The Standard Electrical Dictionary / A Popular Dictionary of Words and Terms Used in the Practice of Electrical Engineering

by T. O'Conor Sloane

Fig. 345. CARDEW VOLTMETER.
In this construction for a given expansion of the wire the piece c only
moves one half as much. The advantage of using a wire twice as long as
would be required for the same degree of movement were the full
expansion utilized is that a very thin wire can be employed. Such a wire
heats and cools more readily, and hence the instrument reaches its
reading more quickly or is more deadbeat, if we borrow a phraseology
properly applicable only to instruments with oscillating indexes.
In the most recent instruments about thirteen feet of wire .0025 inch in
diameter, and made of platinum-silver alloy is used.
571 STANDARD ELECTRICAL DICTIONARY.
If the potential difference to be measured lies between 30 and 120 volts
the wire as described suffices. But to extend the range of the
instrument a resistance in series is required. If such resistance is
double that of the instrument wire, and remains double whether the
latter is hot or cold the readings on the scale will correspond to
exactly twice the number of volts. This is brought about in some
instruments by the introduction in series of a duplicate wire, precisely
similar to the other wire, and like it, carried around pulleys and kept
stretched by a spring.
[Transcriber's note: If the series resistance is twice that of the
voltmeter, the indicated voltage will be ONE THIRD of the total
voltage.]
Thus whatever ratio of resistance exists between the two wires cold, it
is always the same at any temperature, as they both increase in
temperature at exactly the same rate. Tubes are provided to enclose the
stretched wires and pulleys, which tubes are blackened.
The voltmeter is unaffected by magnetic fields, and, as its
self-induction is very slight, it is much used for alternating currents.
The tubes containing the wire may be three feet long.
Its disadvantages are thus summarized by Ayrton. It absorbs a good deal
of energy; it cannot be constructed for small potential differences, as
the wire cannot be made thicker, as it would make it more sluggish;
there is vagueness in the readings near the zero point and sometimes
inaccuracy in the upper part of the scale.
Volts, Lost.
The volts at the terminals of a dynamo at full load fall short of their
value on open circuit. The difference of the two values are termed lost
volts.
Voltmeter, Electrostatic.
A voltmeter based on the lines of the quadrant electrometer. It includes
two sets of quadrants, each oppositely excited by one of the two parts,
whose potential difference is to be determined. They attract each other
against a controlling force as of gravity.
One form has the two sets poised on horizontal axes, bringing the parts
so that the flat quadrants move in vertical planes.
In another form a number of quadrants are used in each set, the members
of the two sets alternating with each other. One set is fixed, the
others move and carry the index.
Vulcanite.
Vulcanized india rubber which by high proportion of sulphur and proper
vulcanization has been made hard. It is sometimes distinguished from
ebonite as being comparatively light in color, often a dull red, while
ebonite is black. For its electrical properties see Ebonite.
Both substances have their defects, in producing surface leakage.
Washing with weak ammonia, or with dilute soda solution, followed by
distilled water, is recommended for the surface, if there is any trouble
with surface leakage. It may also be rubbed over with melted paraffine
wax.

