It is stated therein that the effect of ground conductors may
be notably increased by the division of the earth plates and the use
of metallic rods, without necessitating a greater output of material.
These facts, however, have not as yet been put to profit in practice
for the reason, perhaps, that the considerations, which have remained
general, have not at once permitted of obtaining forms what could be
employed with perfect knowledge of the results. This is what led Mr.
Ulbricht, of Dresden, to make calculations for a few forms of
conductors, and to test their approximate values. The results of these
researches are printed in the _Elektrotechnischen Zeitschrift_ for
1883 (p. 18).
[Illustration]
The equations found show, in the first place, that there exist three
means of obtaining a considerable effect, as regards the ground
conductor, with a slight expenditure of material: The cylindrical
electrode may be drawn out into the form of a bar or wire; the plate
may be rendered narrow, and elongated in the form of a ribbon; and,
besides, the annular plate may be enlarged in lessening the metallic
surface.
Finally, a short, open cylinder with a vertical axis may be formed by
curving a narrow plate or ribbon. It is not necessary to see the
formula to recognize the fact that this cylinder must behave like a
ribbon and a flat ring. The radius increasing, and the surface
remaining constant, the resistance of the earth here likewise
approaches zero.
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