The Standard Electrical Dictionary Part 87

Installation.

The entire apparatus, buildings and appurtenances of a technical or manufacturing establishment. An electric light installation, for instance, would include the generating plant, any special buildings, the mains and lamps.

Insulating Stool.

A support for a person, used in experiments with static generators. It has ordinarily a wooden top and gla.s.s legs. It separates one standing on it from the earth and enables his surface to receive an electrostatic charge. This tends to make his hair stand on end, and anyone on the floor who touches him will receive a shock.

Insulating Tape.

Prepared tape used in covering the ends of wire where stripped for making joints. After the stripped ends of two pieces are twisted together, and if necessary soldered and carefully cleaned of soldering fluid, they may be insulated by being wound with insulating tape.

The tape is variously prepared. It may be common cotton or other tape saturated with any insulating compound, or may be a strip of gutta percha or of some flexible cement-like composition.

306 STANDARD ELECTRICAL DICTIONARY.

Insulating Varnish.

Varnish used to coat the surface of gla.s.s electrical apparatus, to prevent the deposition of hygrometric moisture, and also in the construction of magnetizing and induction coils and the like. Sh.e.l.lac dissolved in alcohol is much used. Gum copal dissolved in ether is another. A solution of sealing wax in alcohol is also used. If applied in quant.i.ties these may need baking to bring about the last drying. (See Sh.e.l.lac Varnish.)

Insulator.

(a) Any insulating substance.

(b) A telegraph or line insulator for telegraph wires. (See Insulator, Line or Telegraph.)

Synonyms--Dielectric--Non-conductor.

Insulator Cap.

A covering or hood, generally of iron, placed over an insulator to protect it from injury by fracture with stones or missiles.

Insulator, Fluid.

(a) For very high potentials, as in induction coils or alternating circuits, fluid insulators, such as petroleum or resin oil, have been used. Their princ.i.p.al merit is that if a discharge does take place through them the opening at once closes, so that they are self-healing.

(b) Also a form of telegraph or line insulator in which the lower rim is turned up and inwards, so as to form an annular cup which is filled with oil.

Insulator, Line or Telegraph.

A support often in the shape of a collar or cap, for a telegraph or other wire, made of insulating material. Gla.s.s is generally used in the United States, porcelain is adopted for special cases; pottery or stone ware insulators have been used a great deal in other countries.

Sometimes the insulator is an iron hook set into a gla.s.s screw, which is inserted into a hole in a telegraph bracket. Sometimes a hook is caused to depend from the interior of an inverted cup and the s.p.a.ce between the shank of the hook and cup is filled with paraffine run in while melted.

Insulators are tested by measuring their resistance while immersed in a vessel of water.

Intensity. Strength.

The intensity of a current or its amperage or strength; the intensity or strength of a magnetic field or its magnetic density; the intensity or strength of a light are examples of its use. In the case of dynamic electricity it must be distinguished from tension. The latter corresponds to potential difference or voltage and is not an attribute of current; intensity has no reference to potential and is a characteristic of current.

Intensity of a Magnetic Field.

The intensity of a magnetic field at any point is measured by the force with which it acts on a unit magnet pole placed at that point. Hence unit intensity of field is that intensity of field which acts on a unit pole with a force of one dyne. (S. P. Thomson.) (See Magnetic Lines of Force.)

307 STANDARD ELECTRICAL DICTIONARY.

Intercrossing.

Crossing a pair of conductors of a metallic circuit from side to side to avoid induction from outside sources.

Intermittent.

Acting at intervals, as an intermittent contact, earth, or grounding of a telegraph wire.

Interpolar Conductor.

A conductor connecting the two poles of a battery or current generator; the external circuit in a galvanic circuit.

Interpolation.

A process used in getting a closer approximation to the truth from two varying observations, as of a galvanometer. The process varies for different cases, but amounts to determining an average or deducing a proportional reading from the discrepant observed ones.

Interrupter.

A circuit breaker. It may be operated by hand or be automatic. (See Circuit Breaker--Circuit Breaker, Automatic--and others.)

Interrupter, Electro-magnetic, for a Tuning Fork.

An apparatus for interrupting a current which pa.s.ses through an electromagnet near and facing one of the limbs of a tuning fork. The circuit is made and broken by the vibrations of another tuning fork through which the current pa.s.ses. The second one is thus made to vibrate, although it may be very far off and may not be in exact unison with the first. The first tuning fork has a contact point on one of its limbs, to close the circuit; it may be one which dips into a mercury cup.

Intrapolar Region.

A term in medical electricity, denoting the part of a nerve through which a current is pa.s.sing.

Ions.

The products of decomposition produced in any given electrolysis are termed ions, the one which appears at the anode or negative electrode is the anion. The electrode connected to the carbon or copper plate of a wet battery is an anode. Thus in the electrolysis of water oxygen is the anion and hydrogen is termed the kation. In this case both anion and kation are elements. In the decomposition of copper sulphate the anion is properly speaking sulphion (S O4), a radical, and the kation is copper, an element. Electro-negative elements or radicals are anions, such as oxygen, sulphion, etc., while electro-positive ones are kations, such as pota.s.sium. Again one substance may be an anion referred to one below it and a kation referred to one above it, in the electro-chemical series, q. v. Anion means the ion which goes to the anode or positive electrode; kation, the ion which goes to the kathode or negative electrode.

[Transcriber's note: An ion is an atom or molecule that has lost or gained one or more valence electrons, giving it a positive or negative electrical charge. A negatively charged ion, with more electrons than protons in its nuclei, is an anion. A positively charged ion, with fewer electrons than protons, is a cation. The electron was discovered five years after this publication.]

308 STANDARD ELECTRICAL DICTIONARY.

Iron.

A metal; one of the elements; symbol, Fe; atomic weight, 56; equivalent, 28 and 14, ; valency, 4 and 2.

It is a conductor of electricity. The following data are at 0? C. 32? F., with annealed metal.

Specific Resistance, 9.716 microhms.

Relative Resistance. 6.460 Resistance of a wire, (a) 1 foot long weighing 1 grain, 1.085 ohms.