Fig. 191. COMPASS SUSPENDED IN GIMBALS.
Glass.
A fused mixture of silicates of various oxides. It is of extremely
varied composition and its electric constants vary greatly. Many
determinations of its specific resistance have been made. For flint
glass at 100° C. (212° F.) about (2.06E14) ohms --at 60° C (140° F.)
(1.020E15) (Thomas Gray) is given, while another observer (Beetz) gives
for glass at ordinary temperatures an immeasurably high resistance. It
is therefore a non-conductor of very high order if dry. As a dielectric
the specific inductive capacity of different samples of flint glass is
given as 6.57--6.85--7.4--10.1 (Hopkinson), thus exceeding all other
ordinary dielectrics. The densest glass, other things being equal, has
the highest specific inductive capacity.
Gold.
A metal, one of the elements; symbol Au. c .; atomic weight, 196.8;
equivalent, 65.6; valency, 3; specific gravity 19.5.
It is a conductor of electricity.
Annealed. Hard drawn.
Relative Resistance (Annealed Silver = 1), 1.369 1.393
Specific Resistance, 2.058 2.094
Resistance of a wire at 0° C. (32°F.)
(a) 1 foot long, weighing 1 grain, 57.85 58.84 ohms
(b) 1 foot long, 1/1000 inch thick, 12.38 12.60 "
(c) 1 meter long, weighing 1 gram, .4035 .4104 "
(d) 1 meter long, 1 millimeter thick, .02620 .02668 "
Resistance of a 1 inch cube at 0° C.(32° F.) .8102 .8247
Approximate increase in resistance per 0° C., (1.8° F)
at about 20° C. (68° F.), 0.365 per cent.
Electro-chemical equivalent (Hydrogen = .0105), .6888
279 STANDARD ELECTRICAL DICTIONARY.
Gold Bath.
A solution of gold used for depositing the metal in the electroplating
process.
A great number of formulae have been devised, of which a few
representative ones are given here.
COLD BATHS. HOT BATHS.
Water, 10,000 10,000 10,000 10,000 5,000 3,000
Potassium Cyanide, 200 -- 200 10 -- 50
Gold, 100 15 100 10 10 10
Potassium Ferrocyanide, -- 200 -- -- 150 --
Potassium Carbonate, -- 150 -- -- 50 --
Ammonium Chloride, -- 30 -- -- 20 --
Aqua Ammoniae, -- -- 500 -- -- --
Sodium Phosphate, -- -- -- 600 -- --
Sodium Bisulphite, -- -- -- 100 -- --
(Roseleur.)
In the baths the gold is added in the form of neutral chloride, Auric
chloride (Au Cl6).
Gold Stripping Bath.
A bath for removing gold from plated articles without dissolving the
base in order to save the precious metal. A bath of 10 parts of
potassium cyanide and 100 parts of water may be used, the articles to be
stripped being immersed therein as the anode of an active circuit. If
the gilding is on a silver or copper basis, or on an alloy of these
metals the same solution attacks the base and dissolves it, which is
objectionable. For silver articles it is enough to heat to cherry red
and throw into dilute sulphuric acid. The gold scales off in metallic
spangles. For copper articles, a mixture of 10 volumes concentrated
sulphuric acid, 1 volume nitric acid, and 2 volumes hydrochloric acid
may be used by immersion only, or with a battery. The sulphuric acid in
such large excess is supposed to protect the copper. For copper articles
concentrated sulphuric acid alone with the battery may be used. This
does not sensibly attack the copper if it is not allowed to become
diluted. Even the dampness of the air may act to dilute it.
Graduator.
Apparatus for enabling the same line to be used for telegraph signals
and telephoning.
One type consists in coils with iron cores or simply electromagnets.
These act to retard the current in reaching its full power and also
prolong it. This gives a graduated effect to the signals, so that the
telephone diaphragm is not audibly affected by the impulses.
The telephoning current is so slight and so rapid in its characteristic
changes that it is without effect upon the ordinary telegraph.
280 STANDARD ELECTRICAL DICTIONARY.
Gram.
The unit of weight in the metric system; accepted as the unit of
mass in the absolute of C. G. S. system of units. It is the
one-thousandth part of mass of a standard weight preserved under proper
conditions in Paris, and supposed to be the mass of a cubic decimeter of
distilled water at the temperature of the maximum density of water. The
standard is the kilogram; the temperature is 3.9º C. (39º F.). The
standard kilogram is found to be not exactly the weight of a cubic
decimeter of water, the latter weighing 1.000013 kilogram.
