168 Potential generated in a High-tension Magneto, 



and by (28) the amplitudes are (with i =l ampere) 



B = 2^(L 1 +L 21 )» », ^ = g680 yolt 

 w 2 — nf 



B ML, + L,,) nfo =1950 



Further, 



^ 1 = 5r- LiCi = 4 ' 29 - 10 " 6 ' 



2 =^.L 2 C 2 = 1-63.10-e. 



Hence by (33) 



P= -2-187. 10" 6 , 



and b ^ (31 ) h = 1380, 



h = 4120. 



The expression for the secondary potential is therefore 

 (in volts) 



Y 2 = 8680 e~ 1S80t sin 938500^-1950 e~ imt sin 4185000*, 



t being in seconds and the angles in degrees. 



The phase angles 6\, S 2 are here neglected. They are 

 small, and being approximately proportional to the fre- 

 quencies their effect is merely to alter slightly the time 

 at which the maximum potential occurs without altering its 

 value to any appreciable extent. 



The maximum value of V 2 is 8530 volts at £=0"000069 sec. 

 (0 = 64° 45'). 



If damping had been neglected the maximum would have 

 been 9710 volts at t — 0-00007 sec. If, further, the circuits 

 had been better adjusted, so that the positive maxima in the 

 two oscillations occurred simultaneously, the maximum would 

 have been (for the same amplitudes) 10,630 volts. 



We may therefore say that there is a drop of 9 per cent, 

 in the maximum secondary voltage due to difference of 

 phase, and a drop of 12 per cent, due to damping. 



Now the least current observed to produce a 0*2 mm. spark 

 was 0'232 ampere. Taking the sparking potential at 0'2 mm. 

 as 1550 volts, the smallest primary current required to give 

 this spark is, according to the above expression for V 2 , about 

 0*182 ampere. The actual potential generated by the magneto, 

 as estimated from the spark-length, therefore falls short of the 

 value calculated by the above expression by about 25 per cent. 



