342
Molesworth’s pocket-book
Electrical Formula, by Paget Higgs, LL.D,, C.E.—
continued.
E2
33. Rate of doing work — for a galvanic
element = 10’ for 1 volt through 1 ohm, or
1 volt-ohm uses gramme of zinc and does
107 absolute units of work per second. 1 EP = 746
volt-ohms, and is equivalent to the consumption
of grammes of zinc per second in a Daniell’s
cell, or 8J5 • 2 grammes per hour.
34. Potential at any point of a conducting
series: Let M N be the conductor length and X
an intermediate point. Let m and n be given
potentials at M and N, and x potential at X. If
r be the resistance between M and X, r1 between
X and N, and R between M and N = r + ,
r, m + r n
then x — -—-=------•
K
35. When a cable insulated at both ends is
charged by a battery, the potential of the charge
will be the same at all points of its length, and if
the two ends are put simultaneously to earth the
charges flowing out of them will be equal; and
since the flow is from the middle point of the
cable towards the ends, this point will keep its
potential a maximum above all other points in the
cable length. But with a cable charged with one
end to earth, the curve of fall of potential will be
a parabola, two-thirds of the charge returning to
the charging encl.
36. When a cable whose farther end is to earth
is charged by a battery whose resistance is small