24
KINETIC ENERGY OF ELECTRICITY IN MOTION [I]
The logarithmic decrement in this experiment was λ = 0·4396,
and the corresponding factor 3.876/T: hence the reduced kick
was
238.67
T
Thus for the resistances of the bridge and the arrangement of
circuits used this kick corresponded to the mutual inductance
P'=37,840,000.
When the branches of the spirals were traversed in
opposite directions, the corresponding electromotive force of
the extra-current was for each of the spirals
P=178,500.
But we have to correct for the induction of the rest of the
bridge as follows:-
1. The self-inductance of each of the German-silver wires
(diameter = 0.246 mm.) is 12,790; twice this must be sub-
tracted, so that the correction is 25,580.
-
2. This action is in part compensated by the action of the
neighbouring German-silver wire. Their mutual inductance
is 5348; this value is to be taken twice, so the correction
is +10,696.
3. The self-inductance of the wire OP is + 9028.
4. The mutual inductance of the wire OP and the nearer
German-silver wire is +2789.
5. The same for the further one is - 1230.
-
6. The mutual inductance of RS and EA', taken twice
because of the double strength in RS, gives +5254. The
sum of all these corrections only amounts to +957, of which
one half goes
to the account of each spiral, namely
+478 mm.
Hence, finally, the inductive electromotive force is
measured by 178,978, which is almost exactly that due to
the spirals alone. The error in this value, due to neglecting
portions of the induction of the spirals, according to what
precedes, at most amounts to 2400 mm. The error due
to neglecting portions of the bridge will presumably be of the
same order.