I
23
KINETIC ENERGY OF ELECTRICITY IN MOTION [I]
greater detail in Fig. 5. The current enters at A and A';
the galvanometer is connected at B and B. The bridge is
adjusted by moving the connection A' of the battery with the
thick copper wire EF. The spirals are inserted in the diag-
onally opposite branches A'B and AB, the passive German-
silver resistances are placed in the other two branches and lie
close together side by side, with the currents flowing through
them in opposite directions. The wires from the battery and
those to the galvanometer pass through the commutator G,
which is placed so that the observer can set it in motion
while observing with the telescope H. In every one of its
revolutions 20 double extra-currents from each of the two
spirals, in all 80 simple extra-currents, pass through the galvan-
ometer. The tangent galvanometer is at I and is read by the
telescope K.
The value of the extra-current was first determined when
the branches of the spirals were traversed in opposite direc-
tions. The following values were obtained :—
Strength of Primary Current
in Scale Divisions.
48.8
50.0
123.2
122.2
Strength of Secondary Current
in Scale Divisions.
0.1790
0.1738
0.4621
0.4417
By reduction to strength 100 we get the values
0.3664, 0.3476, 0.3750, 0.3600. Mean = 0.3622.
was λ =
The logarithmic decrement of the needle for these experiments
0.0172. If we therefore multiply the above kick by
the factor 3.168/T, we get the reduced value
1.1476
T
In accordance with previous explanations, one of the
branches of one spiral was next thrown out of circuit; the
bridge was readjusted, and the inductive action of the detached
branch on the other was observed. When in the former a
current 100 ceased to flow, the kick observed in the galvan-
ometer was
61.50, 61.66. Mean 61.58 scale divisions.
=