﻿202 



Mr. A. Russell on the Dead Points of a 



The following table gives the modified values in feet for 

 the deflexions when the break occurs after the 1st, 2nd, . . . 

 7th pole, counting from an anchor-pole : — 



Deflexion of. . 



1st 



2nd 



3rd 



4th 



5th 



6th 



7th 



When 01= \ 



•40 















2 



•27 



•61 













3 



•17 



•38 



•70 











4 



•10 



•23 



•42 



•73 









5 



•06 



•14 



•26 



•44 



•74 







6 



•04 



•08 



•15 



•26 



•45 



•75 





7 



•02 



•05 



•09 



•16 



•27 



•45 



•75 



Pole. 



Also we give below the maximum deflexion liable to be 

 caused by breakage of 1, %■?"• . 6 wires, the point of break 

 being distant from both fixed ends. 



No. of Wires broken. Deflexion. 



1 -036 feet 



2 -084 



3 -151 



4 -251 



5 -419 



6 -752 



XXIX. Tlie Dead Points of a Galvanometer Needle for 

 Transient Currents. By Alexandee Russell, M.A., 

 MJ.E.E* 



THE effects produced by an alternating magnetic field on 

 a magnetic needle suspended in it have been studied 

 by several physicists f. The phenomena have been shown to 

 be amenable to calculation in certain cases, and have been 

 employed by RayleighJ to measure the power factor in 

 alternating-current circuits. 



* Communicated by the" Physical Society: read May 11, 1906. 



t Lord Rayleigh, Brit. Assoc. Reports, 1868 ; see also ' Scientific 

 Papers/ vol. i. p. 310, and vol. ii. pp. 401 and 579 ; A. Schuster, "Ex- 

 periments on Electrical Vibrations," Phil. Mag. [4] vol. xlviii. (1874) ; 

 Of. Chrystal, " On Bi- and Unilateral Galvanometer Deflexion," Phil. 

 Mag. [5] vol. ii. p. 401 (1876). 



% Lord Rayleigh, " On the Measurement of Alternate Currents by 

 means of an Obliquely Situated Galvanometer-needle, with a Method of 

 Determining the Angle of Lag," Phil. Mag. [5] vol. xliii. p 343 (1897) ; 

 or ' Scientific Papers,' vol. iv. p. 299. 