572 STANDARD ELECTRICAL DICTIONARY.
W.
(a) A symbol or abbreviation for watt.
(b) A symbol or abbreviation for work.
(c) A symbol or abbreviation for weight.
Wall Bracket.
A telegraph bracket to be attached to the external walls of buildings to
which wires are attached as they come from the poles to reach
converters, or for direct introduction into a building.
Wall Sockets.
Sockets for incandescent lamps constructed to be attached to a wall.
Ward.
Direction in a straight line; a term proposed by Prof. James Thompson.
The words "backward" and "forward" indicate its scope.
Water.
A compound whose molecule consists of two atoms of hydrogen and one atom
of oxygen; formula, H2 O.
Its specific gravity is 1, it being the base of the system of specific
gravities of solids and liquids.
If pure, it is almost a non-conductor of electricity. If any impurity is
present it still presents an exceedingly high, almost immeasurable true
resistance, but becomes by the presence of any impurity an electrolyte.
Water Equivalent.
In a calorimeter of any kind the weight of water which would be raised
as much as is the calorimeter with its contents by the addition of any
given amount of heat received by the calorimeter.
Waterproof Lamp Globe.
An outer globe for incandescent lamps, to protect them from water.
Watt.
(a) The practical unit of electric activity, rate of work, or rate of
energy. It is the rate of energy or of work represented by a current of
one ampere urged by one volt electro-motive force; the volt-ampere.
It is the analogue in electricity of the horse power in mechanics;
approximately, 746 watts represent one electric horse power.
Ohm's law, taken as C = E/R, gives as values for current, C and E/R, and
for electro- motive force C R. In these formulas, C represents current
strength, R represents resistance and E represents electro-motive force.
Then a watt being the product of electro-motive force by current
strength, we get the following values for rate of electric energy, of
which the watt is the practical unit: (1) E2/R -- (2) C*E -- (3) C2 * R.
The equivalents of the watt vary a little according to different
authorities. Ayrton gives the following equivalents: 44.25 foot pounds
per minute--.7375 foot pounds per second--1/746 horse power. These
values are practically accurate. Hospitalier gives .7377 foot pounds per
second. Hering gives .737324 foot pounds per second, and 1000/745941
horse power.
573 STANDARD ELECTRICAL DICTIONARY.
It is equal to 1E7 ergs per second.
Synonym--Volt-ampere.
(c) It has been proposed to use the term as the unit of energy, instead
of activity or rate of energy (Sir C. W. Siemens, British Association,
1882); this use has not been adopted and may be regarded as abandoned.
[Transcriber's note; Watt is a unit of POWER--energy per unit of time.]
Watt-hour.
A unit of electric energy or work; one watt exerted or expended for one
hour.
It is equivalent to :
866.448 gram-degrees C. (calories)
2654.4 foot lbs.
3600 watt-seconds or volt-coulombs.
60 watt-minutes.
Watt-minute.
A unit of electric energy or work; one watt exerted or expended for one
minute.
It is equivalent to
14.4408 gram-degrees C. (calories),
44.240 foot pounds,
60 watt seconds or volt-coulombs,
1/60 watt hour.
Watts, Apparent.
The product in an alternating current dynamo of the virtual amperes by
the virtual volts. To give the true watts this product must be
multiplied by the cosine of the angle of lead or lag. (See Current,
Wattless.)
[Transcriber's note: This is now called a volt-amp. The usual usage is
KVA, or kilovolt-ampere.]
Watt-second.
A unit of electric energy or work. One watt exerted or expended for one
second.
It is equivalent to
.24068 gram degree C. (calorie),
.000955 lb. degree F.,
.737337 foot lbs.,
.0013406 horse power second (English),
.0013592 horse power second (metric).
Synonym--Volt-coulomb.
Waves, Electro-magnetic.
Ether waves caused by electromagnetic disturbances affecting the
luminiferous ether. (See Discharge, Oscillatory--Maxwell's Theory of
Light--Resonance. Electric.)
[Transcriber's note: The Michaelson-Morley experiment (1887) had already
called ether into question, but quantum theory and photons are decades
in the future.]
574 STANDARD ELECTRICAL DICTIONARY.
Weber.
(a.) A name suggested by Clausius and Siemens to denote a magnet pole of
unit strength. This use is abandoned.
(b.) It has been used to designate the unit of quantity--the coulomb.
This use is abandoned.
(c.) It has been used to designate the unit of current strength the
ampere. This use is abandoned.
[Transcriber's note: Definition (a) is now used. One weber of magnetic
flux linked to a circuit of one turn produces an electromotive force of
1 volt if it is reduced to zero at a uniform rate in 1 second.]
Weber-meter.
An ampere-meter or ammeter. The term is not used since the term "weber,"
indicating the ampere or coulomb, has been abandoned.
Welding, Electric.
Welding metals by heat produced by electricity. The heat may be produced
by a current passing through the point of junction (Elihu Thomson) or by
the voltaic arc. (Benardos & Olzewski.)

