198 Transactions. — Miscellaneous. 



When the weight reaches the lever C D it breaks the 

 secondary circuit Q E D R, and the remainder of the quantity 

 of electricity induced at break flows through the ballistic 

 galvanometer. 



By varying the turns of the screw— i.e., the interval be- 

 tween the break of the primary and secondary — the quantity 

 of electricity which has passed through the secondary during 

 the different intervals is easily determined. 



It must be noted that the galvanometer does not influence 

 the curve so obtained, as the deflection of the galvanometer is 

 proportional to the quantity of electricity which has passed 

 before the galvanometer is placed in the circuit. 



The duration of the induced current in the secondary is 

 dependent on the self-induction and resistance : the greater 

 the resistance the shorter the duration, and the greater the 

 inductance the more prolonged the duration. 



Let L and N be the self-inductance of the primary and 

 secondary circuits respectively, and M the coefficient of mutual 

 induction ; let R and S be resistances of primary and secondary ; 

 let X and y be the currents in primary and secondary : If 

 E be the E M F of the battery, the equation of rise in the 

 primary is given by 



and the equation of rise in the secondary 



N 



(]y , T\/r f^'^- 

 dt 



+ M-^--f S/y = 0. 



From these two equations x and y may be found when 

 L, M, and N are constants. When iron, solid or finely divided, 

 is in the circuit, the values of L, M, and N are variable, and 

 the values of x and y cannot be determined. 



The duration of the current in the secondary was deter- 

 mined under varying conditions of lamination of the iron, and 

 a few of the more important results are given. 



The duration of the induced current at break, when 

 there was no iron in the circuit, was first examined. Two 

 solenoids were wound over one another, and the secondary 

 was of sufficient number of turns to give a convenient de- 

 flection in the ballistic galvanometer when the current was 

 broken. 



Curve 9 (A) shows the quantity of electricity that has 

 passed in the secondary for different mtervals of time. 



Curve 9 (B) is the current-curve, and is deduced from 

 9 (A) ; for the current flowing in the circuit at any instant 



is given by C = — ~, w^here Q is the quantity of electricity 



that circulates in the secondary. 



