Magnet

“ We have before said that all the motions of the magnet and iron, all its turning, its inclination, and its settlement, proceed from bodies themselves magnetical and from their common mother the earth, which is the source, the propagatrix, and the origin of all these qualities and properties. ”

“ When we place a powerful magnet near a piece of iron, say at a distance of one inch, and the magnet lifts that piece of iron by virtue of its attractive power, a contest has been waged, if one may so speak, between the attractive powers of the small magnet and of the mighty earth, and the magnet has conquered the earth. Now the [40] magnet has been much nearer than the earth to the piece of iron, for we know that the earth's attractive influence has been the same as though the entire mass of the earth were gathered at its centre, say 4000 miles from the piece of iron. ”

“ Such a magnet could not raise a single pound weight of iron two inches, and therefore could not impart motion. The magnet acts like a rock, which while at rest presses with a weight of a thousand pounds upon a basis; it is like an inclosed lake, without an outlet and without a fall. ”

“ Can you tell me what it is?"
"The magnet pulls iron," said Charlie.
"Good," said I; "and it is also true that the magnet does not pull—"
"Things that are not iron," said Charlie.
"True again," I said. "So far as our experiments go, the magnet pulls iron always, and never any thing else." ”

“ The magnet acts through media and at a distance, as well as in contact; and it has an especial attraction for iron, the more so when the conducting medium is solid, such as a table; and so when the magnet is horizontally suspended, or poised, in the vicinity of iron, its tendency to point north and south is seriously disturbed. ”

“ A magnet attracts a solid piece of iron; will a piece of a magnet dipped in a dissolution of iron attract the iron itself and so get a coating of iron? (2) Again, the magnetic needle turns to the pole; does it, in so doing, follow the same course as the heavenly bodies? (3) And, if one should turn the needle the wrong way, that is, point it to the South and hold it there for a while, and then let it go ”

“ A magnet is a piece of iron, as you might say, with a ghost in it, something sticky in its vitals. He got a chance to hold the wheel by himself. He put that magnet into the binnacle on the little shelf under the compass, on the right side of the needle, just half-way round the circle. ”

“ You have seen that the horseshoe magnet can lift nails, iron filings, etc.; you have used this lifting power to show that the magnet was really a magnet, and not merely an ordinary piece of iron painted red. Can we give some of its magnetism to another piece of steel? Can we pass the magnetism along from one piece of steel to another? ”

“ A straight magnet is called a bar magnet. Magnetize a sewing-needle. For some experiments a needle-magnet, as we may call it, is better than a large magnet.
APPARATUS 53.
72. Bar Magnet. A harness-needle, which is thicker and stronger than a sewing-needle, makes an excellent bar magnet.
APPARATUS 54.
73. Bar Magnet. For long slim magnets use a knitting-needle. Some knitting-pins, as they are sometimes called, break off short when bent, but most of them will bend considerably before breaking. These slim magnets are excellent for the study of Consequent Poles. ”

“ These effects may be produced again and again, as often as the current flows and is broken. A magnet so produced is called an electro-magnet, to distinguish it from the ordinary permanent steel magnets. By coiling the conducting wire round a bar of iron which has been bent into the form of a horse-shoe, very powerful magnets may be produced, and enormous weights may be supported by the force of the magnetic attraction so evoked. Fig. 266 represents the apparatus for experiments of this kind, in which weights exceeding a ton can be sustained. ”

“ A Magnet
"Well, is magnetism the same as electricity?"
"Both exhibit the same manifestations. Magnetism is nothing more than a body charged with electricity. The electricity, which appears to travel around the conductor (A) , extends out for some distance from its body, and produces what is called a magnetic field. This is the case whether the magnet is a permanent one, like the earth, or whether the conductor is charged by a dynamo."
"What is the difference between the north and the south pole?" ”

