DISC FRICTION 

 SERIES B. 1,175 revolutions per minute. 



183 



SERIES C. 1,050 revolutions per minute. 



In addition to these, a number of experiments by Dr. W. C. Unwin 

 on a disc having n = 1*85 are available. These are as follows : 



For the sake of comparison the whole of the foregoing results have 

 been plotted in Fig. 94 against the curves representing the relationship, 



Resistance at t F. = Resistance at 65 F. X | j * . |^-| * 



for corresponding values of n. From these it appears that the theoretical 

 curves fit the experimental results remarkably closely, quite sufficiently 

 closely indeed to justify the adoption of this formula. 



To render the series more complete the theoretical curves for n = 1*9 

 and n 2'0 have also been added. 



The results show that the resistance diminishes with an increase in 

 temperature, the amount of the variation with a given temperature- 

 difference increasing as the temperature diminishes and also as n 

 diminishes. Its value in the neighbourhood of 65 F. with a polished 

 brass disc (n = 1*8) is about one- third of 1 per cent, per degree Fahr. 

 When n =1'9 this falls to one-seventh of 1 per ent. per degree Fahr., 

 and when n = 2'0 it becomes inappreciably small. 



