

712 Prof. E. Taylor Jones and Mr. D. E. Roberts on 



The curve representing the square of this expression is 

 shown in fig. 2, the corresponding photograph in Plate XII. 

 fig. 9, and a^ain there is close agreement in the form of the 

 curve. 



The maximum secondary potential (calculated) is 20085 

 volts, the observed value (by comparison with the curve 

 given by the air-core coil) 17250 volts. 



Case III. — The primary coil was placed fully inside the 

 secondary so as to give the maximum values of the secondary 

 self- inductance and the coupling coefficient. Owing to 

 sparking between the plates of the oil condenser this was 

 replaced by a ley den-jar. The constants for this case 

 were : — 



L 1 = '02303 henries. 



L 2 = 513 „ 



M = 3-197 



F =0-8643 



(^ = 15*95 microfarads. 



C 2 = -001051 „ 



R l5 R 2 as before. 



The ratio of the frequencies was considerably greater than 

 in the previous cases, their values being 



ni =-170-l, n 2 =908-8. 



With a primary current of 8*5 amperes the expression for 

 the secondary potential is 



2V 2 = 30090<T 6 ' 217 ' sin (61232*-0'55) 



-5610 e~ u *' 6t sin (327157*-2'9). 



The curve representing the square of this expression is 

 given in fig. 3, and the corresponding photograph in 

 Plate XI T. fig. 10. Though there are differences in detail, 

 in general form the resemblance between the two curves is 

 close, and there is also good agreement, in this as well as in 

 all the other cases, between the calculated and observed 

 values of t at which the potential is zero. The calculated 

 value of the maximum secondary potential is 31730, the 

 observed value 26500 volts. 



The greatest spark-length observed in this case between 

 two brass spheres, each 2 centimetres in diameter, was 

 8*5 millimetres. 



i! 