If therefore the defined gram on the water basis is taken as the unit it
varies very slightly from the accepted gram.
1 gram is equal to 15.43234874 grains. (Prof. W. H. Miller.)
Gram-atom.
The number of grams of an element equal numerically to the atomic
weight, as 16 grams of oxygen, 1 gram of hydrogen, 35.5 grams of
chlorine; all which might be expressed as gram-atoms of oxygen, hydrogen
and chlorine respectively.
The gram-atom approximately expresses the number of gram-calories
required to heat one gram of the substance 1º C. (1.8º F.). This is in
virtue of Dulong and Petit's discovery that the atomic weight of an
element multiplied by its specific heat gives approximately a constant
for all elements.
[Transcriber's note: A gram-atom is the mass, in grams, of one mole of
atoms in a monatomic element. A mole consists of Avogadro's number of
atoms, approximately 6.02214E23.]
Gram-molecule.
The number of grams of a substance equal numerically to its molecular
weight.
Graphite.
Carbon; one of three allotropic modifications of this element. It occurs
in nature as a mineral.
It is used as a lubricant for machinery; for commutator brushes; for
making surfaces to be plated conductive, and for mixing with manganese
binoxide in Leclanché cells.
Gravitation.
A natural force which causes all masses of matter to attract each other.
Its cause is unknown; it is often supposed to be due to the luminiferous
ether.
[Transcriber's note: Einstein's explanation of gravity, General
Relativity and the curvature of space-time, came 23 years later, 1915.]
281 STANDARD ELECTRICAL DICTIONARY.
Gravity, Acceleration of.
The velocity imparted to a body in one second by the action of
gravitation at any standard point upon the earth's surface in a vacuum.
This will vary at different places, owing principally to the variation
in centrifugal force due to the earth's rotation. For standard valuation
it must be reduced to sea level. The following are examples of its
variation:
Equator, 978.1028 centimeters per second
Paris, 980.94 "
Greenwich 981.I7 "
Edinburgh, 981.54 "
Pole (N. or S.), 983.1084 (theoretical) "
As round numbers for approximate calculations 981 centimeters or 32.2
feet may be employed.
[Transcriber's note: The acceleration of gravity at the equator is also
reduced by the increased distance from the center of the earth
(equatorial bulge). Increased altitude reduces gravity. Reduced air
density at altitude reduces buoyancy and increases apparent weight.
Local variations of rock density affects gravity.]
Gravity, Control.
Control by weight. In some ammeters and voltmeters gravity is the
controlling force.
Grid.
A lead plate perforated or ridged for use in a storage battery as the
supporter of the active materials and in part as contributing thereto
from its own substance.
Ground.
The contact of a conductor of an electric circuit with the earth,
permitting the escape of current if another ground exists.
Ground-wire.
A metaphorical term applied to the earth when used as a return circuit.
Fig. 192. GROVE'S GAS BATTERY.
Grove's Gas Battery.
A voltaic battery depending for its action on the oxidation of hydrogen
instead of the oxidation of zinc. Its action is more particularly
described under Battery, Gas. In the cut B, B1 * * * are the terminals
of the positive or hydrogen electrodes, marked H, and A, Al * * * are
the terminals of the negative or oxygen electrodes marked O, while M, M1
* * * is dilute sulphuric acid.
282 STANDARD ELECTRICAL DICTIONARY.
Guard Ring.
An annular horizontal surface surrounding the balanced disc in the
absolute electrometer. (See Electrometer, Absolute.)
Guard Tube.
A metal tube surrounding a dry pile used with a quadrant electrometer,
or other electrometers of that type. It prevents the capacity of the
lower brass end of the pile (which brass end closes the glass tube
containing the discs) from momentary change by approach of some
conductor connected to the earth. There are other guard tubes also.
Gun, Electro-magnetic.
An electro-magnet with tubular core. If, when it is excited a piece of
an iron rod is pushed into the central aperture of the core and is
released, the magnetic circle will try to complete itself by pushing the
rod out so that it can thus be discharged, as if from a popgun.
Synonym--Electric Popgun.
Fig. 193. "ELECTRIC POPGUN."
Gutta Percha.
The hardened milky juice of a tree, the Isonandra gutta, growing in
Malacca and other parts of the Eastern Archipelago. It is much used as
an insulator or constituent of insulators.
