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Magnet. A substance or metal having the power to attract iron and steel.
Magnet-bar. A magnet in the shape of a straight bar. (See [Bar-magnet].)
Magnet-coil. A coil of insulated wire enclosing a core of soft iron through which a current of electricity is passed to magnetize the iron.
Magnet-core. An iron bar or mass of iron around which insulated wire is wound in order to create an electro-magnet.
Magnet, Electric. A magnet consisting of a bar of iron, a bundle of iron wires, or an iron tube, around which a coil of insulated wire is wound. When a current is passing through the coil its influence magnetizes the iron core, but directly the current ceases the magnetism disappears.
Magnet, Field. The electro or permanent magnet in a dynamo or motor, used to produce the area of electric energy.
Magnet, Horseshoe. A magnet of U shape with the poles or ends brought closer together than the other parts of the limbs. A soft iron bar is placed across the poles when not in use, as this serves to conserve the magnetism.
Magnet, Permanent. A term applied to a hard steel magnet possessing high retentivity, or the power to hold its magnetism indefinitely.
Magnet, Regulator. An electro-magnet whose armature moves in such a manner as to automatically shift the commutator-brushes, on a motor or dynamo, to a position which insures the preservation of both brushes and commutator-bars, and also produces a constant current.
Magnet, Simple. A magnet made of one piece of metal.
Magnet Wire. Insulated wire used for coils. Cotton or silk covered wire is the most serviceable for winding magnets.
Magnetic Adherence. The tendency of a mass of iron to adhere to the poles of a magnet.
Magnetic Attraction and Repulsion. The attraction of a magnet for iron, steel, nickel, and cobalt; also of unlike poles of magnets for each other. The like poles repel.
Magnetic Circuit-breakers. An automatic switch, or breaker, whose action is excited and controlled by an electro-magnet.
Magnetic Concentration of Ores. The separation of iron and steel from their gangue by magnetic attraction. It is applicable only when either the ore or the gangue is susceptible to the magnet.
Magnetic Control. The control of a magnetic needle, magnet, index, armature, or other iron indicator in a galvanometer, ammeter, or voltmeter by a magnetic field.
Magnetic Dip. The inclination from the horizontal position of a magnetic needle that is free to move in a vertical plane.
Magnetic Field, Rotary. A magnetic field resulting from a rotary current.
Magnetic Field, Shifting. A magnetic field which rotates. Its lines of magnetic force vary, therefore, in position.
Magnetic Field, Uniform. A field of uniform strength in all portions, such as the magnetic field of the earth.
Magnetic Force. The power of attraction and repulsion exercised by a magnet; the force of attraction and repulsion which a magnet exercises, and which, in its ultimate essence, is unknown to science.
Magnetic Induction. (See [Induction, Magnetic].)
Magnetic Needle. A magnet having a cup or small depression at its centre, and poised on a sharp pin of brass, so as to be free to rotate. Its N pole points to the north, and its S pole to the south. A compass needle.
Magnetic Poles. The terrestrial points towards which the north or south poles of the magnetic needle are attracted. There are two poles: the arctic, or negative, which attracts the positive or N pole of the magnetic needle; and the antarctic, or positive, which attracts the S pole of the needle.
Magnetic Poles, False. It has been established that there are other poles on the earth that attract the magnetic needle when the latter is brought into their vicinity. These are called false poles, and are probably caused by large deposits of iron lying close to the surface of the earth.
Magnetic Separator. An apparatus for separating magnetic substances from mixtures. It is used chiefly in separating iron ore from earth and rock. The mineral falls on an iron cylinder, or drum, magnetized by coils, and adheres there, while the earth or crushed rock drops below. The particles of iron are afterwards removed by a scraper. The machine is also used in separating iron filings and chips from brass, copper, or other metals, the iron adhering to the magnet, while the brass and other chips drop underneath.
Magnetism. The phenomena of attraction exerted by one body for another. It has been commonly understood that magnetism and electricity are very closely related, for without electricity magnetism could not exist, although it has not been shown clearly that magnetism plays any part in the generation of electricity. Magnetism is the phenomenal force exerted by one body having two poles (negative and positive) for like bodies. The horseshoe magnet or a bar of magnetized steel are the simplest examples of this. If both ends of the horseshoe were positive they would not attract, but would repel. If both ends of a bar were positive they would repel; but as one is negative, or north-seeking, and the other positive, they exert lines of force which attract like bodies, such as bits of iron, nails, and needles. No energy is required to maintain magnetism in a tempered steel object, such as the wiring about a soft iron core when it has been magnetized, but electric current must flow about the soft iron core in order to render it a magnet. So soon as the current ceases to flow the magnetism ceases and the soft iron fails to attract.
