A New Determination of the Ratio of the Electromagnetic to the Electrostatic Unit of Electricity [Part 2] Page: 541
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DEPARTMENT OF COMMERCE
BULLETIN
OF THE
BUREAU OF STANDARDS
Vol. 3 No.
A NEW DETERMINATION OF THE RATIO OF THE
ELECTROMAGNETIC TO THE ELECTROSTATIC UNIT
OF ELECTRICITY.
[Continued.]
By E. B. Rosa and N. E. Dorsey.
VII. DETERMINATION OF CAPACITIES IN ELECTROMAG-
NETIC MEASURE.13
In the electromagnetic measurement of the capacity two distinct
methods were employed, viz: (i) The method described by Maxwell; '
(2) the differential galvanometer method. For the latter method
connections were so made that we could readily measure either the
charging or the discharging current.
39. MAXWELL'S BRIDGE METHOD.
As is well known this method consists in replacing one of the
resistances in a Wheatstone bridge by a condenser and a suitable
device for rapidly and regularly charging and discharging the con-
denser. Maxwell originally suggested a periodic reversal of the ter-
minals of the condenser, but this is not so good, mechanically, as the
periodic charging and discharging by touching one terminal of the
condenser P(Figs. 29, 30) alternately to R and S. Then, by a suit-
able adjustment of the frequency of the charging, and of the magni-
tude of the resistances of the net, a balance of the galvanometer can
be obtained. When this is done the relation between the electro-
magnetic capacity and the resistance will be 15
13 We are under obligations to Dr. F. W. Grover and Mr. H. D. Babcock for assist-
ance in some of the experimental work, and to Mr. G. W. Vinal and Miss G. C. U.
McDermut for assistance in preparing the results for publication.
4 Electricity and Magnetism, Vol. II, ( 776.
'5 J. J. Thomson, Phil. Trans., 174; 1884. Proc. Roy. Soc. 35, p. 346; 1883. Rosa
and Grover, this Bulletin, 1, p. I53; 1905.
541
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Rosa, Edward B. & Dorsey, N. E. A New Determination of the Ratio of the Electromagnetic to the Electrostatic Unit of Electricity [Part 2], report, 1907; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc66541/m1/1/?rotate=90: accessed March 29, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.