PEIRCE. — CHANGES IN INDUCTANCES OF ELECTRIC CIRCUITS. 567 



Figure 27. 



diagram for the iron di- 

 rectly from the records 

 of an oscillograph in the 

 coil circuit. It is diffi- 

 cult, indeed, to obtain by 

 any method a satisfac- 

 tory magnetic curve for 

 such a core, for if the 

 iron starts from a given 

 magnetic state, it is 

 possible to get very dif- 

 erent magnetic fluxes 

 from a given exciting 

 current by building up 

 the current more or less 

 slowly. In any useful 

 examination of the mag- 

 netic properties of a solid 



^ 

 ^ 



(^ 



(D 



i] 



# 



(fi 



it 



-dtu 



qp cp 



Figure 28. The electromagnet TP which has 

 a soUd core weighing about 300 kilograms. 



piece of iron which is to be used for any practical purpose, it is essential 



