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Igniter. A mechanical hand apparatus, in which a battery, induction-coil, and vibrator are located, and whose spark, jumping across a gap at the end of a rod, ignites or lights a gas flame, blasting-powder, or dynamite.
I-H-P. An abbreviation for indicated horse-power.
Illuminating Power. Any source of light as compared with a standard light—as, for instance, the illuminating power of an electric light reckoned in candle-power.
Illumination. A light given from any source and projected on a surface, per unit of area, directly or by reflection. It is stated in terms—as, for instance, the candle-power of a lamp. When speaking of an incandescent lamp we say it illuminates equal to four candle-power or it gives a light equal to sixteen candle-power.
Immersion, Simple. Plating, without the aid of a battery, by simply immersing the metal in a solution of metallic salt.
Impulse. The motion produced by the sudden or momentary action of a force upon a body. An electro-magnetic impulse is the action produced by the electro-magnetic waves in magnetizing a mass of soft iron and attracting to it another mass of iron or steel.
An electro-motive impulse is one where the force rises so high as to produce an impulsive discharge such as that from a Leyden-jar.
Incandescence, Electric. The heating of a conductor to red or white heat by the passage of an electric current. For example, an incandescent lamp.
Incandescent Circuit. (See [Circuit, Incandescent].)
Incandescent Lamp-filament. (See [Filament].)
India-rubber. (See [Caoutchouc] and [Gutta-percha].)
Indicator-card. The card used in galvanoscopes, volt and ampere meters, and other instruments. It is provided with a moving needle and is marked with a graduated scale.
Induced. Caused by induction, and not directly.
Induced Current. (See [Current, Induced].)
Inductance. That capacity of a circuit which enables it to exercise induction and create lines of force.
Inductance is the ratio between the total induction through a circuit to the current producing it.
Induction, Back. A demagnetizing force produced in a dynamo armature when a lead is given to the brushes. When the brushes are so set the windings on the armature are virtually divided into two sets: one a direct magnetizing set, the other a cross-magnetizing set which exerts a demagnetizing action on the other set. The position of the brushes on a dynamo or motor is indicated by their location, and if changed back induction will be the result.
Induction-coil. (See [Coil, Induction].)
Induction, Electro-magnetic. When negative and positive currents are brought towards each other against their material repulsive tendencies the result is work, or energy, and the consequent energy increases the intensity of both currents temporarily. The variations thus temporarily produced in the currents are examples of electro-magnetic induction. A current is surrounded by lines of force. The approach of two circuits—one negative, the other positive—involves a change in the lines of force about the secondary circuit. Lines of force and current are so intimately connected that a change in one compels a change in the other. Therefore, the induced current in the secondary may be attributed to the change in the field of force in which it lies. The inner and outer coils of wire about the soft iron wire composing an induction-coil are the best and simplest examples of electro-magnetic induction.
Induction, Magnetic. The magnetization of iron or other paramagnetic substances by a magnetic field. The magnetic influence of a bar excited under these conditions is shown by throwing iron filings upon it. They will adhere to both ends (that is at the negative and positive poles) but not at the middle.
Inductor. A mass of iron in a current generator which is moved past a magnet-pole to increase the number of lines of force issuing therefrom. It is generally laminated, and is used in inductor dynamos and motors of the alternating-current type.
Influence, Electric. Electric induction or influence which may be electro-static, current, or electro-magnetic.
Influence Machine. A static electric machine worked by induction, and used to build up charges of opposite nature on two separate prime-conductors.
Installation. The entire apparatus, building, and appurtenances of a technical or manufacturing plant or power-house. An electric-light installation would mean the machinery, street-lines, lamps, etc.
Insulating Joint. Used for the purpose of insulating a gas-pipe from an electric circuit.
Insulating Varnish. A varnish composed of insulating material, such as gums, shellac, or diluted rubber. Shellac dissolved in alcohol is perhaps the best. It is easy to make and dries quickly, making an insulating surface practical for almost every ordinary use.
Insulation. The dielectric or non-conducting materials which are used to prevent the leakage of electricity. The covering for magnet wires, and overhead conduits for power lines and electric lighting.
Insulation, Oil. Any non-combustible oil may be employed as an insulator to prevent electrical leakage in induction-coils, transformers, and the like. Its principal advantage lies in its being in liquid form, permitting of easy handling. Moreover, if pierced by a spark from a coil, it at once closes again without becoming ignited. A solid insulator, if pierced, is permanently injured.
Insulator. Any insulating substance or material to prevent the escape of current. The knobs of porcelain or glass to which wires are made fast.
Insulator, Porcelain. An insulator made of porcelain and used to support a wire.
Intensity. The intensity or strength of a current is its amperage. The strength of a magnetic field, its power to attract or magnetize.
Internal Circuit. (See [Circuit, Internal].)
Internal Resistance. (See [Resistance, Internal].)
Interrupter. A circuit-breaker. Any device which breaks or interrupts a circuit. It may be operated by hand or automatically.
The vibrator of an induction-coil.
The commutators of an armature.
Isolated Plant. The system of supplying electric energy by independent generating dynamos for each house, factory, or traction line.
Isolation, Electric. A term applied to “electric sunstroke.” Exposure to powerful arc-light produces effects resembling those of sunstroke.