Manchester Memoirs, Vol. xlviii. (1904), No. 11. 



XL On a Suitable Arrangement for Determining the 

 Capacity of a Condenser by the Method of 

 Successive Discharges. 



By H. MoRRIS-AlREY, M.Sc, and E. D. SPENCER. 

 (Communicated by Dr. C. H. Lees.) 



Received and Read February i6th, igo^.. 



The necessity for having some quick and reliable 

 method for determining absolutely the capacity of a 

 condenser is well known, especially where the condensers 

 are used on alternating current circuits. 



The usual method given in text-books involves con- 

 siderable expenditure of time, and a sensitive ballistic 

 galvanometer is required, if accurate results are to be 

 obtained, and consequently Maxwell's method of succes- 

 sive discharges has been adopted in practice, with much 

 success.* 



The theory of the method may be briefly described 

 as follows : — 



We can regard capacity as the quotient 

 [Quantity of Electricity] 

 [Difference of Potential]' 

 This may also be written 



[Current x Time] 

 [Current X Resistance]" 

 Hence it should be possible to determine a capacity from 

 measurements of time and resistance alone. 



Imagine a circuit containing a battery of electromotive 

 force E, a galvanometer of resistance G, and a key Q.P.S. 



*Thomson and Searle, Phil. Trans., 1890, A, p. 583. 

 March 21st, 1^04. 