“ When the magnet is placed in a uniform field, the parallel forces acting on the positive poles of the constituent filaments, whether the filaments terminate outside the magnet or inside, have a resultant, equal to the sum of the forces and parallel to their direction, acting at a certain point N. The point N, which is the centre of the parallel forces, is called the north or positive pole of the magnet. ”

“ When close below, the magnet points its powers.
This experiment, seen and recorded by Lucretius, is of special interest to the student of magnetic history because of the use which is made of iron filings and also because it has led certain writers to credit the poet with a knowledge of what is known to-day by the various names of magnetic figures, magnetic curves, magnetic spectrum. ”

“ Some elements are actually repelled by a powerful magnet; these are called diamagnetic bodies. It is thought that all bodies are more or less affected by a magnet.
16. Practical Uses of Magnets. Many practical uses are made of magnets, such as the automatic picking out of small pieces of iron from grain before it is ground into flour, and the separation of iron from other metals, etc. The most important uses of magnets are in the compass and in connection with the electric current, as in machines like dynamos and motors. (See experiments with electro-magnets.) ”

“ This means that they are themselves magnets, and every magnet has a magnetic field unlimited in extent, which can almost be regarded as a part of itself. If a magnet of any size be moved, its field is moved with it, and if in any way the magnetism be increased or diminished, the field changes correspondingly. ”

“ Each magnet is accompanied by its own magnetic field. When a piece of iron is brought within the field of a magnet the lines of force passing through the iron tend to arrange the iron molecules in line or to magnetize the iron. ”

“ The following experiments are very instructive:—Suspend a magnetic needle by a silk cord, so that it will hang in a horizontal position.129 Then bring it over the centre of a large magnet lying upon a table, and it will still retain its position; but, as it is brought near to either end, it will be bent downwards, and, at the extremities, will be vertical. This experiment illustrates what is called the dip of the magnet. On the equator of the earth, the needle is horizontal, or nearly so, but as it is brought near the poles it dips, and over either magnetic pole would be vertical. ”

“ While, therefore, I claim to be the first to propose the use of the electro-magnet for telegraphic purposes, and the first to construct a telegraph on the basis of the electro-magnet, yet to Professor Henry is unquestionably due the honor of the discovery of a fact in science which proves the practicability of exciting magnetism through a long coil or at a distance, either to deflect a needle or to magnetize soft iron. ”

“ The magnet is susceptible of magnetism and the opposite virtue. The magnet and artificial electricity have, with respect to disease, properties common to a host of other agents presented to us by nature, and if the use of these has been attended by useful results, they are due to animal magnetism. ”

“ This principle appears to involve the iron as with an atmosphere, and to interpenetrate it. By one magnet we may induce magnetism in any number of iron bars without its losing any of its original force. As we have observed of the electrical forces already considered, the magnet constantly presents two points in which there is a difference manifested by the circumstance that they are always drawn with considerable power towards the north or south poles of the earth. ”

“ The ordinary phenomenon of magnetism is shown by bringing a piece of iron into the neighbourhood of a so-called magnet, where it is attracted by the latter, and if free to move will go to and cling to the magnet. ”

“ The body of the magnet passes through the aperture of the trough, one pole, say the north pole, being beneath the plane of the trough, and the other above it. As the magnet and the wire revolve about the vertical axis, the current is gradually transferred from the branch of the trough which lies in front of the magnet to that which lies behind it, so that in every complete revolution the magnet passes from one side of the current to the other. ”

“ What can show you better than such an experiment as this the magnetic attraction with which we have endowed these portions of iron? Here again is a fine illustration of this strong power of magnetism. It is a magnet of the
Fig. 53.
same sort as the one you have just seen. I am about to make the current of electricity pass through the wires which are round this iron for the purpose of showing you what powerful effects we get. Here are the poles of the magnet; and let us place on one of them this long bar of iron. You see as soon as contact is made how it rises in position (fig. 54) ”