Magnetism, Uniform. Magnetism that is uniform throughout a mass of magnetic steel, or a core that is electro-magnetic.
Magnetize. To impart magnetic property to a substance capable of receiving it.
Magnetizing-coil. (See [Coil, Magnetizing].)
Magneto Call-bell. A call-bell used principally in telephone systems, and operated by a current from a magneto-electric generator. The current is excited by turning the handle at the side of the telephone-box before removing the receiver from the hook.
Magneto-generator. A current-generator composed of a permanent magnet and a revolving armature which is rotated between the poles of the permanent magnet.
Main Circuit. (See [Circuit, Main].)
Main Feeder. The main wire in a district to which all the feeder wires are attached.
Main Switch. The switch connected to the main wire of a line, or the main-switch controlling a number of auxiliary switches.
Mains, Electric. The large conductors in a system of electric light or power distribution.
Make and Break, Automatic. An apparatus which enables the armature of a magnet to make and break its circuit automatically.
Make-and-break Current. (See [Current, Make-and-break].)
Mercurial Air-pump. An air-pump operated by mercury to obtain a high vacuum, and used extensively for exhausting incandescent-lamp bulbs.
Mercury Tube. A glass tube sealed and containing mercury. It is so arranged as to give out fluorescent light when shaken or agitated by an electric current. For example, the Geissler tubes, the Cooper-Hewitt light, Crook’s tubes, etc.
Metallic Arc. An arc which forms between metallic electrodes.
Metallic Circuit. (See [Circuit, Metallic].)
Metallic Conductor. A conductor composed of a metal.
Metallic Filament. A metal wire used in an incandescent lamp—the filament.
Metallic Resistance. (See [Resistance, Metallic].)
Metallurgy. The art of working metals. Electro-metallurgy applies to the processes wherein electricity plays the most important part.
Mica. A natural mineral of sheet form and translucent, used extensively as an insulator in electrical equipment and mechanism.
Mica, Moulded. A composition composed of ground mica and shellac as a binder. When heated and pressed into various shapes and forms, it is a valuable insulator, and is employed for hooks, locks, tubes, sockets, and the like.
Micanite. An insulating material made by cementing laminations of pure mica together and cementing them with shellac or other suitable non-conducting adhesives.
Molecular Adhesion. The attraction of similar molecules for each other.
Molecular Attraction. The attraction of molecules, or physical affinity.
Molecular Resistance. The resistance which a mass or electrolyte offers when contained in an insulated vessel and a current of electricity is passed through it.
Molecule. One of the invisible particles supposed to constitute matter of every kind; the smallest particle of matter that can exist independently. It is made up of atoms, but an atom cannot exist alone.
Morse Receiver. The receiving instrument once universally used in the Morse system of telegraphy, but now superseded by the sounder.
Morse Recorder. An apparatus which automatically records on a ribbon of paper the dots and dashes of the Morse telegraph alphabet.
Morse Sounder. An electro-magnetic instrument designed to make a sharp, clicking sound when its armature lever is drawn down by the attraction of the magnets.
Morse System. A telegraphic system invented by Prof. S. F. B. Morse, in which, by means of alternating makes and breaks of varying duration, the dots and dashes of the Morse alphabet are reproduced and received at a distance through the agency of wires and the electro-magnetic sounder.
Motor, Electric. A machine or apparatus for converting electric energy into mechanical kinetic energy or power. The electrical energy is usually generated by a dynamo, and distributed on conductors to motors located at various points.
Electric motors are of two types—the A-C., or alternating current, and the D-C., or direct current.
Motor-car, Electric. A self-propelling car driven by stored electricity.
Motor-dynamo. A motor driven by a dynamo whose armature is firmly attached or connected to that of the dynamo. It is used for modifying a current. If the dynamo generates an alternating current of high potential, the motor converts it into a direct current of lower voltage but increased amperage.
Motor-transformer. A transformer which is operated by a motor.
A dynamo-electric machine provided with two armature windings, one serving to receive current, as a motor, the other to deliver current, as a generator, to a secondary circuit.