THE METHOD OF CURVED ELECTRICAL PROBES 225 



ance q are determined by the expression; 



r9 



E^ 



Am 



2oz\R^+— ^+RAB cos e 



EB = - ^^ 



JR2 



271 1 R^+^ RAB co^ e 



Bearing in mind that 



/^4 Ti^ATv ^5 sin 9 



cos {E^, MN) = 



■'V 



cos (EB, MN) = 



R^+^+RABcos0 



4 



ZB sin 



V' 



21/ R^+-^-RABcos0 



we obtain according to (1) 



, .B lQABMNsm0{[^, AB'- ^—^ ^Y^'' 

 AUmn=~ 7 \\R^+—^+RABcose\ + 



+ \r^ + ^^-RABcos0 



\ 



From the expressions for the difference in potentials we transfer to an 

 expression for the coefficient of the arrangement, representing the latter 

 in the form of the product of two factors 



K = K*A. (2) 



The factor K* is calculated from the formula* 



ABMN ^ ^ 



and the factor A from the formula 



4 = __ __ :^3= ^::^ . (4) 



sin(9/ AB^ AB A^''' /, AB^ AB ' ~^'" 



To facilitate the calculations Ave will use a special nomogram for the 

 factor A, shown in Fig. 3. 



* The ibrmula is given for the case where the current is determined in amperes and the 

 potential difference in millivolts. 



Applied geophysics 13 



