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

by T. O'Conor Sloane

389 STANDARD ELECTRICAL DICTIONARY.
N.
(a) Symbol for north pole or north-seeking pole of a magnet.
(b) Symbol for the number of lines of force in a magnetic circuit.
Nairne's Electrical Machine.
The cylinder electrical machine, q.v.
Napierian Logarithms.
A series of logarithms the base of whose system is 2.72818. They are
also called hyperbolic logarithms.
Nascent State.
An element just separating from a combination possesses at that time
higher affinities than after separation, and can effect more powerful
chemical changes.
It is sometimes attributed to a differential time of existence in the
atomic modification, before the freed atoms have united to form
molecules.
Natural Currents.
A term for earth currents. (See Current, Earth.)
Needle.
(a) A term applied to a bar magnet poised horizontally upon a vertical
point, or suspended in a horizontal position by a filament. Thus the
magnet in a mariner's compass, which may be a substantial bar magnet, is
called a magnetic needle.
(b) An indicator in general shape like the hand of a clock. (Sec
Annunciator, Needle- Telegraph, Needle.)
Needle of Oscillation.
The magnetic needle poised horizontally, and used for measuring the
intensity of the earth's magnetic field, or of an artificial magnetic
field, by the method of oscillations. The intensities of the field is
inversely as the square of the number of oscillations performed in a
given time.
Needle, Telegraphic.
The index in needle telegraphy (see Telegraph, Needle), whose motions
indicate the characters it is desired to transmit.
Negative Charge.
One of the two kinds of electric charges. The other is the positive.
By the double fluid hypothesis this is assumed to be a charge of a
particular kind of electricity--negative electricity.
By the single fluid hypothesis it is supposed to be caused by the
absence of part of the normal electricity of a surface. The reverse is
held by some theorists.
The subject is so purely theoretical that neither of the two hypotheses
is accepted as final.
[Transcriber's note: Current is a wire is the motion of negative
electrons. Current in a electrolyte is the motion of positive ions and
negative ions. Current in a plasma is the motion of electrons and
positive ions.]
390 STANDARD ELECTRICAL DICTIONARY.
Negative Electricity.
The kind of electricity with which a piece of amber is charged by
friction with flannel; resinous electricity. (See Electrostatic Series.)
In a galvanic battery the surface of the zinc plate is charged with
negative electricity.
According to the single fluid theory negative electrification consists
in a deficiency of electricity.
[Transcriber's note: Negative electrification is an excess of
electrons.]
Negative Element.
In a voltaic cell the plate not dissolved by the solution; the one which
is positively charged; the copper, platinum, or carbon plate in the
usual type of battery.
The current is assumed to flow from negative element to positive element
(the zinc plate) through the wire or other external conductor.
Nerve Currents.
Currents of electricity obtained from nerves. They are much more feeble
than those obtained from muscle, but are produced in the same general
ways.
Network.
Conductors in parallel and crossing each other, with connections at the
junctions.
The term is sometimes so loosely applied as to include parallel
conductors.
Neutral Line of Commutator.
The diameter of a commutator which connects its Neutral Points, q. v.;
sometimes termed the diameter of commutation; the diameter approximately
at right angles with the lines of force. The commutator brushes are
applied at the extremities of this diameter.
Neutral Point of a Commutator.
The points of a commutator at which no lines of force are cut; the
points at the extremities of a diameter which, except for the lag, would
be at right angles to the lines of force; the points at which the
brushes touch the commutator.
Neutral Point, Thermo-electric.
A temperature marking a point of no thermo-electric difference of
potential. If the junctions of a thermo-electric couple are at
temperatures, one a little over and the other an equal amount under the
neutral point, no current will be developed. At the neutral point the
thermo-electric polarities are reversed. Differences of temperature
above it give currents of reverse direction to those given by
corresponding differences below it. For an iron-copper couple the
neutral point is 274.5° C. (526° F.)
Synonym--Neutral Temperature.
Neutral Relay Armature.
An unpolarizable armature for use with a relay; an armature of soft iron
or iron wire; as distinguished from a polarized armature.
391 STANDARD ELECTRICAL DICTIONARY.
Neutral Wire.
The central wire in the three wire system, q. v., of electric
distribution; the wire connected to a point between the two dynamos, or
otherwise to the central point of the current generator.

