On Current Curves. 261 



I ohm. The impressed E.M.F. is 12'5 volts. The periodicity is 

 slow, being 6 cycles per second, and the true periodic curve is seen 

 to appear before the end of the first half period. Curve A is calcu- 

 lated with the preliminary supposition that i = when t = 0, and 

 Curve B on the assumption that i = when pt = 0, neither of which 

 is strictly correct. 



Fig. 3 gives the (B, H) curve, and Table III the observations 

 upon which it is based, of the iron core under consideration. 



5. The method of this paper can be applied to the pre-determination 

 of the curves of the primary and secondary currents in transformers 

 and of the curve of magnetic induction with regard to time* 



[For, when there is supposed to be no magnetic leakage in the 'core, 

 the expressions for the primary and secondary currents are 



; (16)f 



,(17), 



_ 

 * 



tan = 

 D = 



ni 8 RS 



R being resistance of primary. S that of secondary, wi the number of 

 primary turns, % the number of secondary turns, L the self-induction 

 of the primary. 



From (16) and (17) H,the total magnetic force on the core (being 



reduces to 



where C = 



Now equation (18) treated in the same way as (15) gives the 

 simultaneous values of H and t. that is, of m and t. These latter 

 substituted in (16) and (17) give the simultaneous values of x and t 

 and y and t. 



