tlie Maqnet'ic Erl'i'ct of Electric Correction. 



4-47 



Fig. 1. 







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IZ 





ZlB 



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2. ° 



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1 



These facts led us to study the duration and number 

 of contacts necessary to charge or dis- 

 charoe a condenser completely. A cylin- 

 drical rod T (tig. 1) of ebonite, 120 cm. 

 long, was placed vertically in such a 

 manner that a brass ring B, 1 cm. high, 

 could fall freely along T. At 10 cm. 

 above the lower end of the rod were 

 placed two metallic brushes, C and D, 

 opposite each other. The brass ring, B, 

 in falling made contact between C and D 

 for any desired interval of time, depending 

 upon the length of the drop. The con- 

 denser employed was the same as that put 

 in parallel with the disks. The source of 

 electricity Avas the high-potential battery 

 of M. Bouty, the capacity of which can be 

 considered infinite in comparison with that 

 of the condenser. 



The experiment was made as follows : — 

 First was measured the potential of one 

 pole of the battery when the other w^as 

 earthed. One plate of the condenser w^as connected to 

 the earth and the other connected to the brush D. The 

 brush C could be connected either to the free pole of the 

 battery or to the earth. First, let C be connected to the 

 battery, and let the ring fall; contact will be established 

 between C and D as the ring passes. The duration of the 

 contact could be varied between yq and -qV of a second. 

 After the fall the potential communicated to the condenser 

 was measured by an electrometer connected permanently 

 thereto. Under these conditions, w^e observed the fol- 

 lowing : — 



1. The potential assumed by the condenser was always 

 inferior to that of the battery. This difference was inversely 

 proportional to the time of contact and directly proportional 

 to the capacity of the condenser. 



Next, the condenser was charged by a prolonged contact 

 with the battery, and then insulated ; C w^as connected to 

 the earth, and the ring B dropped. The electrometer con- 

 nected with the condenser then indicated if the condenser 

 retained a charge after contact. We observed the following: — 



2. The condenser always retained a residual charge, the 

 value of which was directly proportional to the capacity 

 of the condenser and inversely proportional to the duration 

 of the contact. 



However, the difference between the potential of the battery 



