Magnetic Permeability of an Iron Bar. 



277 



quantity corresponding to the first cut ; the last column gives 

 mean values for the seven cuts by which the bar was finally 

 divided into eight pieces. It will be seen that the average 

 thickness of air-space in the later cuts has been greater than 

 in the first, probably because the first cut has happened to 

 produce flatter faces than the subsequent cuts. As the mag- 

 netizing force is increased, the thickness of the equivalent 

 air-space diminishes to a very marked degree*. 



Fiff. 2. — Effects of successive cuttings on the magnetic permeability 

 of a wrougkt-iron bar. 



No load 



Load of 226 kilogs. per square centim. 



irooo 











■ 







I 



1 















16000 



1 5000 













3s 

















B 



£ 



1400*' 

















HB 











9 







13000 









S6 

























12000 









H 







§ 



















x 11000 

































6 



v ~' 1000(1 





mm 































wm 



1 

























letic Inducti* 



> c 



1 <z 



> c 





11m 





m 



r gm 























Mi 



























S 



6000 



5000 



40 IK 

 3000 

































H 



m 



■ 



























U 



n 























































































2000 























■ 











1000 

































5 10 15 20 25 30 35 40 45 50 55 00 05 /0 Ji 



Magnetizing Force, <Q (C.6.S.). 



* The magnetic "resistance" of the joint may of course also be ex- 

 pressed as equivalent to so much length of the iron bar itself, this length 

 being found by multiplying the thickness of "air-space" by the perme- 

 ability of the solid bar, under corresponding values of *j. The numbers 

 in the last column, treated in this way, give from 41 to 2*2 millimetres 

 of iron as equivalents of the resistance of the joint. 



