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

by T. O'Conor Sloane

Fig. 207. KEMPE'S DISCHARGE KEY.
Key, Kempe's Discharge.
A key giving a charging, discharging and insulating connection, for
static condenser work. Referring to the cut l is a lever or spring with
upper discharging contact s, and lower charging contact s'. In use it is
pressed down by the insulating handle or finger piece C, until caught by
the hook attached to the key I. This hook is lower down than that on the
key D, and holds it in contact with the charging contact piece S'. On
pressing the key I, marked or designated "Insulate," it springs up,
breaks contact at S', and catching against the hook on D, which key is
designated "Discharge," remains insulated from both contacts; next on
pressing D it is released and springs up and closes the discharge
contact S. It is a form of charge and discharge key. (See Key, Charge
and Discharge.)
Key, Magneto-electric.
A telegraph key whose movements operate what is virtually a small
magneto-generator, so as to produce currents of alternating direction,
one impulse for each motion of the key. It is employed for telegraphing
without a line battery, a polarized relay being used. In one very simple
form a key is mounted on a base with a permanent magnet and connected to
the armature, so that when the key is pressed downwards it draws the
armature away from the poles of the magnet. If the magnet or its
armature is wound with insulated wire this action of the key will cause
instantaneous currents to go through a circuit connected to the magnet
or armature coils.

Fig. 208. SIEMENS' MAGNETO-ELECTRIC KEY.
In Siemens & Halske's key an H armature E is pivoted between the poles N
S, of a powerful compound horseshoe magnet, G G. It is wound with fine
wire and a key handle H is provided for working it. In its normal
position the handle is drawn upward, and the end S S of the armature
core is in contact with the south pole S of the permanent magnet, and
the end D D with the north pole. This establishes the polarity of the
armature. On depressing the key the contacts are broken and in their
place the end D D comes in contact with the south pole and the end S S
with the north pole. This suddenly reverses the polarity of the armature
and sends a momentary current through the armature coil which is in
circuit with the line. The cut only shows the principle of the key,
whose construction is quite complicated.
316 STANDARD ELECTRICAL DICTIONARY.
Key, Make and Break.
An ordinary electric key, usually making a contact when depressed, and
rising by spring action when released, and in its rise breaking the
contact.

