216, 217] 



Images 



189 



Thus we may say that the image of a uniform field of force of strength F 

 is a doublet of strength Fa 3 and of direction parallel to that of the intensity 

 of the uniform field. 



The potential of this doublet is 



Fa? cos d 



r 2 ~' 



and that of the field of original field of force is Fx + C, 



FIG. 63. 

 or, in polar coordinates, 



- FT cos + C, 

 so that the potential of the whole field 



- + C 



.(126). 



FIG. 64. 



