L
Laminated. Made up of thin plates, as an armature-core.
Laminated Core. (See [Core, Laminated].)
Lamp-Arc. A lamp in which the light is produced by a voltaic arc. Carbon electrodes are used, and a special mechanism operates and regulates the space between the carbons so that a perfect arc may be maintained.
Lamp, Incandescent. A lamp in which the light is produced through heating a filament to whiteness by the electric current. It consists of a glass bulb from which the air is exhausted and sealed, after the filament is enclosed. The ends of the filament are attached to platinum wires, which in turn are made fast to the contact-plates at the head of the lamp, so as to connect with the current.
Lamp-socket. A receptacle for an incandescent lamp. It is generally made of brass and provided with a key-switch to turn the current on and off.
Latent Electricity. (See [Electricity, Latent].)
Lead. (Not the metal.) An insulated conductor which leads to and from a source of power; an insulated conductor to and from a telegraph or telephone instrument; a circuit, a battery, or a station. Not a part of the line circuit.
That part of an electric light or power circuit which leads from the main to the lamps or motors.
Leading-in Wires. The wires which lead into a building from an aerial circuit.
The wires which lead in and out from a lamp, battery, or instrument.
Leak. An escape of electrical energy through leakage. This is more liable to occur in bare than in insulated wires. The escape of current from bare trolley wires is much greater than that from the insulated conductors, particularly in damp or rainy weather.
Leclanché Battery. (See [Battery, Leclanché].)
Leyden-jar. A type of static condenser. Its usual form is a glass jar. Tin-foil is pasted about its inner and outer surfaces covering about half the wall. The balance of the glass is painted with shellac or insulating varnish. The mouth is closed with a cork stopper, and through its centre a brass rod is passed which, by a short chain, is connected with the interior coating of the jar. The top of the rod is provided with a brass knob or ball, and from this last the spark is drawn.
Lightning. The electro-static discharge of clouds floating in the atmosphere. It is the highest form of frictional electricity, uncontrollable and very dangerous, since the strength of a single flash may run into hundreds of thousands of volts.
Lightning-arrester. An apparatus for use with electric lines to carry off to earth any lightning discharges that such lines may pick up; or it may be a form of fuse which burns out before the current can do any harm to the electrical mechanism.
Line-insulator. An insulator serving to support an aerial line.
Lineman. A workman whose business is the practical part of electrical construction in lines and conducting circuits.
Link-fuse. A plate of fusible metal in the shape of a link. It is used as a safety-fuse in connection with copper terminals.
Liquefaction, Electric. The conversion of a solid into a liquid by the sole agency of electricity in its heat action upon the solid.
Liquid Resistance. (See [Resistance, Liquid].)
Lithanode. A block of compressed lead binoxide, with platinum connections, for use in a storage battery.
Litharge. Yellow-lead. A chemical form of metallic lead.
Load. In a dynamo, the amperes of current delivered by it under given conditions of speed, etc.
Local Action. In a battery, the loss of current due to impurities in the zinc. The currents may circulate in exceedingly minute circles, but they waste zinc and chemicals and contribute nothing to the efficiency of the battery.
In a dynamo, the loss of energy through the formation of eddy currents in its core or armature, in the pole pieces, or in other conducting bodies.
Lodestone. The scientific name is magnetite. Some samples possess polarity and attract iron; these are called lodestones.
Loop. A portion of a circuit introduced in series into another circuit.
Low Frequency. A frequency (in current vibrations) of comparatively few alternations per second.
Low Potential Current. (See [Current, Low Potential].)
Luminescence. The power or properties some bodies have of giving out light when their molecular mass is excited. For example, phosphorus and radium.
Luminous Heat. The radiation of heat by electric current, which at the same time produces light. For example, the filament in an incandescent lamp.
Luminous Jar. A Leyden-jar whose coatings are of lozenge-shaped pieces of tin-foil between which are very short spaces. When discharged, sparks appear all over the surface where the small plates of metal nearly join.