Conductors conveying Steady or Transient Currents, 241 



The energy sent per second through the sphere of radius p 

 with velocity " v," is 



. 



■ . - M KV* sin 2 8 







4 K^V 2 



3' 16c 2 



12/umP 



(U) 



And this is the rate at which the oscillator radiates energy 

 during its activity. Comparing (11) with (10) we see that 

 the equatorial radiation exceeds the mean radiation in the 

 proportion of 3 : 2. 



The difference of potential V is not constant, but decreases 

 logarithmically according to the law 



where R is a dissipation-coefficient of the dimension of re- 

 sistance, and of value easily found, thus: — 



Total energy radiated for every spark of the oscillator is 



I 



Vgjj ,. jSVp'.B 



UflVC 2 ' 12/JLVC 2 ' 



which must also equal |SY 2 , the initial energy ; hence 

 R=12/W=360c 2 ohms. 

 Taking as a numerical example the same oscillator as above, 

 with c = 4^ and V — 88 electrostatic units, all these values are 

 easily estimated. For instance the mean energy of the 

 radiation per unit volume at any considerable distance r, say 

 2 metres, in the equator, is 



KY 2 88x88 3-8 3-8 



32wcV " 25 x 81r 2 7 r 2 ~ 4 x 10 4 



= 95 microbarads, at a distance of two metres . 



This will cause a momentary pressure on a metallic surface 

 normally exposed to it, of 95 microdynes per square centimetre, 

 or a milligram weight per square metre ; and is nearly twice 

 as strong as full sunshine while it lasts. 



At 1 metre distance, I need hardly say, the energy and the 

 pressure are 4 times as great. 



The area of energy absorbed by a fine wire linear receiver 

 may be estimated roughly by rinding the closeness of a grid 



