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KINETIC ENERGY OF ELECTRICITY IN MOTION [I]
I have been able to find out only offer a hope of success if the
inert mass exceeds the limit here determined many thousand
times.
In conclusion, excluding the assumption last discussed, I
shall introduce the limit found for the quantity into the
calculations which have been developed by Helmholtz in vol.
lxxii. of Borchardt's Journal.¹ It is there shown, on certain
definite assumptions there stated, including the truth of Weber's
law, that in a conducting sphere of radius R certain types
of currents, of given order a, become unstable when in our
notation 2
R<a
μπ
2
From this and from the limit found for μ, viz. με 0.008 mm.,
it follows that on the assumptions made, the first, the funda-
mental, type-current would become unstable in a sphere of
0.11 mm. radius, and that in a sphere of 1 cm. radius the first
90 component currents, almost the whole current, might in-
crease indefinitely.
EXTRA-CURRENTS IN IRON WIRES.
If the wire conveying the current be capable of being
magnetically polarised, this circumstance will lead to an in-
crease of the self-induction like that due to any existing inert
mass of electricity; hence the magnitude of the capacity for
polarisation may be determined by the method we have
employed in attempting to discover the existence of electric
inertia.
In
I have made several experiments with iron wires, partly
to convince myself of the applicability of the method for this
purpose, partly to obtain an estimate as to how far magnetic
properties in other metals might give rise to disturbances.
these the resistance of the bridge under examination consisted
of a soft iron wire 0.66 mm. in diameter and 14,070 mm.
in total length. This, like the copper wire previously used,
1 H. Helmholtz, Wiss. Abhandl. vol. i. p. 589.
2 Our quantity μ is expressed by μ/2A in the notation there used.
M. P.
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SCIENCE ENGINEERING DE