22
KINETIC ENERGY OF ELECTRICITY IN MOTION [1]
put in the circuit B, so that the actions of the spiral and of
the rectilinear circuit aided each other, and the action of the
one branch on the other was observed by simply reversing the
current B each time the needle passed through its position of
rest. After reduction to the strength 100 the inductive kick
was found to be
164.3, 164.7. Mean 164.5 scale divisions.
=
The corresponding decrement was λ= 0.6362, and the reduc-
tion to an unresisted needle gives the value of the kick
696.0
T
We may here and in what follows neglect the effect of
damping in altering the period. Hence the mutual inductance
of the branches of the spiral is to that of the rectilinear cir-
cuits in the ratio of
150
696.0-1.1 : 1∙1097 = 694.9 : 1·1097.
FIG. 5.
The latter inductance was
easily calculated from the
geometrical relations of the
wires, and was found to be
60428 mm., whence it
follows that the mutual
inductance of the branches
of the spiral = 37,840,000
mm.
the
I had already found for
same quantity the
value
38,680,000 mm.
by a different but more
uncertain method.
The two
values agree sufficiently
well, but we shall only use
the first one.
Execution of the Experi-
ments.—The arrangement of
the bridge used for measuring the extra-currents is shown in