Effects of Mechanical Stress on Electrical Resistance. 299 



Renewed Test on Copper Wire made after the Paper was written. 



This series was made in order to find if, after the wire had been 

 stretched almost to breaking and allowed to stand, there would be 

 any more permanent alteration of specific resistance due to renewed 

 application of weight. First of all, a series of stretchings was given 

 to the wire, as in the former tests of the same wire. Column 2 of the 

 following Table A was thus obtained, and will be found to agree very 

 well with column 2 given under "Tests of Copper Wire" in the 

 former series. 



This wire was then tested by applying successive weights, the 

 readings being taken with weight on and also after the weight had 

 been taken off. Columns (2) and (3) of Table B give the results of 

 these tests. Column (2) shows the ratio of the weight specific 

 resistance with the weight on to that before the weights were 

 applied for the second series. Column (3) gives the ratio with 

 weight off to that before the weights were applied. Column (2) 

 therefore shows the permanent and temporary alteration, and (3) 

 shows the permanent alteration. There was, however, still a 

 slight permanent stretching, which accounts for the small increases 

 shown in Column (3). The results showed that when there was no 

 permanent stretching application of weight only caused temporary 

 alteration of weight specific resistance. 



The numbers in columns (2) of Tables A and B when plotted on 

 curved paper, with (for A) percentage stretchings as ordinates, and 

 weight specific resistances as abscissae, and (for B) weights applied 

 as ordinates, give practically straight lines. This shows that the 

 permanent alteration of specific resistance is directly proportional 

 to the stretching, and the temporary alteration is directly proportional 

 to the weight applied. 



vor,. LIV. 