Resistance after several minutes electrification per 1 centimeter cube
at 54º C. (75º F.), 4.50E14 ohms.
The specific resistance varies--from 2.5E13 to 5.0E14 ohms. A usual
specification is 2.0E14 ohms. The influence of temperature on its
resistance is given in Clark & Bright's empirical formula, R = R0 at, in
which R is the resistance at temperature tº C--Ro the resistance at 0º C
(32º F), a is the coefficient .8944.
The resistance increases with the time of passage of the current, the
variation being less the higher the temperature.
283 STANDARD ELECTRICAL DICTIONARY.
Time of Relative Resistance Relative Resistance
Electrification. at 0º C (32º F.) at 24º C (75º F.)
1 minute 100 5.51
2 " 127.9 6.
5 " 163.1 6.66
10 " 190.9 6.94
20 " 230.8 7.38
30 " 250.6 7.44
60 " 290.4 7.6
90 " 318.3 7.66
In cable testing one minute is generally taken as the time of
electrification.
Pressure increases the resistance by the formula Rp=R (1+ .00327 P) in
which Rp is the resistance at pressure p--R resistance at atmospheric
pressure--p pressure in atmospheres. Thus in the ocean at a depth of
4,000 meters (2.4855 miles), the resistance is more than doubled. The
longer the pressure is applied, the greater is the resistance.
The specific inductive capacity of gutta percha is 4.2.
Good gutta percha should not break when struck with a hammer, should
recover its shape slowly, and it should support much more than 300 times
its own weight.
Gyrostatic Action of Armatures.
Owing to gyrostatic action a rotating armature resists any change of
direction of its axis. On ships and in railway motors which have to turn
curves this action occurs. A 148 lb. armature running at 1,300
revolutions per minute may press with 30 lbs. on each journal as the
ship rolls through an angle of 20° in 16 seconds.
283 STANDARD ELECTRICAL DICTIONARY.
H.
(a) The symbol for the horizontal component of the earth's
magnetization.
(b) The symbol for the intensity of a magnetizing force or field. The
symbol H, as it is generally used, may mean either the number of dynes
which act upon a unit pole, or the number of lines of force per
centimeter.
(c) The symbol for the unit of self-induction.
Hair, Removal of, by Electrolysis.
A method of depilation by destruction of individual hair follicles by
electrolysis.
A fine platinum electrode is thrust into a hair follicle. It is the
negative electrode. The positive electrode is in contact with the body
of the person under treatment; it is often a sponge electrode simply
held in his hand. A current of two to four milliamperes from an E. M. F.
of 15 to 20 volts, is passed. This destroys the follicle, the hair is
removed and never grows again. A gradual increase of current is advised
for the face. As only one hair is removed at once, but a small number
are taken out at a sitting.
284 STANDARD ELECTRICAL DICTIONARY.
Haldat's Figures.
With a pole of a strong bar magnet, used like a pencil, imaginary
figures are drawn upon a hard steel plate, such as a saw-blade. The
pattern is gone over several times. By dusting iron filings on a sheet
of paper laid over the steel plate, while horizontal, very complicated
magnetic figures are produced.
Hall's Experiment.
A cross of thin metal, such as gold leaf, is secured upon a pane of
glass. To two opposite arms a battery is connected in circuit with them.
To the other two arms a galvanometer is connected in circuit. If the
cross is put into a field of force whose lines are perpendicular
thereto, the galvanometer will disclose a constant current. The current
is pushed, as it were, into the galvanometer circuit. Other metals have
been used with similar results. They must be thin or the experiment
fails. If the arm receiving the battery current is horizontal, and if it
flows from left to right, and if the lines of force go from downward
through the cross, the current in the galvanometer circuit will flow
from the observer through the other arms of the cross, if the cross is
of gold, silver, platinum or tin, and the reverse if of iron. The
experiment has indicated a possible way of reaching the velocity of
electricity in absolute measure.
Hall Effect.
The effect observed in Hall's experiment, q. v.
Hall Effect, Real.
A transverse electro-motive force in a conductor through which a current
is passing produced by a magnetic field.
Hall Effect, Spurious.
A spurious electro-motive force produced in a conductor, through which a
current is passing by changes in conductivity of the conductor brought
about by a magnetic field.
Hanger Board.
A board containing two terminals, a suspending hook, and a switch, so
that an arc lamp can be introduced into a circuit thereby, or can be
removed as desired.
