Horseshoe magnet

“ The permanent steel magnet is used for compass needles, as the familiar horseshoe magnet, and in certain types of electric machinery. The electric magnet forms a part of nearly every kind of electrical machinery and is by far the most useful form of the magnet. The modern high-duty lifting magnet is a form of the electric magnet. ”

“ Nearly every boy has had among his treasured possessions a small horseshoe magnet, painted red, with bright ends, and has spent many happy hours picking up needles, steel pins or other small objects, and finally tired of it because of its small lifting capacity and dreamed of one which would lift a hammer, or possibly even the family flatiron. ”

“ The current traverses the coils of an electro-magnet (E, Fig. 13) , beneath which is a permanent steel horseshoe magnet, having its poles in contact with the soft-iron cores of the electro-magnet. When no current is passing, the influence of the steel renders these cores temporary magnets, and enables them to hold the movable armature (p) against the force of an opposing spring. The current is in such a direction that it tends to reverse the magnetism induced by the steel. ”

“ A pair of horseshoe magnets may thus be regulated in such a way as to form a perfectly astatic system in a uniform field and to preserve an almost invariable zero, this being something that it is very difficult to obtain with the ordinary arrangement of needles, especially when a compensating magnet is used ”

“ Fig. 252.—The Principle of the Alternator and the Direct-Current Dynamo. In the telephone magneto, more than one horseshoe magnet is usually provided. The coil of wire revolves between the poles of the magnets. The coil is wound around an iron frame and together they are called the armature. The end of the armature shaft is fitted with a small spur gear meshing with a larger gear bearing a crank, so that when the crank is turned the motion is multiplied and the armature is caused to revolve rapidly. One end of the coil or armature winding is connected to a small brass pin. ”

“ The horseshoe magnet does not impart its own magnetism to the piece of iron which is rubbed with it, but the electromagnetic energies in the magnet arouse to vibratory activity the latent electromagnetic energies in the iron. ”

“ During the first experiments it often happened that when the weight which the magnet could support had reached its maximum, all on a sudden the horseshoe would become incapable of re-acquiring magnetism, not even so much as to be able to support the keeper again. ”

“ Well, each of them consists of a great iron horseshoe, rendered alternately a magnet and not a magnet by an intermittent current of electricity from a battery, this current in its turn regulated by clock-work. When the horseshoe is in the circuit, it is a magnet, and it pulls its clapper toward it with enormous power. When it is out of the circuit, the next second, it is not a magnet, and it lets the clapper go. ”

“ The apparatus needed is simply a good compound horseshoe permanent magnet, 15 centimeters long, having six or more plates, giving it a total thickness of at least 3 centimeters. We need a sufficiently powerful magnet, as I find that I obtain a more equal distribution of magnetism upon a rod or strip of iron by drawing it lengthwise over a single pole in a direction from that pole, as shown in Fig. 2; we can then obtain saturation by repeated drawings, keeping the same molecular symmetry in each experiment. ”

“ The form usually given to an electro-magnet depends upon the use to which it is to be put. The horseshoe is the most common. This consists of two electro-magnets mounted on a yoke and connected so that the two free poles are North and South.
Fig. 85.—If you wind the Wire around a small Paper Tube into which a Nail will slide easily, the Coil will draw the Nail in when the Current is turned on. Electro-magnets are made on a huge scale for lifting large castings and heavy pieces of iron. Such magnets are used in the great steel mills and in factories where nails, bolts, etc., are manufactured. ”

“ Horse-shoe magnets should have a short bar of soft iron adapted to connect the two poles, and should never be laid by without such a piece of iron adhering to them. Bar magnets should be kept in pairs with their poles turned in contrary directions, and they should be kept from rust. Both kinds of magnets have their power not only preserved but increased, by keeping them surrounded with a mass of dry filings of soft iron, each particle of which will re-act by its induced magnetism upon the point of the magnet to which it adheres, and maintain in that point its primitive magnetic state. ”

“ Subsequently Henry and Ten Eyk, in America, constructed some electro-magnets on a large scale. One horse-shoe magnet made by them, weighing 60 lbs., would support more than 2000 lbs.
In September 1858, there were constructed for the Atlantic-telegraph cable at Valentia two permanent magnets, from which the electric induction is obtained: each is composed of 30 horse-shoe magnets, 21⁄2 feet long and from 4 to 5 inches broad; the induction coils attached to these each contain six miles of wire, and a shock from them, if passed through the human body, would be sufficient to destroy life. ”

