A New Determination of the Ratio of the Electromagnetic to the Electrostatic Unit of Electricity [Part 2] Page: 549
541-604 p. : ill. ; 26 cm.View a full description of this report.
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Rosa. ] Ratio of the Electrical Units. 549
Another advantage of this method is that the resistance in the
charge or discharge circuit is always rather small, being merely that
of the galvanometer coil g2, which is about 80 ohms. It is the same
whatever the capacity, so that the duration of contact of the brushes
in this method might be shorter, if desired, than in the bridge
method. However, they were always adjusted by the same criterion
as described on page 552.
The connections for the differential method are also represented
in Figs. 35 and 36, which are exactly equivalent to Figs. 33 and 34.
CONDENSER ",,
/,"
A c
b
Fig. 37.-Showing how the Maxwell Bridge Arrangement is Obtained by Rearranging the
Resistances and Galvanometer Coils of the Differential Method, Fig. 35.
To change the connections shown in Fig. 35 into the proper con-
nection for the bridge method we have only to (i) interchange the
battery and galvanometer (putting both halves of the galvanometer
in series) and (2) put the resistance d in the arm CB (see Fig. 37).
We now have a Maxwell bridge consisting of the same resistances,
and it will be balanced when a small change is made in a, corre-
sponding to the difference in the correction factors, Fin the one
case and I +A, in the other. This change is so quickly made that
it is very convenient to compare measurements by the two methods,
especially in the case of the spherical condensers where, owing to
the absence of a guard ring, a single bridge is used.
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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/m1/11/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.