the Winding of Voltmeters. 109 



This equation cannot be solved generally, but by giving 

 various values to a we can find which of these values makes 

 the expression on the left-hand side most nearly equal to 

 nought, and to ascertain the value of the function for each of 

 the values of a we can conveniently use the curve connecting 

 0(a) and a previously employed. 



For a = 0*5 we have 



0(l) + 0(-O-5)-20(O) = l'375 + O-865-2xl-O4 



= +0-16; 

 for a = 0'4 we have 



0(1-2) + 0(-O«4) -20(0-4) =1-43 + 0-9-2 x 1-182 



= -0-034; 

 for a = 0'3 we have 



0(1-4) + 0(-O-3)-20(O-8) = 1-48 + 0-936-2 x 1*311 



= -0-206; 

 for a=0*2 we have 



0(l-6) + 0(-O-2)-2cf)(l-2) = l-53 + O-97-2 x 1-43 



= -0-36. 



0-2 





Fig 



2. 





















2 m 















z o-i 



in 



G 















"08 



w 



<u 















O 















1 -o-i 















o 

 O 



|3 















'■& 



a 



<u 

 u 



EH -0-2 















A 













o 



DO 

 0) 



-3 -0-3 























_n-A 













0-4 



Values of a. 



Plotting these points, we find (fig. 2) that the curve for 



