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XXXVII. Note on the Measurement of Resistance. 

 By Dr. J. W. W. Waghoen*. 



IT is well known that an unknown resistance x can be 

 determined in terms of a known resistance R, if both are 

 arranged in series with a cell, and if the deflexions of an 

 electrometer be observed when connected in turn to x and 

 toR. 



If C is the current in the circuit, the differences of potential 

 at the terminals of x and of R are respectively Gx and CR. 



It is also well known that any voltmeter may be substituted 

 instead of the electrometer, if the resistance of the voltmeter- 

 circuit is very large compared to x and R. 



But it may not have been generally observed that the same 

 method may be employed whatever be the relative resistances 

 of the voltmeter and the conductors ; and is true even if the 

 usual conditions are reversed, so that the voltmeter-resistance 

 is very small compared to x and R. Any galvanometer may 

 take the place of the voltmeter. 





f 



R 



h 



Let G be the resistance of the galvanometer ; 

 E be the E.M.F. of the battery ; 

 r be the resistance of the battery and connecting- wires. 

 Let C be the strength of the current on the undivided part 

 of the circuit ; 

 Qx be the strength of the current through the galvano- 

 meter when its terminals are connected to x ; 

 Cr be the strength of the current through the galvano- 

 meter when its terminals are connected to R. 



* Communicated by the Physical Society : read February 23, 1889. 



