Magnetic Induction in a Long Iron Bar. 



267 



From curves Q we can easily deduce the mean induction 

 by taking the area and base of the curves ; this is given in 

 Table II. under the heading B,„. The equivalent length of 



Ker. 5. 



1(3,000 



12,000 



10,000 



Values of H. 



the bar will be the same proportion of its actual length that 

 B OT is of B c ; this is also shown in the table. Half the differ- 

 ence between the true and the equivalent lengths will give the 

 distance of the resultant pole from the end; this is tabulated 

 under the heading D. 



From Table I. and the curve P the actual inductions can 

 be derived for the various points of the bar at any definite 

 value of H a ; if we can assume the annealing to have been 

 good enough to permit us to take the bar as being the same 

 under the two conditions (which is borne out by the close 

 approximation of the curves towards the maximum induction), 

 it is possible to deduce the distribution of H in tbe bar by 

 cross reading from curve R the value of the H for each value 

 of B at each point. Curves showing the distribution of H are 

 given in set S (fig. 7). From these the value of the mean H was 

 found as above described for B, and is tabulated under H w in 

 Table II. The induction this would have produced in the bar 



