136 



DR. HAROLD A. WILSON ON THE ELECTRIC EFFECT OF 



the induced electromotive force in a conductor when moving in a magnetic field is 

 accurately known. 



The equation Q' = 



2067 X 25-4 



X (I K l ) Cn can be used to calculate K from 



3 X 10 10 



the experimentally-found value for Q'. It gives K = 3 '68, which is 4 per cent, 

 greater than the value found by measuring the capacity of the cylinder. 



The following table contains a comparison of the observed deflections with those 

 calculated by means of the theoretical formula 15'19 X 10~ 7 Cn = Q = 8r//S, where 8 

 is the deflection due to the effect, and S the electrometer deflection due to a charge q. 



(5.) Summary of Results and Conclusion. 



From the results of the experiments described above it may be concluded that : 



(1) A radial electric displacement is produced in a dielectric such as ebonite 



when it is set rotating in a magnetic field parallel to the axis of 

 revolution ; 



(2) The direction of this displacement is the same as that which would be 



produced in a conductor similarly situated ; 



(3) The displacement is proportional to the magnetic field and to the rate of 



revolution ; 



(4) The amount of the displacement agrees with that calculated on the assump- 



tion that an electromotive force is induced in the dielectric equal to that 

 in a conductor multiplied by 1 K" 1 , where K is the specific inductive 

 capacity of the dielectric. 



