The Standard Electrical Dictionary Part 53

Discharger.

An apparatus for discharging Leyden jars. It consists of a conductor terminating in b.a.l.l.s, and either jointed like a tongs or bent with a spring-action, so that the b.a.l.l.s can be set at distances adapted to different sized jars. It has an insulating handle or a pair of such. In use one ball is brought near to the coating and the other to the spindle ball of the jar. When nearly or quite in contact the jar discharges.

Synonyms--Discharging Rod--Discharging Tongs.

189 STANDARD ELECTRICAL DICTIONARY.

Discharger, Universal.

An apparatus for exposing substances to the static discharge spark. It consists of a base with three insulating posts. The central post carries an ivory table to support the object. The two side posts carry conducting rods, terminating in metal b.a.l.l.s, and mounted with universal joints. A violent shock can be given to any object placed on the table.

Synonym--Henley's Universal Discharger.

Discharge, Silent.

This term is sometimes applied to the glow or brush discharge and sometimes to the condition of electric effluvium. (See Discharge, Brush--Effluvium, Electric.)

Discharge, Spark.

The discontinuous discharge of high tension electricity through a dielectric or into the air produces electric sparks. These are quite strongly luminous, of branching sinuous shape, and in long sparks the luminosity varies in different parts of the same spark. A sharp noise accompanies each spark. High density of charge is requisite for the formation of long sparks.

Disconnection.

The separation of two parts of, or opening a circuit, as by turning a switch, uns.c.r.e.w.i.n.g a binding screw, or the like. The term is sometimes used to indicate a cla.s.s of faults in telegraph circuits. Disconnections may be total, partial or intermittent, and due to many causes, such as open or partially replaced switches, oxidized or dirty contact points, or loose joints.

Displacement, Electric.

A conception of the action of charging a dielectric. The charge is all on the surface. This fact being granted, the theory of displacement holds that charging a body is the displacing of electricity, forcing it from the interior on to the surface, or vice versa, producing a positive or negative charge by displacement of electricity. While displacement is taking place in a dielectric there is a.s.sumed to be a movement or current of electricity called a displacement current.

Disruptive Tension.

When the surface of a body is electrified, it tends to expand, all portions of the surface repelling each other. The film of air surrounding such a body is electrified too, and is subjected to a disruptive tension, varying in intensity with the square of the density.

Dissimulated Electricity.

The electricity of a bound charge. (See Charge, Bound.)

Dissociation.

The separation of a chemical compound into its elements by a sufficiently high degree of heat. All compounds are susceptible of dissociation, so that it follows that combustion is impossible at high temperatures.

190 STANDARD ELECTRICAL DICTIONARY.

Distance, Critical, of Alternative Path.

The length of air gap in an alternative path whose resistance joined to the impedance of the rest of the conductors of the path just balances the impedance of the other path.

Distance, Sparking.

The distance between electrodes, which a spark from a given Leyden jar or other source will pa.s.s across.

Synonym--Explosive Distance.

Distillation.

The evaporation of a liquid by heat, and sometimes in a vacuum, followed by condensation of the vapors, which distil or drop from the end of the condenser. It is claimed that the process is accelerated by the liquid being electrified.

Distributing Box.

In an electric conduit system, a small iron box provided for giving access to the cable for the purpose of making house and minor connections.

Synonym--Hand Hole.

Distributing Switches.

Switch systems for enabling different dynamos to supply different lines of a system as required. Spring jacks, q. v., are used for the lines, and plug switches for the dynamo leads. Thus, dynamos can be thrown in or out as desired, without putting out the lights.

Distribution of Electric Energy, Systems of.

The systems of electric current distribution from central stations or from private generating plants, mechanical or battery, the latter primary or secondary. They include in general the alternating current system and direct current systems. Again, these may be subdivided into series and multiple arc, multiple-series and series-multiple distribution, and the three, four, or five wire system may be applied to multiple arc or multiple series systems. (See Alternating Current--Current System--Multiple Arc--Multiple Series--Series Multiple--Three Wire System.)

Door Opener, Electric.

An apparatus for opening a door by pushing back the latch. A spring then draws the door open, and it is closed against the force of the spring by the person entering. Electro-magnetic mechanism actuates the latch, and is operated by a switch or press-b.u.t.ton. Thus a person on the upper floor can open the hall door without descending.

Dosage, Galvanic.

In electro-therapeutics the amount of electric current or discharge, and duration of treatment given to patients.

Double Carbon Arc Lamp.

An arc lamp designed to burn all night, usually constructed with two parallel sets of carbons, one set replacing the other automatically, the current being switched from the burnt out pair to the other by the action of the mechanism of the lamp.

191 STANDARD ELECTRICAL DICTIONARY.

Double Fluid Theory.

A theory of electricity. Electricity is conveniently treated as a fluid or fluids. According to the double fluid hypothesis negative electricity is due to a preponderance of negative fluid and vice versa. Like fluid repels like, and unlike attracts unlike; either fluid is attracted by matter; the presence in a body of one or the other induces electrification; united in equal proportions they neutralize each other, and friction, chemical decomposition and other causes effect their separation. The hypothesis, while convenient, is overshadowed by the certainty that electricity is not really a fluid at all. (See Single Fluid Theory--Fluid, Electric.)

Synonym--Symmer's Theory.

[Transcriber's note: Current is the motion of negative electrons in a conductor or plasma. Unequal distribution of electrons is static electricity. The relatively immobile nuclei of atoms are positive when one or more of its electrons is absent and accounts for part of the current in electrolysis and plasmas.]

Double Fluid Voltaic Cell.