Harmonic Receiver.
A receiver containing a vibrating reed, acted on by an electro-magnet.
Such a reed answers only to impulses tuned to its own pitch. If such are
received from the magnet it will vibrate. Impulses not in tune with it
will not affect it. (See Telegraph, Harmonic.)
Head Bath, Electric.
A fanciful name for an electro-medical treatment of the head. The
patient is insulated by an insulating stool or otherwise. His person is
connected with one terminal of an influence machine. An insulated
metallic circle, with points of metal projecting inward or downward, is
placed about the head. The circle is connected with the other pole of
the machine. On working it a silent or brush discharge with air
convection streams occurs between the patient's head and the circle of
points.
285 STANDARD ELECTRICAL DICTIONARY.
Head-light, Electric.
An electric head-light for locomotives has been experimented with. It
includes the parabolic reflection of the regular light with an arc-lamp
in place of the oil lamp. An incandescent lamp may be used in the same
place, but has no great advantage over oil as regards illuminating
power.
Heat.
A form of kinetic energy, due to a confused oscillatory movement of the
molecules of a body. Heat is not motion, as a heated body does not
change its place; it is not momentum, but it is the energy of motion. If
the quantity of molecular motion is doubled the momentum of the
molecules is also doubled, but the molecular mechanical energy or heat
is quadrupled.
As a form of energy it is measured by thermal units. The calorie is the
most important, and unfortunately the same term applies to two units,
the gram-degree C. and the kilogram-degree C. (See Calorie.) Calories
are determined by a calorimeter, q. v.
Independent of quantity of heat a body may be hotter or colder.
Thermometers are used to determine its temperature.
Heat is transmitted by conduction, a body conducting it slowly for some
distance through its own substance. Bodies vary greatly in their
conductivity for heat. It is also transmitted by convection of gases or
liquids, when the heated molecules traveling through the mass impart
their heat to other parts. Finally it is transmitted by ether waves with
probably the speed of light. This mode of transmission and the phenomena
of it were attributed to radiant heat. As a scientific term this is now
dropped by many scientists. This practice very properly restricts the
term "heat" to kinetic molecular motion.
The mechanical equivalent of heat is the number of units of work which
the energy of one unit quantity of heat represents. (See Equivalents,
Mechanical and Physical.)
Heat, Atomic.
The product of the specific heat of an element by its atomic weight. The
product is approximately the same for all the elements, and varies as
determined between 5.39 and 6.87. The variations are by some attributed
principally to imperfection of the work in determining them. The atomic
heat represents the number of gram calories required to raise the
temperature of a gram atom (a number of grams equal numerically to the
atomic weight) one degree centigrade.
286 STANDARD ELECTRICAL DICTIONARY.
Heat, Electric.
This term has been given to the heat produced by the passage of a
current of electricity through a conductor. It is really electrically
produced heat, the above term being a misnomer.
The rise of temperature produced in a cylindrical conductor by a current
depends upon the diameter of the conductor and on the current. The
length of the wire has only the indirect connection that the current
will depend upon the resistance and consequently upon its length.
The quantity of heat produced in a conductor by a current is in
gram-degree C. units equal to the product of the current, by the
electro-motive force or potential difference maintained between the ends
of the wire, by .24.
The cube of the diameter of a wire for a given rise of temperature
produced in such conductor by a current is equal approximately to the
product of the square of the current, by the specific resistance (q. v.)
of the material of the conductor, by .000391, the whole divided by the
desired temperature in centigrade units.
Heat, Electrical Convection of.
A term applied to the phenomena included under the Thomson effect, q.
v., the unequal or differential heating effect produced by a current of
electricity in conductors whose different parts are maintained at
different temperatures.
Heater, Electric.
An apparatus for converting electrical energy into thermal energy.
An incandescent lamp represents the principle, and in the Edison meter
has been used as such to maintain the temperature of the solutions.
Heaters for warming water and other purposes have been constructed,
utilizing conductors heated by the passage of the current as a source of
heat. (See also Heating Magnet.)
Heating Error.
In voltmeters the error due to alteration of resistance of the coil by
heating. If too strong a current is sent through the instrument, the
coils become heated and their resistance increased. They then do not
pass as much current as they should for the potential difference to
which they may be exposed. Their readings then will be too low. One way
of avoiding the trouble is to have a key in circuit, and to pass only an
instantaneous or very brief current through the instrument and thus get
the reading before the coils have time to heat.