Fig. 250. DIAGRAM OF THREE WIRE SYSTEM SHOWING NEUTRAL WIRE.
Neutral Wire Ampere Meter.
An ampere meter connected in the circuit of the neutral wire to
determine the current passing through it. Such determination is for the
purpose of ascertaining how much more work is being done by one of the
lateral leads than by the other.
Synonym--Balance Ampere Meter.
N. H. P.
Symbol or contraction for "nominal horse power." This is a basis for
rating the size of an engine.
Nickel.
A metal; one of the elements; atomic weight, 58.8 ; equivalent, 29.4;
valency, 2; specific gravity, 8.8. It is a conductor of electricity.
Relative resistance, annealed (Silver = 1), 8.285
Specific Resistance, 12.47 microhms.
Resistance of a wire
(a) 1 foot long, weighing 1 grain, 15.206 ohms.
(b) 1 foot long, 1/1000 inch thick, 74.963 "
(c) 1 meter long, weighing 1 gram, 1.060 "
(d) 1 meter long, 1 millimeter thick, .1587 "
Resistance of a 1-inch cube, 4.907 microhms.
Electro-chemical equivalent, (Hydrogen = .0105) .3087 mgs.
It is strongly paramagnetic, but loses this quality at 350º C. (662º F.)
It is important as a constituent of German silver, an alloy much used
for resistance coils.
Nickel, Bath.
A bath for the electro-deposition of nickel. A great many
formulae have been given. Metallic nickel is dissolved in 1 vol.
sulphuric acid mixed with 2 vols. water. Neutralize with ammonia, and
add of ammonium sulphate one-half the weight of metallic nickel
originally used; 135 parts of nickel will be enough for a bath of 10,000
parts.
392 STANDARD ELECTRICAL DICTIONARY.
Other formulae are as follows:
Double nickel-ammonium sulphate, 4 parts.
Ammonium carbonate, 3 "
Water 100 "
Nickel sulphate, nitrate or chloride, 1 "
Sodium bisulphate, 1 "
Water, 20 "
Nickel anodes are used in the bath to maintain the strength. Too much
care cannot be exercised in the absolute cleanliness of the articles to
be plated. A too alkaline bath gives a disagreeable yellow color to the
deposit; too acid a bath gives badly adhering deposits.
Night Bell.
An alarm bell in a telegraph office, which bell is connected at night to
give a loud signal to attract the operator's attention. It is used in
telephone exchanges and is connected so as to ring as long as a
subscriber remains unanswered after calling.
Nobili's Rings.
When a dilute solution of copper acetate is placed on a bright silver
plate and a strip of zinc is touched to the silver beneath the copper, a
series of rings of copper are formed by electrolysis around the zinc.
These are Nobili's rings.
If for the copper acetate a solution of lead oxide in potassium hydrate
solution is substituted, and if the polished plate which may be German
silver is connected to the positive electrode of a battery, and a
platinum wire connected to the negative pole is immersed in the liquid,
it determines the formation of beautiful iridescent rings of lead
binoxide. The platinum wire is sometimes sealed in glass so that only
its point projects.
The colors are due to interference of light, the layers of lead oxide
being extremely thin.
The lead binoxide is formed by secondary reaction. Metallic lead is
first deposited on the negative pole. The oxygen which goes to the
positive pole formed by the polished plate produces lead binoxide which
is deposited there in rings. The reaction is comparable to that of a
storage battery.
Synonyms--Metallochromes--Electric Rings.
Nodular Deposit.
A deposit obtained in electroplating, characterized by irregular
thickness; due to too low density of current.
Non-conductor.
A material that does not conduct electricity except with great
difficulty; a substance of very high resistance.
Synonym--Insulator--Dielectric.
North Pole.
(a) The north-seeking pole of a magnet; the pole of a magnet which tends
to point to the north, and whence lines of force are assumed to issue on
their course to the other pole of the magnet.
(b) The North Pole of the earth. Treating the earth as a magnet, and
accepting the above nomenclature the north pole should be termed the
south pole. (See Austral Pole--Boreal Pole.)
393 STANDARD ELECTRICAL DICTIONARY.
North-seeking Pole.
The pole of a magnet which tends to point to the north; the north pole
of a magnet.
Null Method.
Any method of obtaining measurements or comparisons, in which the
measurement is correct when the deflection of the galvanometer or other
indicator is zero, nought or null. The Wheatstone Bridge (see Bridge,
Wheatstone) is an example of a null method.
Two obvious advantages attach to null methods in electric galvanometer
work. One is that an uncalibrated galvanometer can be employed. The
other is that a galvanometer of any high degree of sensitiveness can be
employed, there being no restriction as to its fineness of winding or
highness of resistance.

