34
KINETIC ENERGY OF ELECTRICITY IN MOTION [1]
consisted of two branches which could be connected up in two
different ways. The wire was again rectangular in form, so
that the self-inductance could be exactly calculated for both
arrangements. From the extra-currents obtained with these
two self-inductances it should be possible to calculate the
increase of self-induction due to magnetisation; in practice
this was found to be inadvisable, for the effect of magnetisa-
tion was not small but very large compared with the purely
inductive effect. Hence the iron wire was replaced by a
branch of one of the above-mentioned spirals with the neces-
sary ballast resistance, and the extra-current produced by
this known inductance was compared with that from the iron
wire.
The observations were made by the method above described:
their details are of no interest, but they supply the data from
which the magnetic forces acting in the iron wire and the
polarisations attained may be determined in absolute measure.
The results are given in the small table which follows. The
first column gives in absolute measure the values of the
magnetising force K at the surface of the cylindrical wire
(whence it diminishes towards the axis in proportion to the
distance from the axis). The second column gives the values
of 0, the so-called constant of polarisation, calculated from the
corresponding observations.
K
0
K
0.96
8.12
1.98
8.83
1.17
8.42
2.94
9.67
1.47
9.02
3.12
9.67
1.62
8.92
3.99
9.96
1.74
8.65
7.20
11.60
These values of K and can of course be only roughly
considered as corresponding values. Apart from several irre-
gularities, we see that increases with K within the limits
given, a phenomenon which has already been frequently ob-
served under different circumstances. It was impossible to
extend the observations to stronger currents, owing to the con-
siderable generation of heat in the iron wire.