40 



RESEARCHES ON 



II. 



Time, fifteen minutes j^ast nine o'clock. 

 Tm-ns of rheostat ..... 

 Galvanometer of the circuit . 

 Deviation of the needle . . . . 

 To find this last deviation we proceeded thus — 



Position of equilibrium of the needle — pole 



Direct current (N. pole deviating E.) — pole -; 

 Inverted current (N. dev. W.) — pole 



9.00 



31° 05' 

 . 24° 59' 



J S. 6° 50' 

 iN. 181° 15' 



S^ 31° 00' 



N. 207° 30' 



Hence for the deviation E. 



Common mean E. 



For the deviation W. . 



f S. 343° 05' 

 t N. 155° 30' 

 r N. = 26° 15' 

 1 S. = 24° 10' 



= 25° 13' 

 r N. = 25° 45' 

 I S. = 23° 45' 



Common mean W. .... = 24° 45' 



Mean of both E. and W. . . . = 24° 59' 



N. B. In practice, without exceeding the limits of errors, we can take 25° for the 



value of d, because fractions smaller than itla of a degree could not be appreciated 



in such a small circle but by estimation. 



Determination of the constant Resistance of the Circuit. 



Divided current — galvanometer 24° — rheostat 

 Not divided current do. " 



Constant partial resistance r^ (^) . 

 Adding the galvanometer resistance g 



Constant resistance ..... 



TUKNS. 



11.00 

 70.00 



= 59.00 

 = 1.25 



= 60.25 



For the Determination of the Force on the Vertical Diameter of the Circle, c?= 25°. 



First Series. 



Position of the 



Beading of the 



Total resistance. 



Ratios of 



needle. 



rheostat. 





resistances. 



centre. 



19.00 



70.25 



1. 



2 tenths. 



12.75 



73.00 



1.037 



4 " 



19.50 



79.75 



1.121 



6 " 



37.00 



97.25 



1.384 



7 " 



56.00 



116.25 



1.655 



8 " 



94.55 



154.80 



2.203 



9 " 



205.70 



265.95 



3.785 



centre again. 



11.20 



71.45 



1.00 



9 tenths. 



202.70 



262.95 



3.680 



(*) The resistance of the deviating wire is equal to that of the galvanometer. 



