The Standard Electrical Dictionary Part 86

A term formerly used to express the phenomenon of the alternative discharge of a Leyden jar or other oscillatory discharge of electricity.

(See Discharge, Alternative.)

Induction, Magnetic.

The magnetization of iron or other paramagnetic substance by a magnetic field.

On account of its permeability or multiplying power for lines of force, a paramagnetic body always concentrates lines of force in itself if placed in a magnetic field, and hence becomes for the time being a magnet, or is said to be polarized.

As the tendency of lines of force is to follow the most permeable path, a paramagnetic bar places itself lengthwise or parallel with the prevailing direction of the lines of force so as to carry them as far on their way as possible. Every other position of the bar is one of unstable equilibrium or of no equilibrium. The end of the bar where the lines of force enter (see Lines of Force) is a south pole and is attracted towards the north pole of the magnet.

The production of magnetic poles under these conditions in the bar is shown by throwing iron filings upon it. They adhere to both ends but not to the middle.

Induction, Mutual, Electro-magnetic.

The induction due to two electric currents reacting on each other.

303 STANDARD ELECTRICAL DICTIONARY.

Induction, Mutual, Electrostatic.

A charged body always induces a charge upon any other body near it; and the same charge in the second body will induce the other charge in the first body if the latter is unexcited. In other words the second body's induction from the first is the measure of the charge the second would require to induce in the first its own (the second's) induced charge.

This is the law of mutual electrostatic induction.

Induction, Open Circuit.

Inductive effects produced in open circuits. By oscillatory discharges a discharge can be produced across a break in a circuit otherwise complete. The requirements for its production involve a correspondence or relation of its dimensions to the inducing discharge. The whole is a.n.a.logous to the phenomena of sound resonators and sympathetic vibrations. Synonym--Oscillatory induction.

Induction, Self-.

(a) A phenomenon of electric currents a.n.a.logous to the inertia of matter. Just as water which fills a pipe would resist a sudden change in its rate of motion, whether to start from rest, to cease or decrease its motion, so an electric current requires an appreciable time to start and stop. It is produced most strongly in a coiled conductor, especially if a core of iron is contained within it.

As in the case of two parallel wires, one bearing currents which vary, momentary currents are induced in the other wire, so in a single conductor a species of inertia is found which r.e.t.a.r.ds and prolongs the current. If a single conductor is twisted into a helix or corresponding shape, its separate turns react one on the other in accordance with the general principles of electromagnetic induction. (See Induction, Electro-magnetic.) Thus when a current is suddenly formed the coils acting upon each other r.e.t.a.r.d for an instant its pa.s.sage, producing the effect of a reverse induced current or extra current opposing the princ.i.p.al current. Of course no extra current is perceptible, but only the diminution. When the current is pa.s.sing regularly and the current is broken, the corresponding action prolongs the current or rather intensifies it for an instant, producing the true extra current. This is current self-induction.

[Transcriber's note: See inductance.]

Synonyms--Electric Inertia--Electro-dynamic Capacity.

(b) A permanent magnet is said to tend to repel its own magnetism, and thus to weaken itself; the tendency is due to magnetic self-induction.

Induction Sheath.

In the brush dynamo a thin sheet of copper surrounding the magnet cores with edges soldered together. The winding is outside of it. Its object is to absorb extra currents set up by variations in magnetic intensity in the cores. These currents otherwise would circulate in the cores.

304 STANDARD ELECTRICAL DICTIONARY.

Induction, Unit of Self-.

The unit of self-induction is the same as that of induction in general.

It is the henry, q. v.

Induction, Unipolar.

Induction produced in a conductor which continuously cuts the lines of force issuing from one pole of a magnet. As the lines of force are always cut in the same sense a continuous and constant direction current is produced.

Induction, Vertical.

In an iron or steel s.h.i.+p the induction or attraction exercised in the compa.s.s by vertical elements of the structure. Such vertical ma.s.ses of iron in the northern hemisphere would have their upper ends polarized as south poles, and would affect the magnet as soon as the vessel swung out of the magnetic meridian. Thus this induction disappears twice in swinging a s.h.i.+p through a complete circle; deviation due to it is termed semi-circular deviation. (See Deviation, Semi-circular.)

Fig. 202. INDUCTOR DYNAMO.

Inductophone.

A method of train telegraphy. The train carries a circuit including a coil, and messages are picked up by it from coils along the line into which an alternating current is pa.s.sed. A telephone is used as a receiver in place of a sounder or relay. The invention, never practically used, is due to Willoughby Smith.

305 STANDARD ELECTRICAL DICTIONARY.

Inductor.

(a) In a current generator a ma.s.s of iron, generally laminated, which is moved past a magnet pole to increase the number of lines of force issuing therefrom. It is used in inductor dynamos. (See Dynamo Inductor.) In the cut Fig. 202, of an inductor dynamo i, i, are the laminated inductors.

(b) In influence machines the paper or tinfoil armatures on which the electrification is induced.

Inertia.

A force in virtue of which every body persists in its state of motion or rest except so far as it is acted on by some force.

Inertia, Electro-magnetic.

This term is sometimes applied to the phenomena of self-induction, or rather to the cause of these phenomena.

Infinity Plug.

A plug in a resistance box, which on being pulled out of its seat opens the circuit or makes it of infinite resistance. The plug seats itself between two bra.s.s plates which are not connected with each other in any way. The other plates are connected by resistance coils of varying resistance.

Influence, Electric.

Electric induction, which may be either electrostatic, current, or electro-magnetic.

Insolation, Electric.

Exposure to powerful arc-light produces effects resembling those of sun-stroke. The above term or the term "electric sun-stroke" has been applied to them.

[Transcriber's note: Operators of arc welders are p.r.o.ne to skin cancer from ultra violet rays if not properly protected.]