The Standard Electrical Dictionary Part 89

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 b.u.t.t 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 ab.u.t.t. 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. b.u.t.t 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 subst.i.tuted 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 pa.s.sing 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--Fis.h.i.+ng Box.

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 const.i.tuent 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 pa.s.ses 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.