Fig. 209. PLUG KEY
Key, Plug.
An appliance for closing a circuit. Two brass blocks are connected to
the terminals, but are disconnected from each other. A brass plug
slightly coned or with its end split so as to give it spring action is
thrust between the blocks to complete the circuit. It is used in
Resistance coils and elsewhere. (See Coil, Resistance.) Grooves are
formed in the blocks to receive the plug.
Key, Reversing.
(a) A double key, arranged so that by depressing one key a current flows
in one direction, and by depressing the other a current flows in the
opposite direction. It is used in connection with a galvanometer in
experimental, testing or measuring operations.
(b) A key effecting the same result used in quadruplex telegraphy.
Key, Sliding-Contact.
A name given to the key used for making instantaneous contacts with the
metre wire of a metre bridge, q. v. The name is not strictly correct,
because it is important that there should be no sliding contact made, as
it would wear out the wire and make it of uneven resistance.
It is a key which slides along over the wire and which, when depressed,
presses a platinum tipped knife edge upon the wire. On being released
from pressure the key handle springs up and takes the knife edge off the
wire. This removal is essential to avoid wearing the wire, whose
resistance per unit of length must be absolutely uniform.
Key, Telegraph.
The key used in telegraphy for sending currents as desired over the
line. It consists of a pivoted lever with finger piece, which lever when
depressed makes contact between a contact point on its end and a
stationary contact point on the base. This closes the circuit through
the line. When released it springs up and opens the line circuit.
Kilo.
A prefix to the names of units; it indicates one thousand times, as
kilogram, one thousand grams. A few such units are given below.
Kilodyne.
A compound unit; one thousand dynes. (See Dyne.)
Kilogram.
A compound unit; one thousand grams; 2.2046 pounds avds.
317 STANDARD ELECTRICAL DICTIONARY.
Kilojoule.
A compound unit; one thousand joules, q. v.
Kilometer.
A compound unit; one thousand meters; 3280.899 feet; 0.621382 statute
miles. (See Meter.)
Kilowatt.
A compound unit; one thousand watts, q. v.
Kine.
An absolute or C. G. S. unit of velocity or rate of motion; one
centimeter per second; proposed by the British Association.
Kirchoff's Laws.
These relate to divided circuits.
I. When a steady current branches, the quantity of electricity arriving
by the single wire is equal to the quantity leaving the junction by the
branches. The algebraical sum of the intensities of the currents passing
towards (or passing from) the junction is equal to zero; Summation(C) =
0 (Daniell.) In the last sentence currents flowing towards the point are
considered of one sign and those flowing away from it of the other.
II. In a metallic circuit comprising within it a source of permanent
difference of potential, E, the products of the intensity of the current
within each part of the circuit into the corresponding resistance are,
if the elements of current be all taken in cyclical order together,
equal to E; Summation(C * r) =E. In a metallic circuit in which there is
no source of permanent difference of potential E = 0, and Summation(C *
r) = 0.
This law applies to each several mesh of a wire network as well as to a
single metallic loop, and it holds good even when an extraneous current
is passed through the loop. (Daniell.)
In this statement of the two laws E stands for electro-motive force, C
for current intensity; and r for resistance of a single member of the
circuit.
[Transcriber's note: These laws may be restated as: At any point in an
steady-state electrical circuit, the directed sum of currents flowing
towards that point is zero. The directed sum of the electrical potential
differences around any closed circuit is zero.]
Knife-edge Suspension.
The suspension of an object on a sharp edge of steel or agate. The knife
edge should abut against a plane. The knife edge is generally carried by
the poised object. Its edge then faces downward and on the support one
or more plane or approximately plane surfaces are provided on which it
rests. In the ordinary balance this suspension can be seen. It is
sometimes used in the dipping needle.
It is applied in cases where vertical oscillations are to be provided
for.
Knot.
The geographical mile; a term derived from the knots on the log line,
used by navigators. It is equal to 6,087 feet.
Synonyms--Nautical Mile--Geographical Mile.
[Transcriber's note: A knot is a velocity, 1 nautical mile per hour, not
a distance. The contemporary definition is: 1 international knot = 1
nautical mile per hour = 1.852 kilometres per hour = 1.1507794 miles per
hour = 0.51444444 meters per second = 6076.1152 feet per hour.]
318 STANDARD ELECTRICAL DICTIONARY.
Kohlrausch's Law.
A law of the rate of travel of the elements and radicals in solutions
under the effects of electrolysis. It states that each element under the
effects of electrolysis has a rate of travel for a given liquid, which
is independent of the element with which it was combined. The rates of
travel are stated for different elements in centimeters per hour for a
potential difference of one or more volts per centimeter of path.
[Friedrich Wilhelm Georg Kohlrausch (1840-1910)]
Kookogey's Solution.
An acid exciting and depolarizing solution for a zinc-carbon couple,
such as a Bunsen battery. Its formula is: Potassium bichromate, 227
parts; water, boiling, 1,134 parts; while boiling add very carefully and
slowly 1,558 parts concentrated sulphuric acid. All parts are by weight.
Use cold.
Krizik's Cores.
Cores of iron for use with magnetizing coils, q. v. They are so shaped,
the metal increasing in quantity per unit of length, as the centre is
approached, that the pull of the excited coil upon them will as far as
possible be equal in all positions. A uniform cylinder is attracted with
varying force according to its position; the Krizik bars or cores are
attracted approximately uniformly through a considerable range.

318 STANDARD ELECTRICAL DICTIONARY.
L.
Symbol for length and also for the unit of inductance or coefficient of
induction, because the dimensions of inductance are length.
Lag, Angle of.
(a) The angle of displacement of the magnetic axis of an armature of a
dynamo, due to its magnetic lag. The axis of magnetism is displaced in
the direction of rotation. (See Magnetic Lag.)
(b) The angle expressing the lag of alternating current and
electro-motive force phases.
Laminated. adj.
Made up of thin plates, as a laminated armature core or converter core.
Lamination.
The building up of an armature core or other thing out of plates. The
cores of dynamo armatures or of alternating current converters are often
laminated. Thus a drum armature core may consist of a quantity of thin
iron discs, strung upon a rod and rigidly secured, either with or
without paper insulation between the discs. If no paper is used the film
of oxide on the iron is relied on for insulation. The object of
lamination is to break up the electrical continuity of the core, so as
to avoid Foucault currents. (See Currents, Foucault.) The laminations
should be at right angles to the direction of the Foucault currents
which would be produced, or in most cases should be at right angles to
the active parts of the wire windings.
319 STANDARD ELECTRICAL DICTIONARY.
Lamination of Armature Conductors.
These are sometimes laminated to prevent the formation of eddy currents.
The lamination should be radial, and the strips composing it should be
insulated from each other by superficial oxidation, oiling or
enamelling, and should be united only at their ends.