“ Lines of force, in passing from the N to the S pole of a magnet, meet a resistance in the air, which does not carry or conduct them as easily as iron or steel. In the arrangement of Exp. 39 the lines of force are not obliged to push their way through the air, as each magnet serves as a return conductor for the lines of force of the other. [28] Either magnet may be considered an armature for the other. ”

“ Again, a magnet will induce magnetism in a piece of steel suspended nearby, though the two objects do not actually touch, each other. An object which is electrified will by induction electrify another object situated some distance away. ”

“ 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. ”

“ III. lib. ii. cap. 6, p. 243) , Albertus says: “One angle ... is to the zohron (north) ... but another angle of the magnet opposite to it attracts to the aphron (south) .” Cardan (“De Subtilitate,” Lugduni, 1663) ; Salmanazar (Book II. “of the Egyptian Hermitus, 19 stars, and 15 stones, and 15 herbs, and 15 figures”: “on one side the magnet attracts iron, on the other side repels it) ; Pietro d’ Abano (“Conciliator Differentiarum,” Mantuæ, 1472, Diff. 51, p. 104, or the 1520 Venice edition, p. 73: “know that a magnet is discovered which attracts iron on one side and repels it on the other”) . ”

“ The properties which we attribute to the particle are of the same kind as those which we observe in the complete magnet, and in assuming that the particles possess these properties, we only assert what we can prove by breaking the magnet up into small pieces, for each of these is found to be a magnet. ”

“ A magnet is conceived to be made up of elementary magnetized particles, each of which has its own north and south poles, the action of which upon other north and south poles is governed by laws mathematically identical with those of electricity. Hence the same application of the idea of lines of force can be made to this subject, and the same analogy of fluid motion can be employed to illustrate it. ”

“ Place the steel bar to be magnetized on a table, or any other convenient place, and, as nearly as possible, north and south, which position is called by philosophers, the magnetic meridian. This being done, draw over it perpendicularly a strong magnet. In this operation, it is necessary to begin at one end of the bar, and draw the magnet over its entire length, and then again in the same direction. It must not be drawn backward and forward, for the power communicated in one direction, would be destroyed by an opposite motion. ”

“ Procure small pieces of cork, wood, iron, brass, glass, lead, etc., and let pupils discover which the magnet attracts.
Have pupils interpose paper, wood, slate, glass, iron, lead, etc., in sheets between the magnet and the iron and note the effect on the force exerted.
Note that when one end of a magnet touches or comes near the end of a nail, the nail becomes a magnet, but not a permanent one. ”

“ Discussion; Bar Magnets. A piece of good steel will attract iron after merely touching a magnet. To thoroughly magnetize it, however, a mere touch is not sufficient. There are several ways of making magnets, depending upon the size, shape, and strength desired. For these experiments, the student needs only a good horseshoe magnet, or, better still, the electro-magnets described later; with these any number of small [10] magnets may be made. Straight magnets are called bar magnets.
EXPERIMENT 9. To make small magnets.
Apparatus. Fig. 3. The horseshoe magnet, H M; sewing-needles; iron filings. ”

“ Without it electricity would be a useless agent to man.
While the electro-magnet is, therefore, the formp. 19 of device which is almost wholly used, it is necessary, first, to understand the principles of the permanent magnet.
Magnetism.—The curious force exerted by a magnet is called magnetism, but its origin has never been explained. We know its manifestations only, and laws have been formulated to explain its various phases; how to make it more or less intense; how to make its pull more effective; the shape and form of the magnet and the material most useful in its construction.
Fig 5. ”

“ Magnetic storm, a disturbance in the magnetism of the earth or air, which causes the magnetic needle to move rapidly backwards and forwards.—Artificial magnet, a magnet made by rubbing with other magnets; Horse-shoe magnet, a magnet bent like a horse-shoe; Permanent magnet, a magnet that keeps its magnetism after the force which magnetised it has been removed. ”