393 STANDARD ELECTRICAL DICTIONARY.

"Upper case Omega Graphic".
(Greek capital" Omega") symbol for megohm.
[Transcriber's note: Now used for ohms.]
"Lower case Omega Graphic".
(Greek omega) symbol for ohm.
[Transcriber's note: Now used for angular velocity, 2*PI*frequency.]
Occlusion.
An absorption of gases by metals. Palladium will, if used as the
hydrogen evolving electrode in decomposing water, absorb 980 times its
volume of hydrogen, which is said to be occluded. The metal may also be
heated in hydrogen and allowed to cool therein, when occlusion occurs.
Platinum will occlude 4 times its volume of hydrogen; iron, 4.15 times
its volume of carbon-monoxide; silver, 7 times its volume of oxygen.
Metals with occluded gases may serve as elements in a galvanic couple.
(See Gas Battery.) A metal expands in occluding a gas.
In the storage battery it is believed that occlusion plays a part,
hydrogen and oxygen being respectively absorbed by the two sets of
plates, and acting as they do in Groves' gas battery.
Oerstedt.
Name proposed for the unit of current strength, but not adopted. The
ampere is the accepted name.
394 STANDARD ELECTRICAL DICTIONARY.
Oerstedt's Discovery.
Oerstedt discovered in 1820 that a magnetic needle tended to place
itself at right angles to a current of electricity. This fundamental
experiment is the basis of the galvanometer.

Fig. 251. OERSTEDT'S DISCOVERY.
Ohm.
The practical unit of resistance; 1E9 C. G. S. electro-magnetic units.
The legal ohm is the resistance of a mercury column 1 square millimeter
in cross-sectional area and 106 centimeters in length. There has been
considerable confusion, owing to inaccuracy in early determinations, in
the valuation of the ohm. In this work the legal ohm is used. The
different ohms will be found defined in their place. Resistance units of
various names may also be consulted.
The following table gives the relative values of the different ohms.
Length of
Mercury Board of
Column in True B. A. Trade Legal
Centimetre. Ohm. Ohm. Ohm. Ohm.
True Ohm, 106.24 1. 1.0128 .9994 1.0022
B. A. Ohm, 104.9 .9874 1. .9868 .9889
Board of Trade Ohm 106.3 1.00050 1.0133 1. 1.0028
Legal Ohm, 106.0 .9977 1.0112 .9971 1.
Ohmage.
The Resistance of a circuit expressed in ohms.
Ohm, B. A.
The British Association unit of resistance; the resistance of a column
of mercury 1 square millimeter in cross sectional area and 104.9
centimeters long; the B. A. Unit of Resistance.
Ohm, Board of Trade.
The approximate ohm as recommended by the British Board of Trade on the
advice of a committee (Sir W. Thomson, Dr. J. Hopkinson, Lord Rayleigh
and others). It is the resistance of a mercury column one square
millimeter in section, and 106.3 centimeters long at 0º C. (32º F.)
Synonym--New Ohm.
395 STANDARD ELECTRICAL DICTIONARY.
Ohmic Resistance.
True resistance as distinguished from spurious resistance, or
counter-electro-motive force.
Ohm, Legal.
The practical unit of resistance. The resistance of a column of mercury
one square millimeter in cross-sectional area and 106 centimetres long
at 0º C. (32º F.) The ohm used previously to 1884 is the B. A. Unit of
Resistance, q. v.
One legal ohm = 1.0112 B. A. Units, and I B. A. Unit = 0.9889 legal ohm.
The resistance of a copper wire 1 foot long and 1/1000 inch in diameter
is about 10 ohms. The resistance of 1 mile of iron wire 1/3 inch in
diameter is about 10 ohms.
Synonym--Congress Ohm.
396 STANDARD ELECTRICAL DICTIONARY.

Fig. 252. THEORY OF OHMMETER.