Fig. 210. PILSEN ARC LAMP.
Lamp, Arc.
A lamp in which the light is produced by a voltaic arc. Carbon
electrodes are almost universally employed. Special mechanism, operating
partly by spring or gravity and partly by electricity, is employed to
regulate the distance apart of the carbons, to let them touch when no
current passes, and to separate them when current is first turned on.
The most varied constructions have been employed, examples of which will
be found in their places. Lamps may in general be divided into classes
as follows, according to their regulating mechanism and other features:
(a) Single light regulators or monophotes. Lamps through whose
regulating mechanism the whole current passes. These are only adapted to
work singly; if several are placed in series on the same circuit, the
action of one regulator interferes with that of the next one.
(b) Multiple light regulators or polyphotes. In these the regulating
mechanism and the carbons with their arc are in parallel; the regulating
device may be a single magnet or solenoid constituting a derived or
shunt-circuit lamp, or it may include two magnets working differentially
against or in opposition to each other constituting a differential lamp.
320 STANDARD ELECTRICAL DICTIONARY.
(c) Lamps with fixed parallel carbons termed candles (q. v., of various
types).
(d) Lamps without regulating mechanism. These include lamps with
converging carbons, whose object was to dispense with the regulating
mechanism, but which in some cases have about as much regulating
mechanism as any of the ordinary arc lamps.
Lamp, Contact.
A lamp depending for its action on loose contact between two carbon
electrodes. At the contact a species of incandescence with incipient
arcs is produced. One of the electrodes is usually flat or nearly so,
and the other one of pencil shape rests upon it.
Lamp, Differential Arc.
An arc lamp, the regulation of the distance between whose carbons
depends on the differential action of two separate electrical coils. The
diagram illustrates the principle. The two carbons are seen in black;
the upper one is movable, The current arrives at A. It divides, and the
greater part goes through the low resistance coil M to a contact roller
r, and thence by the frame to the upper carbon, and through the arc and
lower carbon to B, where it leaves the lamp. A smaller portion of the
current goes through the coil M1 of higher resistance and leaves the
lamp also at B. A double conical iron core is seen, to which the upper
carbon holder is attached. This is attracted in opposite directions by
the two coils. If the arc grows too long its resistance increases and
the coil M1 receiving more current draws it down and thus shortens the
arc. If the arc grows too short, its resistance falls, and the coil M
receives more current and draws the core upwards, thus lengthening the
arc. This differential action of the two cores gives the lamp its name.
R is a pulley over which a cord passes, one end attached to the core and
the other to a counterpoise weight, W.

Fig. 211. DIAGRAM OF THE PILSEN DIFFERENTIAL ARC LAMP.
321 STANDARD ELECTRICAL DICTIONARY.
Lamp, Holophote.
A lamp designed for use alone upon its own circuit. These have the
regulating mechanism in series with the carbon and arc, so that the
whole current goes through both. (See Lamp, Arc.)
Synonym--Monophote Lamp.
Lamp-hour.
A unit of commercial supply of electric energy; the volt-coulombs
required to maintain an electric lamp for one hour. A sixteen-candle
power incandescent lamp is practically the lamp alluded to, and requires
about half an ampere current at 110 volts, making a lamp-hour equal to
about 198,000 volt-coulombs.
[Transcriber's note: 0.55 KW hours.]
Lamp, Incandescent.
An electric lamp in which the light is produced by heating to whiteness
a refractory conductor by the passage of a current of electricity. It is
distinguished from an arc lamp (which etymologically is also an
incandescent lamp) by the absence of any break in the continuity of its
refractory conductor. Many different forms and methods of construction
have been tried, but now all have settled into approximately the same
type.
The incandescent lamp consists of a small glass bulb, called the
lamp-chamber, which is exhausted of air and hermetically sealed. It
contains a filament of carbon, bent into a loop of more or less simple
shape. This shape prevents any tensile strain upon the loop and also
approximates to the outline of a regular flame.