134 Crook — ElectromagnetiG Alternating Currents. 



Two methods of stii dying the hysteresis were adopted, so 

 that the results of the one might be a check on those of the 

 other. 



First Method. 



The first method was a modification of the apparatus used in 

 the Hopkinson's bar and yoke method. The bar of iron, fig. 1, 



Fig. 1. 



was made up of eighteen strips of sheet iron, each 40^™ long, 

 l-9cm wi(je and *045^"' thick. These were joined at the ends, 

 and insulated from each other by strips of shellacked paper so 

 that a current would flow through each successive strip in the 

 opposite direction. Allowing a small amount for the effect 

 due to insulation between the iron strips, it was estimated that 

 the internal magnetic action of a current flowing through the 

 iron in the manner described above, was approximately one- 







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