“ For bipolar machines the single horse-shoe (fig. 25) , which is the lineal successor of the permanent magnet employed in the first magneto-electric machines, was formerly very largely used. It takes two principal forms, according as the pole-pieces and armature are above or beneath the magnet limbs and yoke. The “over-type” form is best suited to small belt-driven dynamos, while the “under-type” is admirably adapted to be directly driven by the steam-engine, the armature shaft being immediately coupled to the crank-shaft of the engine. ”

“ Most of the magnets that we see are not real loadstone, but they are steel that has been magnetized by the loadstone. They are commonly made in a horse-shoe shape, as represented here. They will hold up a considerable weight of iron, and sometimes twenty-eight times their own weight; and it is curious that a magnet which holds a weight all the time will have its power increased. There is no tiring out of its power; and, on the contrary, [3156] if you give a magnet nothing to do, its power will grow weak—it will not be able to hold up so much weight as it did at first. ”

“ If a rod or core of soft iron c be slipped inside the coil of wire w, and insulated or electrically separated from it, so as to prevent the electric current from passing through it instead of through the wire, the core c will become a powerful magnet. As long as the electric current is passing it forms an electro-magnet. When the current ceases to flow, the iron will lose its magnetism—that is, provided it is soft. ”

“ The Human body represents three horse-shoe Magnets, two of them having the neutral point at the summit of the head and the third in an inverted position to that of the two first ones. The axis the most important divides us laterally from right to left, the other from the forepart to the back part of the body. The first horse-shoe Magnet has its neutral point at the summit of the head, and its extremities or poles at the right hand and the left hand, the right hand being the positive, and the left hand the negative pole. ”

“ It was constructed somewhat like a light diving suit or a spacesuit, but without the helmet. In the toes, knees, and hands, were powerful electromagnets controlled by switches in the fingers of the gloves and powered by the current in the long line.
Houston stepped over to the blue aluminum wall, reached out a hand, and lowered one finger. Instantly, the powerful magnet anchored his hand to the wall, held by the dense magnetic field to the steel beam beneath the aluminum sheath. That one magnet alone could support his full body weight, and he had six magnets to work with. ”

“ The softer and more homogeneous is the iron, the more instantaneously will it acquire and lose its magnetism, and the greater strength of magnetism it is able to acquire. An iron bar, round which are wound a large number of turns of insulated or covered wire, constitutes an electro-magnet. Where the magneto and dynamo machines differ. The difference then between a magneto-electric and a dynamo-electric machine is, that in the former permanent magnets are used, and in the latter electro-magnets take their place. ”

“ In the great steel works where armor plate is made powerful magnets are used to carry the hot plates from one place to another. The magnet lifts up the hot, soft metal without denting it or damaging it and drops it down where it is wanted. The power which moves trolley cars through the streets is nothing in reality but an application of the force of the magnetic principle. ——
That the earth itself is a great magnet cannot be questioned. And there is no doubt that each of us human beings is a compound magnet on his own account, depending for his welfare on magnetic force. ”

“ It has only become an instrument receptive of certain conditions, as the horse-shoe magnet has become receptive of certain magnetic conditions. We talk about the attraction of the magnet as though the attraction were in the iron. ”

“ Albertson asserts, half of the battle is won, and the world may yet be able to travel on the earth's surface with the much-dreamed-of speed [Pg 152] of hundreds of miles an hour. For many years the great principle of magnetism has been known to electricians and used in practical work by laymen. Steel companies have found the magnet useful in lifting huge metal girders. At one end of their lifting apparatuses they have placed a magnet which, when charged, grips the steel bars and lifts them, no matter how great their weight. ”

“ Thus in a shunt-wound dynamo there is a
critical resistance for the outer circuit, below which the field ceases
to be magnetized, as enough current ceases to be shunted into it to
magnetize it. The machine is said to unbuild itself, and a discharge of
magnetism occurs from the field magnet. ”

“ Now when either feeble oscillations, which have been rectified by a detector, or small currents from a B battery, flow through the magnet coils the permanent steel magnet is energized to a greater extent than when no current is flowing through it. This added magnetic energy makes the magnet attract the diaphragm more than it would do by its own force. ”