Dyne.
The C. G. S. or fundamental unit of force. It is the force which can
impart an acceleration of one centimeter per second to a mass of one
gram in one second. It is equal to about 1/981 the weight of a gram,
this weight varying with the latitude.
Earth.
(a) The earth is arbitrarily taken as of zero electrostatic potential.
Surfaces in such condition that their potential is unchanged when
connected to the earth are said to be of zero potential. All other
surfaces are discharged when connected to the earth, whose potential,
for the purposes of man at least, never changes.
(b) As a magnetic field of force the intensity of the earth's field is
about one-half a line of force per square centimeter.
(c) The accidental grounding of a telegraph line is termed an earth, as
a dead, total, partial, or intermittent earth, describing the extent and
character of the trouble.
[Transcriber's note: Fallen power lines can produce voltage gradients on
the earth's surface that make walking in the area dangerous, as in
hundreds of volts per foot. Lightning may be associated with substantial
changes in the static ground potential.]
Earth, Dead.
A fault, when a telegraph or other conductor is fully connected to earth
or grounded at some intermediate point.
Synonyms--Solid Earth--Total Earth.
Earth, Partial.
A fault, when a telegraph or other conductor is imperfectly connected to
earth or grounded at some intermediate point.
Earth Plate.
A plate buried in the earth to receive the ends of telegraph lines or
other circuits to give a ground, q. v. A copper plate is often used. A
connection to a water or gas main gives an excellent ground, far better
than any plate. When the plate oxidizes it is apt to introduce
resistance.
Earth Return.
The grounding of a wire of a circuit at both ends gives the circuit an
earth return.
Earth, Swinging.
A fault, when a telegraph or other conductor makes intermittent
connection with the earth. It is generally attributable to wind action
swinging the wire, whence the name.
Ebonite.
Hard vulcanized India rubber, black in color. Specific resistance in
ohms per cubic centimeter at 46º C. (115º F.): 34E15 (Ayrton); specific
inductive capacity, (air = 1): 2.56 (Wüllner); 2.76 (Schiller); 3.15
(Boltzmann). It is used in electrical apparatus for supporting members
such as pillars, and is an excellent material for frictional generation
of potential. Its black color gives it its name, and is sometimes made a
point of distinction from Vulcanite, q. v.