738 On the Self-Demagnetizing Factor of Bar Magnets. 



as those for the bars of circular section. Rectangular rods 

 of the softest Swedish iron of various proportions were pro- 

 cured, and reduced by milling-cutter to the required form, 

 so as in every case to have a sectional area of 1 square centi- 

 metre ; the ratios of breadth to thickness being respectively 

 1:1; 2:1; 4:1; 6 : 1, and 10 : 1. From each of these 

 rectangular rods pieces were cut of lengths of 10, 8, 6, 5, 4, 

 and 3 centimetres respectively. In all 35 different ones 

 were examined. For each of these a ^-^tf curve was plotted ; 

 and the self-demagnetizing-factors were deduced as before. 



In figs. 3, 4, 5, 6 , 7, and 8 these various curves are 

 plotted ; and in .fig. 9 the final results are summed up by 

 plotting the several demagnetizing-factors as functions of 

 X the ratio of the length to the square-root of the area of 

 section. 



Table II. gives numerically the values of the self-demag- 

 netizing factors obtained for various ratios of breadth b to 

 thickness t of the cross-section, and also for various values 

 of X. The individual bars were carefully gauged for breadth 

 and thickness, and the slight discrepancies (never exceeding 

 1 per cent, of the intended ratio) were allowed for ; but 

 being small they occasioned no difference in the plotting. 



Table II. — Demagnetizing Factors for Bars of different 

 lengths and equal Sectional Area, having Rectangular 

 Sections from 10 : 1 to 1 : 1. 



1 



Va~ 3 ' 



I 



vi~ 5 - 



-4-a 



-/A 



I 

 V A 





b/t. 



N. 



b/t. 



N. 



b/t. 



N. 



b/t. ! ]\ t . 



b/t. 



N. 



0-2358 



b/t. 



N. 



10-03/1 



0-828 



10/1 j0-586 



10-05/1 



044 



10/1 0-354 



10-2/1 



10/1 



0-178 



5-95/1 



0-925 



5-96/1 ,066 



5-99/1 



0-488 



6/1 



0-3885 



5-96/1 



0-264 



5-99/1 



0-19 



3-98/1 



1-02 



3-99/1 0-726 



3-98/1 



0-528 



3-96/1 



0415 | 



4/1 



0-28 



3-98/1 



0-206 



2-0 /l 



1-098 1 



2/1 



0-775 



2/1 



0-575 ! 



2/1 



0-448 i 



2/1 



0-3 



2/1 



0-22 



1-492/1 



113 



1-5/1 



0-7980 



1-49/1 



3-59 



1-5/1 



0-4645 



1-5/1 



0-3075 



1-495/1 



0-224 



0-9914/1 



113 



0-99/1 



0-8 



0-993/1 



>59 



0-996/1 



0-465 







0-993/1 



0-224 



It will be noticed that the Table records values also for bars 

 having the ratio of 1*5 : 1 ; but no curves are given for this 

 ratio, as they were practically the same as those for square 



