190 



Transactions. — Miscellaneous. 



all passed through the ballistic galvanometer long before there 

 could have been any appreciable movement of the needle. 



The hysteresis curve for the very rapid cycle v?as deter- 

 mined for the same maximum values of induction as the static 

 curves, and under exactly the same conditions. 



dt 



10 15 20 25 30 35 40 45 50 55 



Curve 2 (A A) represents the relation between the values of 

 and t (time) for the soft-iron ring. 



Since "^ '■'■'• may be called the back E.M.F. in the circuit at 



any instant, when t = o, -^ = E, the total E.M.F. of the 

 battery. The value of the current flowing in the circuit at any 

 instant is therefore known when -rr is known. It will be 



observed that the value of -^ changes rapidly at the beginning, 



and then very slowly when the steep part of the hysteresis 



curve is reached. The value of -j- changes again very rapidly 



at the point where the hysteresis curve bends over, and gradu- 

 ally falls to zero as the iron reaches its saturation-value for 

 the maximum magnetizing force. 



Curve 2 (B B) is deduced from the curve A A. If we take 

 any point in the curve A, the magnetizing force is known, and 

 the value of the total induction through the iron corresponding 



, . , dw dn. 

 * In figures of curves erroneously printed as — or -^ 



