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

by T. O'Conor Sloane

Fig. 203. AMERICAN TWIST JOINT.
310 STANDARD ELECTRICAL DICTIONARY.
Joint, Britannia.
A joint for uniting the ends of telegraph and electric wires. The ends
of the wires are scraped clean and laid alongside each other for two
inches, the extreme ends being bent up at about right angles to the
wire. A thin wire is wound four or five times around one of the wires,
back of the joint, the winding is then continued over the lapped
portion, and a few more turns are taken around the other single wire.
The whole is then soldered.

Fig. 204. BRITANNIA JOINT.
Joint, Butt.
A joint in belting or in wire in which the ends to be joined are cut off
square across, placed in contact and secured. It ensures even running
when used in belting. Any irregularity in thickness of a belt affects
the speed of the driven pulley. As dynamos are generally driven by
belts, and it is important to drive them at an even speed to prevent
variations in the electro-motive force, butt joints should be used on
belting for them, unless a very perfect lap joint is made, which does
not affect either the thickness or the stiffness of the belt.
When a butt joint is used in wire a sleeve may be used to receive the
abutting ends, which may be secured therein by soldering. This species
of joint has been used on lightning rods and may more properly be termed
a sleeve joint.
Joint, Lap.
(a) In belting a joint in which the ends are overlapped, and riveted or
otherwise secured in place. If made without reducing the thickness of
the ends it is a bad joint for electrical work, as it prevents even
running of machinery to which it is applied. Hence dynamo belts should
be joined by butt joints, or if by lap joints the ends should be shaved
off so that when joined and riveted, there will be no variation in the
thickness of the belt.
(b) In wire lap joints are made by overlapping the ends of the wire and
soldering or otherwise securing. The Britannia joint (see Joint,
Britannia,) may be considered a lap-joint.
Joint, Marriage.
A joint for stranded conductors used for Galende's cables. It is made
somewhat like a sailor's long splice. Each one of the strands is wound
separately into the place whence the opposite strand is unwound and the
ends are cut off so as to abutt. In this way all are smoothly laid in
place and soldering is next applied.

Fig. 205. MARRIAGE JOINT.
311 STANDARD ELECTRICAL DICTIONARY.
Joint, Sleeve.
A joint in electric conductors, in which the ends of the wires are
inserted into and secured in a metallic sleeve or tube, whose internal
diameter is just sufficient to admit them.
Joint, Splayed.
The method of joining the ends of stranded conductors. The insulating
covering is removed, the wires are opened out, and the center wire,
heart or core of the cable is cut off short. The two ends are brought
together, the opened out wires are interlaced or crotched like the
fingers of the two hands, and the ends are wound around the body of the
cable in opposite directions. The joint is trimmed and well soldered.
Tinned wire with rosin flux for the soldering is to be recommended.
Insulating material is finally applied by hand, with heat if necessary.
Joints in Belts.
Belt-joints for electric plants where the belts drive dynamos should be
made with special care. The least inequality affects the electro-motive
force. Butt joints are, generally speaking, the best, where the ends of
the belt are placed in contact and laced. Lap-joints are made by
overlapping the belt, and unless the belt is carefully tapered so as to
preserve uniform strength, the speed of the dynamo will vary and also
the electromotive force.
Joulad.
A name proposed to be substituted for "joule," q. v. It has not been
adopted.
Joule.
This term has been applied to several units.
(a) The practical C. G. S. unit of electric energy and work--the
volt-coulomb. It is equal to 1E7 ergs--0.73734 foot pound.--.00134 horse
power seconds. A volt-ampere represents one joule per second.
(b) It has also been used as the name of the gram-degree C. thermal
unit--the small calorie.
Synonym--Joulad.
Joule Effect.
The heating effect of a current passing through a conductor. It varies
with the product of the resistance by the square of the current, or with
(C^2)*R.
Joule's Equivalent.
The mechanical equivalent of heat, which if stated in foot-pounds per
pound-degree F. units, is 772 (772.55). (See Equivalents.)
Junction Box.
In underground distribution systems, an iron casing or box in which the
feeders and mains are joined, and where other junctions are made.
Synonym--Fishing Box.