The heating error does not exist for ammeters, as they are constructed
to receive the entire current, and any heating "error" within their
range is allowed for in the dividing of the scale.
Heating Magnet.
An electro-magnet designed to be heated by Foucault currents induced in
its core by varying currents in the windings. It has been proposed as a
source of artificial heat, a species of electric heating apparatus for
warming water, or other purposes.
287 STANDARD ELECTRICAL DICTIONARY.
Heat, Irreversible.
The heat produced by an electric current in a conductor of identical
qualities and temperature throughout. Such heat is the same whatever the
direction of the current. The heating effect is irreversible because of
the absence of the Thomson effect, q. v.) or Peltier effect, q. v.
Heat, Mechanical Equivalent of.
The mechanical energy corresponding to a given quantity of heat energy.
Mechanical energy is generally represented by some unit of weight and
height, such as the foot-pound; and heat energy is represented by a
given weight of water heated a given amount, such as a pound-degree
centigrade. Joule's equivalent is usually accepted; it states that
772.55 foot pounds of mechanical energy are equivalent to 1 pound-degree
F. (one pound avds. of water raised in temperature one degree
Fahrenheit). Other equivalencies have also been deduced.
Heat, Molecular.
The product of a specific heat of the compound by its molecular weight.
It is approximately equal to the sum of the atomic heats of its
constituent elements.
The molecular heat represents the number of gram calories required to
raise the temperature of a gram-molecule (a number of grams equal
numerically to the molecular weight) one degree centigrade.
The molecular heat is approximately equal for all substances.
Heat, Specific.
The capacity of a body for heat; a coefficient representing the relative
quantity of heat required to raise the temperature of an identical
weight of a given body a defined and identical amount.
The standard of comparison is water; its specific heat is taken as
unity. The specific heats by weight of other substances are less than
unity. The specific heat varies with the temperature. Thus the specific
heat of water is more strictly 1+.00015 tº C.
Specific heat is greater when a substance is in the liquid than when it
is in the solid state. Thus the specific heat of ice is 0.489; less
than half that of water. It differs with the allotropic modifications of
bodies; the specific heat of graphite is .202; of diamond, .147.
The product of the specific heat by the atomic weight of elements gives
a figure approximately the same. A similar law applies in the case of
molecules. (See Heat, Atomic-Heat, Molecular.)
The true specific heat of a substance should be separated from the heat
expended in expanding a body against molecular and atomic forces, and
against the atmospheric pressure. So far this separation has not been
possible to introduce in any calculations.
288 STANDARD ELECTRICAL DICTIONARY.
Heat, Specific, of Electricity.
A proposed term to account for the heat absorbed or given out in
unhomogeneous conductors, by the Thomson effect, or Peltier effect (see
Effect, Thomson--Effect, Peltier.) If a current of electricity be
assumed to exist, then under the action of these effects it may be
regarded as absorbing or giving out so many coulombs of heat, and thus
establishing a basis for specific heat.
Heat Units.
The British unit of heat is the pound degree F--the quantity of heat
required to raise the temperature of a pound of water from 32° to 33° F.
The C. G. S. unit is the gram-degree C.; another metric unit is the
kilogram-degree C. The latter is the calorie; the former is sometimes
called the small calorie or the joule; the latter is sometimes called
the large calorie. The term joule is also applied to a quantity of heat
equivalent to the energy of a watt-second or volt-coulomb. This is equal
to .24l gram degree calorie.
Hecto.
A prefix to terms of measurement--meaning one hundred times, as
hectometer, one hundred meters.
Heliograph.
An apparatus for reflecting flashes of light to a distant observer. By
using the Morse telegraph code messages may thus be transmitted long
distances. When possible the sun's light is used.
Helix.
A coil of wire; properly a coil wound so as to follow the outlines of a
screw without overlaying itself.
Fig. 194. LEFT-HANDED HELIX.
Fig. 195. RIGHT-HANDED HELIX.
Henry.
The practical unit of electro-magnetic or magnetic inductance. It is
equal to 1E9 C. G. S., or absolute units of inductance. As the
dimensions of inductance are a length the henry is equal to 1E9
centimeters, or approximately to one quadrant of the earth measured on
the meridian.
Synonyms--Secohm--Quadrant--Quad.
289 STANDARD ELECTRICAL DICTIONARY.
Hermetically Sealed.
