

 p is a constant, for larger forces /j, increases, finally it reaches a maximum, 

 and after this decreases in such a way that ultimately ^H approximates to a 

 constant value. This is represented graphically in a typical case in fig. 113, 

 which represents the results obtained by Ewing from experiments on a piece 

 of iron wire. 



^ 15000 



= 10000 



/i=3000 



= 2000 



H = 



20 



The abscissae represent values of H, the ordinate of the thick curve {the 

 value of pH, and the ordinate of the thin curve the value of /*. The corre- 

 sponding numerical values are as follows : 



