314 On the Forms of the Lines of Electric Force. 



The equation to the lines of force is 



dr ir\/ z 



. (Iirz tt\ 



an 



2ttz 



(25) 



2 log r= log sin— — |- const. 



A. A, 



The equation to the lines of flow comes out 



27TZ 



2tt 2 



logsin(^-|). 



Fig. 4. 

 >- 



(S6) 



(27) 



These curves are shown on flg. 4, beginning, in this 



20 40 60 80 100 120 140 160 180 



AXIS0FWI8E 



case, from the axis of the wire. It may be noted that if 

 we plot one line of force the others are got simply by 

 extending proportionally the ordinates measured from the 

 axis. 



In this case the magnetic force vanishes along with the 

 longitudinal electric. The energy-flow is backward and 

 inward from 0° to 45°, and forward and inward for the 

 remainder of the half wave-length. The exaggeration of 

 the diagram in this case consists hr making the radius of 

 the wire much too great in comparison with the wave-length, 

 in order to get room to show the trend of the curves. 



Queen's College, Belfast, 

 20th June, 1902. 