311 STANDARD ELECTRICAL DICTIONARY.
K.
The symbol for electrostatic capacity.
Kaolin.
A product of decomposition of feldspar, consisting approximately of
silica, 45, alumina, 40, water, 15. It was used in electric candles of
the Jablochkoff type as a constituent of the insulating layer or
colombin. Later it was abandoned for another substance, as it was found
that it melted and acted as a conductor.
312 STANDARD ELECTRICAL DICTIONARY.
Kapp Line of Force.
A line of force proposed by Kapp. It is equal to 6,000 C. G. S. lines of
force, and the unit of area is the square inch. Unfortunately it has
been adopted by many manufacturers, but its use should be discouraged,
as it is a departure from the uniform system of units.
One Kapp line per square inch = 930 C. G. S. lines per square
centimeter.
Kathelectrotonus.
A term used in medical electricity or electro-therapeutics to indicate
the increased functional activity induced in a nerve by the proximity of
the kathode of an active circuit which is completed through the nerve.
The converse of anelectrotonus.
Kathode.
The terminal of an electric circuit whence an electrolyzing current
passes from a solution. It is the terminal connected to the zinc plate
of a primary battery.
Kathodic Closure Contraction.
A term in electro-therapeutics; the contractions near where the kathode
of an active circuit is applied to the body, which are observed at the
instant when the circuit is closed.
Kathodic Duration Contraction.
A term in electro-therapeutics; the contraction near where the kathode
of an active circuit is applied to the body for a period of time.
K. C. C.
Abbreviation for Kathodic Closure Contraction, q. v.
K. D. C.
Abbreviation for Kathodic Duration Contraction, q. v.
Keeper.
A bar of soft iron used to connect the opposite poles of a horseshoe
magnet or the opposite poles of two bar magnets placed side by side. It
is designed to prevent loss of magnetism. The armature of a horseshoe
magnet is generally used as its keeper. For bar magnets a keeper is used
for each end, the magnets being laid side by side, with their poles in
opposite direction but not touching, and a keeper laid across at each
end connecting the opposite poles.
Kerr Effect.
The effect of an electrostatic field upon polarized light traversing a
dielectric contained within the field. (See Electrostatic Refraction.)
Kerr's Experiment.
Polarized light reflected from the polished face of a magnet pole has
its plane of polarization rotated; when it is reflected from the north
pole the rotation is from left to right.
313 STANDARD ELECTRICAL DICTIONARY.
Key.
A switch adapted for making and breaking contact easily when worked by
hand, as a Morse telegraph key.
Key Board.
A board or tablet on which keys or switches are mounted.
Key-board.
(a) A switch board, q. v.
(b) A set of lettered keys similar to those of a typewriter employed in
some telegraph instruments. As each key is depressed it produces the
contact or break requisite for the sending of the signal corresponding
to the letter marked upon the key. The signal in printing telegraphs, on
which such key-boards are used, is the reprinting of the letter at the
distant end of the line.
Key, Bridge.
A key for use with a Wheatstone Bridge, q.v. It is desirable to first
send a current through the four arms of the bridge in using it for
testing resistances and then through the galvanometer, because it takes
a definite time for the current to reach its full strength. This is
especially the case if the element being measured has high static
capacity, as a long ocean cable. If the galvanometer connections were
completed simultaneously with the bridge connections a momentary swing
would be produced even if the arms bore the proper relation to each
other. This would cause delay in the testing. A bridge key avoids this
by first connecting the battery circuit through the arms of the bridge,
and then as it is still further depressed the galvanometer circuit is
completed.
314 STANDARD ELECTRICAL DICTIONARY.

Fig. 206. CHARGE AND DISCHARGE KEY
Key, Charge and Discharge.
A key for use in observing the discharge of a condenser immediately
after removing the battery. In one typical form it has two contacts, one
below and one above, and being a spring in itself is pressed up against
the upper one. Connections are so made that when in its upper position
it brings the two coatings of the condenser in circuit with the
galvanometer. When depressed it does the same for a battery. In use it
is depressed and suddenly released when the galvanometer receives the
full charge, before there has been time for leakage. This is one method
of connection illustrating its principle.
In the cut L is the spring-key proper. S2, is the upper contact screw
against which the spring normally presses. In this position the
galvanometer G is in circuit with the opposite coatings of the condenser
C. On depressing the contact S2, is broken and S1, is made. This brings
the battery B in circuit with the condenser coatings. On releasing the
key it springs up and the galvanometer receives the effect of the charge
of the condenser as derived from the battery.
Key, Double Contact.
A key arranged to close two distinct circuits, holding the first closed
until the second is completed. It is used for Wheatstone bridge work.
Key, Double Tapper.
A telegraph key giving contacts alternately for currents in opposite
directions, used in needle telegraphy.
Key, Increment.
A key for use in duplex and quadruplex telegraphy. Its action is to
increase the line current, not merely to suddenly turn current into it.
315 STANDARD ELECTRICAL DICTIONARY.