490 Perkins — Rectification Effect in a Vacuum Tube. 



of the tube, and the zero at the center. To still further explain 

 the form of the experimental curve we have to consider that 

 the value of N obtained is proportional simply to the balance 

 of + charges left at A at the end of one cycle, but we have 

 taken no account of the conductivity of the tube itself which 

 it is necessary to consider if we are investigating the current 

 through the galvanometer. We must then introduce a factor 

 that takes account of the variation of the tube's conductivit} 7 , 

 or rather convectivity . Now it is clear that such a factor 



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 £f£Ctros?otrc 1/cffmefer 

 /orjjff/erenf TbsffwrrS 

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Curves from blotting 



/V-A'{tdYt-dXTroV-l')J, and 

 reduced to some scale. 



Curve cifo'rred' bu bfcttfrg 

 rV-/Ki/(l-d)],/or faff 

 of the fui>e. 



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 /V= A'(df/-dX7?vlf'-/V, 

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depends on the longer segment, and will be zero for all cases 

 when no ions are able to reach B during the time T. It is 

 further limited to that portion of the cycle in which the ions 

 are traveling in the right direction to conduct the current 

 indicated above. This is supplied by (3) only. Then, if 

 instead of regarding all 2m ions as available, we multiply N by 

 the factor that determines the proportion of 2m reaching B 

 during the second half cycle, we shall account for the limited 

 conductivity of the tube. Consider, as before, Kj as quite 



small, then (3) reduces to 



2 m 

 l + d 



T- 



KJ 2 



d and substituting 



this for 2m in the main equation we have 



