Potentiometer on Alternate Current Circuits, 



411 



The dynamometer D is not provided with a scale, but with 

 a fiducial mark which can be slightly adjusted t3 suit the 

 standard cell-check. It will also be made astatic to avoid 

 risk of error from stray fields. 



Fijr. 5. 



This apparatus should be capable of giving very good 

 results. In the meantime the results already obtained appear 

 to justify the belief that this method is capable of being used 

 with considerable accuracy and convenience for all P.D., 

 current, and phase measurements. 



The numerous applications of such an instrument are 

 obvious, and include P.D., current, phase, and power mea- 

 surement over almost any range : inductance and capacity 

 tests, and determination of dielectric losses, &c. One of the 

 most valuable applications, however, is to search-coil work 

 with alternate current^, whereby the distribution of main 

 and leakage fluxes in cores, and the propagation of magnetic 

 impulses can be studied. The variation of current and P.D. 

 along a cable fed with alternate 1 currents could also be 

 obtained. 



The writer's thanks are heartily tendered to Mr. A. C. 

 Jolley for setting up tne apparatus and great assistance in 

 the experiments. 