Fig. 346. ELECTRIC WELDING INDUCTION COIL.
The current process is carried out by pressing together the objects to
be united, while holding them in conducting clamps. A heavy current is
turned on by way of the clamps and rapidly heats the metals at the
junction, which is of course the point of highest resistance. As the
metal softens, it is pressed together, one of the clamps being mounted
with feed motion, flux is dropped on if necessary, and the metal pieces
unite.
The most remarkable results are thus attained; almost all common metals
can be welded, and different metals can be welded together. Tubes and
other shapes can also be united. In many cases the weld is the strongest
part.
575 STANDARD ELECTRICAL DICTIONARY.
The alternating current is employed. A special dynamo is sometimes used
to produce it. This dynamo has two windings on the armature. One is of
fine wire and is in series with the field magnets and excites them. The
other is of copper bars, and connects with the welding apparatus, giving
a current of high intensity but actuated by low potential.
Where the special dynamo is not used, an induction coil or transformer
is used. The primary includes a large number of convolutions of
relatively fine wire; the secondary may only be one turn of a large
copper bar.
The cut shows in diagram an electric welding coil. P is the primary coil
of a number of turns of wire; S S is the secondary, a single copper bar
bent into an almost complete circle. It terminates in clamps D D for
holding the bars to be welded. B C, B' C are the bars to be welded. They
are pressed together by the screw J. The large coil I of iron wire
surrounding the coils represents the iron core.
The real apparatus as at present constructed involves many
modifications. The diagram only illustrates the principle of the
apparatus.
In welding by the voltaic arc the place to be heated is made an
electrode of an arc by connection with one terminal of an electric
circuit. A carbon is connected to the other terminal. An arc is started
by touching and withdrawal of the carbon. The heat may be used for
welding, soldering, brazing, or even for perforating or dividing metal
sheets.
Welding Transformer.
The induction coil or transformer used in electric welding. For its
general principles of construction, see Welding, Electric.
Wheatstone's Bridge.
A system of connections applied to parallel circuits, including
resistance coils for the purpose of measuring an unknown resistance. A
single current is made to pass from A through two parallel connected
branches, joining together again at C. A cross connection B D has a
galvanometer or other current indicator in circuit. In any conductor
through which a current is passing, the fall of potential at given
points is proportional to the resistance between such points. Referring
to the diagram a given fall of potential exists between A and C. The
fall between A and B is to the fall between A and C as the resistance r
between A and B is to the resistance r + r' between A and C. The same
applies to the other branch, with the substitution of the resistances s
and S' and the point D for r r' and B. Therefore, if this proportion
holds, r : r' : : s : S'. No current will go through B D , and the
galvanometer will be unaffected. Assume s' to be of unknown resistance,
the above proportion will give it, if r, r' and s are known, or if the
ratio of r to r' and the absolute value of s is known.
576 STANDARD ELECTRICAL DICTIONARY.
In use the resistances r, r', and s are made to vary as desired. To
measure an unknown resistance it is introduced at S', and one of the
other resistances is varied until the galvanometer is unaffected. Then
the resistance of S' is determined by calculation as just explained. The
artificial resistances may be resistance coils, q. v., or it is enough
to have one unknown resistance at s. Then if the length of wire ABC is
accurately known, the point B can be shifted along it until the balance
is attained. The relative lengths A B, and B C, will then give the ratio
r : r' needed for the calculation. This assumes the wire ABC to be of
absolutely uniform resistance. This is the principle of the meter-bridge
described below. The use of coils is the more common method and is
carried out by special resistance boxes, with the connections arranged
to carry out the exact principle as explained. The principle of
construction and use of a resistance box of the Wheatstone bridge type,
as shown in the cut, is described under Box Bridge, q. v.

FIG. 347. WHEATSTONE BRIDGE CONNECTIONS.

FIG. 348. TOP OF BOX BRIDGE.
577 STANDARD ELECTRICAL DICTIONARY.
The next cut shows the sliding form of bridge called the meter bridge,
if the slide wire is a meter long or a half- or a quarter-meter bridge,
etc., according to the length of this wire. It is described under Meter
Bridge, q. v. Many refinements in construction and in proper proportion
of resistances for given work apply to these constructions.
Synonyms--Electric Balance--Resistance Bridge--Wheatstone's Balance.

Fig. 349. METER BRIDGE.
Whirl, Electric.
(a) A conductor carrying an electric current is surrounded by circular
lines of force, which are sometimes termed an electric whirl.
(b) The Electric Flyer. (See Flyer, Electric.)
Wimshurst Electric Machine.
An influence machine for producing high potential or static electricity.
Two circular discs of thin glass are mounted on perforated hubs or
bosses of wood or ebonite. Each hub has a groove turned upon it to
receive a cord. Each disc is shellacked. They are mounted on a
horizontal steel spindle so as to face and to be within one-eighth of an
inch of each other. On the outside of each disc sixteen or eighteen
sectors of tinfoil or thin metal are cemented.
578 STANDARD ELECTRICAL DICTIONARY.
Two curved brass rods terminating in wire brushes curved into a
semi-ellipse just graze the outer surfaces of the plates with their
brushes. They lie in imaginary planes, passing through the axis of the
spindle and at right angles from each other.
Four collecting combs are arranged horizontally on insulating supports
to collect electricity from the horizontal diameters of the discs. These
lie at an angle of about 45° with the other equalizing rods. Discharging
rods connect with the collecting combs.
The principle of the machine is that one set of sector plates act as
inductors for the other set. Its action is not perfectly understood.
It works well in damp weather, far surpassing other influence machines
in this respect. On turning the handle a constant succession or stream
of sparks is produced between the terminals of the discharging rods.
Windage.
In a dynamo the real air gap between the armature windings and pole
pieces is sometimes thus termed.
Wind, Electric.
The rush of air particles from a point connected to a statically charged
condenser.
Winding, Compound.
A method of winding a generator or motor in which a shunt winding is
used for the field magnets and in which also a second winding of the
magnet is placed in series with the outer circuit. (See Winding,
Series--Winding, Shunt.)