Closed absolutely tight. Glass vessels, such as the bulbs of
incandescent lamps, are hermetically sealed often by melting the glass
together over any opening into their interior.
Heterostatic Method.
A method of using the absolute or attracted disc electrometer. (See
Electrometer Absolute.) The formula for its idiostatic use, q. v.,
involves the determination of d, the distance between the suspended and
fixed discs. As this is difficult to determine the suspended disc and
guard ring may be kept at one potential and the lower fixed disc is then
connected successively with the two points whose potential difference is
to be determined. Their difference is determined by the difference
between d and d', the two distances between the discs. This difference
is the distance through which the micrometer screw is moved. The
heterostatic formula is:
V' - V = (d' - d)* squareRoot( 8*PI*F / S )
in which V and V' are potentials of the two points; d' and d the two
distances between the discs necessary for equilibrium; S the area of the
disc and F the force of attraction in dynes. (See Idiostatic Method.)
High Bars of Commutator.
Commutator bars, which in the natural wear of the commutator, project
beyond the others. The surface then requires turning down, as it should
be quite cylindrical.
High Frequency.
A term used as a noun or as an adjective to indicate in an alternating
current, the production of a very great number of alternations per unit
of time--usually expressed as alternations per second.
Hissing.
A term applied to a noise sometimes produced by a voltaic arc; probably
due to the same cause as frying, q. v.
Hittorf's Solution.
A solution used as a resistance. It is a solution of cadmium iodide in
amylic alcohol. Ten per cent. of the salt is used. It is contained in a
tube with metallic cadmium electrodes. (See Resistance, Hittorf' s.)
Fig. 196. HITTORF'S RESISTANCE TUBE.
290 STANDARD ELECTRICAL DICTIONARY.
Holders.
(a) The adjustable clamps for holding the armature brushes of dynamos
and motors.
(b) The clamps for holding the carbons of arc lamps.
(c) The clamps for holding safety fuses, q. v.
(d) Holders for Jablochkoff candles and other electric candles. (See
Candle Holders.)
(e) A box or block of porcelain for holding safety fuses.
Hood.
A tin hood placed over an arc-lamp. Such hoods are often truncated cones
in shape, with the small end upwards. They reflect a certain amount of
light besides protecting the lamp to some extent from rain.
Horns.
The extensions of the pole pieces of a dynamo or motor. (See Following
Horns-Leading Horns.)
Synonym--Pole Tips.
Horse Power.
A unit of rate of work or activity. There are two horse powers.
The British horse power is equal to 33,000 pounds raised one foot per
minute, or 550 foot pounds per second, or 1.0138 metric horse power.
The metric horse power (French) is equal to 75 kilogram-meters, or 542
foot pounds per second, or .986356 British horse power.
H. P. is the abbreviation for horse power. (See Horse Power, Electric.)
Horse Power, Actual.
The rate of activity of a machine, as actually developed in condition
for use. It is less than the indicated or total horse power, because
diminished by the hurtful resistances of friction, and other sources of
waste. It is the horse power that can be used in practise, and which in
the case of a motor can be taken from the fly-wheel.
Horse Power, Electric.
The equivalent of a mechanical horse power in electric units, generally
in volt-amperes or watts; 745.943 watts are equivalent to the activity
of one British horse power; 735.75 are equivalent to one metric horse
power. The number 746 is usually taken in practical calculations to give
the equivalency.
[Transcriber's note: Contemporary values are: Mechanical (British)
horsepower = 745.6999 Watts; Metric horsepower = 735.49875 Watts]
Horse Power, Indicated.
The horse power of an engine as indicated by its steam pressure, length
of stroke, and piston area, and vacuum, without making any deduction for
friction or hurtful resistances. The steam pressure is in accurate work
deduced from indicator diagrams.
Horse Power, Hour.
A horse power exerted for one hour, or the equivalent thereof. As the
horse power is a unit of activity, the horse power hour is a unit of
work or of energy. It is equal to 1,980,000 foot pounds.
H. P.
Abbreviation for "horse power."
291 STANDARD ELECTRICAL DICTIONARY.
Hughes' Electro-magnet.
A horseshoe electro-magnet with polarized core. It is made by mounting
two bobbins of insulated wire on the ends of a permanent horseshoe
magnet. It was devised for use in Hughes' printing telegraph, where very
quick action is required. The contact lasts only .053 second, 185
letters being transmitted per minute.