39 2 Note 1 6.- mutual influences of condensers 



The results obtained by Gordon*, who employed a break which gave 1200 

 interruptions per second, and those obtained by Schiller f by measuring the 

 period of electric oscillations, which were at the rate of about 14,000 per second, 

 are much smaller that those obtained by Cavendish and by Hopkinson. 



Hopkinson finds that the quotient of the specific inductive capacity divided 

 by the specific gravity does not vary much in different kinds of flint glass. As 

 Cavendish always gives the specific gravity, I have compared his results with 

 those of Hop*kinson for glass of corresponding specific gravity. 



Electrostatic capacity of glass. 



Flint-glass ......... 3-279 7-93 



Do., a thinner piece 3-284 7-65 



Light flint ......... 3-2 6-85 3-013 2-96 



Dense flint ......... 3-66 7-4 3'O54 3-66 



Double extra-dense flint ... 4-5 10-1 3 - i64 



Very light flint ...... 2-87 6-57 5-83 



Plate-glass ......... 2-8 8 6-10 6-43 



Crown-glass ......... 2-53 8-6 3-108 



NOTE 16, ART. 185. 

 Mutual Influence of two Condensers. 



To find the effect on the capacity of a condenser arising from the presence 

 of another condenser at a distance which is large compared with the dimensions 

 of either condenser. 



Let A and B be the electrodes of the first condenser, let L and N be the 

 capacities of A and B respectively, and M their coefficient of mutual induction, 

 then if the potential of A is I and that of B is o, the charge of A will be L and 

 that of B will be M , and if both A and B are at potential i the charge of the 

 whole will be L + zM + N, and this cannot be greater than half the greatest 

 diameter of the condenser. 



Let a and b be the electrodes of the second condenser, let its coefficients be 

 I, m, n, and let its distance from the first condenser be R. 



Let us first take the condenser AB by itself, and let us suppose that the 

 potentials of A and B are x and y respectively, then their charges will be 

 Lx + My and MX + Ny respectively. 



At a distance R from the condenser the potential arising from these charges 



Will \)(* 



{Lx + M(x + y) + Ny} R-i = P, 

 * Proc. R. S. Dec. 12, 1878. f Pogg- Ann. 152 (1874), p. 535. 



