Galvanometers by a Constant Current, 

 sin# 



31 



If and - — j^ be plotted, we get the calibration -curve for 

 that particular galvanometer (fig. 3). 



Fig. 3. 



«ifl 



4-5 

 4-0 

 3-5 

 3-0 





n 















2 5 

 2-0 

 1*5 











1*0 







0-5 













10 



20 30 40 



Values of 0. 



60 



In the foregoing Table the values of 6 are integral numbers 

 of degrees ; but this is not at all necessary, for no fine 

 adjustment, such as is required with sine-galvanometers, need 

 be attempted. All that is needed is that the position of the 

 needle, as indicated on the scale of the galvanometer, should 

 be accurately noted before breaking the circuit to observe the 

 corresponding D. 



The method described above may be utilized as a ready 

 means of testing whether a galvanometer, whose law is sup- 

 posed to be known, does actually conform thereto. For if the 

 law of the galvanometer is C =/(#), then, on plotting f(6) 



sin 



and -. — ™ a straight line should result. 



In the case of tangent-galvanometers, where f{6) = h tan 6 



