ELECTROSTATIC MACHINES. 68 1 



The charge of the battery in coulombs was therefore 



which is about 0-00002 coulombs for one turn. 



If the machine made 10 turns in a second, the current will 

 be 0*0002 ampere ; this is almost the result obtained by con- 

 necting the poles by a galvanometer, the wires of which are suitably 

 insulated. 



In the preceding case, the work utilised, U, is equivalent to the 

 discharge of the battery, which gives in kilogrammetres 



8 x 9 . 8 . 



The work utilised for each turn is then 0-0055 kgm., and it would 

 be twice as much if the difference of potential was constant. For a 

 velocity of 10 turns, the work per second will be 0*11 kgm. ; it would 



be about of a horse-power. 

 682 



The electrical work, however, which corresponds to the working 

 of the machine increases greatly with the striking distance. In 

 order to form some idea of this, we will suppose that the product 

 is constant, and that the poles are separated, so as to keep un- 

 changed the difference of potential which gives the maximum 

 striking distance; this was 22 cm., corresponding to about 133,000 

 volts. In this case the work per second, and for the same velocity 

 01 10 turns, will be - - - = 24-68 times as much ; it will represent 



! 5490 



then - of a horse-power. 

 27-6 



These considerations show that the energy utilised by these 

 electrostatic machines is really very small. It is observed that, with 

 reaction machines, the work of keeping up their motion increases 

 when they are primed ; but the greater part of the work expended 

 is absorbed in friction and in losses of electricity. 



