i6o 



COEFFICIENTS OF INDUCTION. 



A and B are two equal coils with rectangular channels of 

 dimensions a, 2&, 2t, and n, the mean planes being at a distance 

 2X. A long coil A' with ri windings* a height h', a mean diameter #', 

 and a thickness 2c' is placed, so that its base is in the plane of 

 symmetry of the two coils A and B. 



The mean circle of this base is 



and the total mass of the equivalent magnetic layer 



n 

 - 





3 a 



A' 



Fig. 148. 



The mean action of each of the coils A and B on this base S 

 is from equation (39) of (740) 



F. 



2HTT 



putting 



i: 2 _ i 2 + 3^2 3.5*4 

 + ^~2~2-+ ^ + " 



_3_-LTl+^--^^ 3 4- 1 



2.2 2 2 1_ 2.3^2 2.3 a 2 "J 



3 2 -5 yr 5-6 ^ 2 5.7^ 2 + 3^ 2 I 



2.2. 4 2 4 L 2.^ 2. ^2 



