II
37
INDUCTION IN ROTATING SPHERES
of the elect-
2. The calculations will be carried out in electromagnetic Definition
units.
In other respects the symbols for electrical magnitudes rical quan
will be those used by Helmholtz in vol. lxxvii. of Borchardt's tities."
Journal.
That is,
u, v, w
mgri
mm¹ sec
are the densities of the current parallel to x, y, z;
U, V, wmm¹ mgr¹
sec
are the corresponding components of the vector-potential;
mm mgr
φ
sec
is the potential of free electricity; 2
mm²
K
sec
is the specific resistance of the material. The specific resist-
K
ance of a sheet of infinitesimal thickness ♪, viz., will, when
considered finite, be denoted by
mm
k
sec
Further, let
mgr¹
λ, μ, ν
mm¹ sec
be the components of a magnetisation; let
L, M, N
mgr¹ mm
sec
be the potentials of λ, µ, v, taken as masses,
0(0)
1 H. Helmholtz, Wiss. Abhandl. vol. i. p. 545.
2 This is not electromagnetic measure. Measured in the latter units the
potential of free electricity is 4m-A3, where 1/A denotes the velocity of light.
The above unit avoids the inconvenient factor 1/A".