Effect of a Changing Magnetic Field. 



475 



capacity, scale distance, and moment of: torsion of the 

 upper suspension are the same as in the foregoing specimen 



set. 



B x . 



E 2 . 



2d. 



2d'. 



L. 



L'. 



Per cent. 















error. 



600 



•345 



116 



3-34 



•33 



•26 



-21 



006 



•342 



2-70 



5-72 



•33 



•35 



+6 



006 



•490 



1-29 



2-13 



•47 



•45 



-4 



600 



•492 



•73 



1-24 



•47 



•44 



-6 



956 



•346 



•65 



102 



•52 



•48 



-8 



9D6 



•348 



2-06 



3 36 



•525 



•46 



— 13 



806 



•444 



1-59 



224 



•565 



•53 



— 7 



772 



••485 



101 



1-33 



•59 



•57 



-4 



828 



••490 



1-13 



134 



•04 



•63 



-2 



840 



•494 



•53 



•62 



•655 



•64 



—2 



848 



■495 



•65 



•73 



•66 



•67 



+ 1 



864 



•485 



127 



1-31 



•66 



•73 



+ 10 



916 



•490 



2-39 



2-70 



•71 



•b6 



-7 



956 



•474 



1-43 



1-53 



•716 



•70 



-2 



956 



•490 



•87 



102 



•74 



•72 



— 3 



956 



•492 



1-78 



1-86 



•74 



•72 



- 3 



1294 



•480 



•45 



•32 



•98 



1-05 



4-7 



1314 



•498 



•40 



•29 



103 



1-04 



+ 1 



Av. L' 3 per cent, too small. 



Conclusion. 



Considering the experimental difficulties involved, the form 

 of apparatus used, and the smallness of the force measured, 

 the accuracy of the foregoing results is all that could be 

 expected. The observed moment shows a decided tendency 

 towards lower values than the calculated amount. This is 

 possibly due partly to the effect of the magnetic field on the 

 charging current, partly to a phase difference other than 90° 

 between the electric and the magnetic field. These are the 

 only two sources of error not eliminated by the method of 

 observation, and since both act in the same direction of 

 diminishing the observed deflexion, the sum of their effects 

 is shown by the results to be only about 3 per cent, of the 

 quantity measured, which is not far from the probable ex- 

 perimental error. This can hardly be considered as casting 

 any doubt upon the result. However, an attempt will be 

 made to determine the phase difference, so that it can be 

 taken into account in the calculation. 



The experiment as it stands shows that a charged body in 

 a changing magnetic field, or perhaps more exactly in a held 

 swept by magnetic lines of force, is subjected to a mechanical 



