60 On some Electromagnetic Experiments ivith Open Circuits. 



where 



2 _ M 



p C^LM-N 2 )* 

 The equation to determine p in the most general case was 



It is evident that this equation in p 2 has one root greater 



M 



and one root less than ~ /T 1 , T AT9N , the value when the cir- 

 Cj(LM— Wy 



cuit (2) was closed; and it is evident from the equation that 



if we diminish C 2 , the capacity of the condenser, (2) we 



increase one, at any rate, of the roots of this equation. 



Now, if the process of magnetization requires a time at all 

 comparable with the period of an electrical vibration in the 

 coil, so that we might expect the magnetization produced by 

 an oscillating current to get less as the time of oscillation ap- 

 proached the time required for magnetization, then the effect 

 of diminishing the capacity of the condenser in the coil (2) 

 would be to diminish the magnetization produced in coil (1). 

 For the effect of diminishing C 2 was, as we saw, to shorten 

 the shortest of the periods of vibration, which, if the above 

 hypothesis be right, would have the effect of diminishing the 

 magnetization due to this part of the current x ; and as we 

 proved the coefficient of the term of shortest period in x was 

 the greater, the greater part of the energy would be due to this 

 term. Thus the effect would be to diminish the magnetizing- 

 power of the coil. 



This corresponds to the experiments described if the coil (1) 

 refer to the secondary circuit, and the coil (2) to the coilEF. 

 When the coil EF has its ends attached to the plates of a con- 

 denser of large capacity, C 2 is very large; but when it is open, 

 C 2 is equal to the electrostatic capacity of the coil itself, which 

 will probably be very small comparatively. Thus the effect of 

 disconnecting the ends of EF from the condenser and leaving 

 them free, is to decrease very greatly the value of C 2 . This, 

 according to the reasoning just given, ought to diminish the 

 magnetizing-power of the secondary: a reference to the result 

 of the experiments will show that it actually did so to a very 

 large extent. A similar explanation will explain why the 

 magnetization ought to be greater when EF is closed than 

 when it is open. 



The above experiments were made in the Cavendish Labo- 

 ratory, Cambridge. 



i 



