as Radiators in Wireless Telegraphy. 681 



(L) was 310,740 cms. Hence the inductance o£ the coil 

 itself of 5 turns was 259,830 cms. The inductance of the 

 two coils each of 5 turns in parallel was 198,350 cms., and in 

 series 779,300 cms. 



The inductance of each of the small or 2-foot square coils 

 was in the same manner found to be 116,200 cms. 



In series with these coils was placed a condenser having 

 a capacity (C) of 0*0026 mfd. and the coil and condenser 

 shunted across a 400-volt Poulsen arc. 



The arc current was generally about 8 amperes, the 

 potential difference of the arc terminals (V ) 260 volts 

 (continuous). The potential difference (Vj) (R.M.S. value) 

 of the condenser terminals was 1580 volts as measured 

 by an electrostatic-voltmeter and the R.M.S. current (a) in 

 the square coil was 4*22 amperes as measured by a hot-wire 

 ammeter. The frequency N of the oscillations is given by 

 the formula N = (5*033 X 10 6 )/ VCL. Hence if = 0*0026 

 mfd. and L = 310740 cms., we have N = 177,100. If the 

 R.M.S. current (a) in the coils were strictly sinoidal in wave- 

 form, the value should be calculable from the formula, 



where V= </Y 1 2 —Y<?= V(1580) 2 -(260) 2 = 1560 volts. 

 Hence we should have 



44 26 

 a= — x -jo xl560x 177100 = 4*52 amperes. 



The actual measured value was 4*22 or 7*3 per cent, less, 

 which may be accounted for by the known fact that the actual 

 w r ave-form of the current in the coil is not by any means truly 

 sinoidal. 



The wave-length X corresponding to a frequency of 

 177100 is nearly 169,000 cms., or rather more than 1 mile 

 in length. 



The total area S of the large coils using the 5-turn 

 circuit is 5 x (243*2) 2 cms. =295,731 sq. cms, and the value 

 of S 2 a 2 is therefore (295731) 2 x (4*22) 2 = 156 x 10 10 . Also 

 (177100) 3 = 554523 X 10 10 . For a closed square radiator the 

 energy in ergs radiated per period is given as already men- 

 tioned by the expression 



E = 10-4^. 



