798 



ELECTRICAL METHODS 



[Chap. 10 



When the loop is laid out on the surface of the ground {d = 0), Zq = 27r5iR. 

 Substituting the electrical density 27r%(ri , 



Z'q = 47r'/o<riR. (10-61c) 



Pamrylop f^^^ ^^^^^ ^"^^^ 



First Disk 



Fig. 10-114. Representation of magnetic fields of loops by potentials of disks and 

 disk images of equivalent densities. 



This is obviously the same as eq. (10-60a), differentiated with respect to 

 /. When the ground is not homogeneous, the same relation can again 

 be used for an apparent conductivity, so that, analogously to eq. (10-606), 



(Ta — 



47r3IoR' 



(10-61d) 



