Magnetism
Is there any connection between magnetism and electricity?
There is every reason to believe that magnetism and electricity are but modifications of one force.
What is a loadstone or a natural magnet?
It is an ore of iron, known as the “protoxide of iron,” or “magnetic oxide of iron,” which is capable of attracting other pieces of iron to itself; and if suspended freely by a thread, and left to take its own position, it will arrange itself so that its extremities will point towards the north and south poles of the earth.
Are natural magnets rare?
They are not; they are found in many places in the United States. In Arkansas, especially, an ore of iron possessing remarkably strong attractive powers is very abundant.
The magnetic ore is usually of a dark gray hue, and possesses but little metallic luster. If a piece of this ore be dipped in iron filings, or a number of small needles, they will generally be found collected and clinging together in great quantities at two opposite extremities, whilst the middle portion is nearly destitute. The magnetic property, whatever it may be, seems therefore to be collected and act with the greatest energy at two opposite extremes; these have been termed poles.
What is the origin of the terms “magnet” and “magnetism”?
The loadstone or natural magnet was first found at Magnesia, in Lydia, Asia, whence were derived the names.
Can a natural magnet communicate its attractive properties to other bodies by contact?
It can, and that too without any apparent loss of attractive strength.
What bodies are capable of being magnetized by contact with natural magnets?
Iron and steel are the substances most susceptible of this influence, but brass, nickel, and cobalt can also become magnets.
Does the magnetism imparted to a piece of soft iron, or steel, by contact with a natural magnet, remain permanent in their substances?
In the steel it does, but the soft iron loses its power as soon as it is removed from the magnet.
Is it necessary that absolute contact should take place between a magnet and a piece of soft iron to render the latter a magnet?
No, every piece of soft iron brought near a magnet becomes by induction itself a magnet.
What do you mean by induction?
It is the production of like effects in contiguous bodies. In electricity or magnetism, it is the influence exerted by an electrified or magnetized body through a non-conducting medium without any apparent communication of a current.
What is meant by the directive power of the magnet?
It is that power which will cause a magnet, when suspended freely, to constantly turn the same part towards the north pole and the opposite part towards the south pole of the earth.
What are the poles of a magnet?
They are the ends of the magnet, and are denominated north and south, according as they point to the north or south poles of the earth.
What are the poles of the earth?
The extremities of the earth’s axis, or the points on the surface of the globe through which the axis passes.
What is a magnetic needle?
Simply a bar of steel which is a magnet, suspended in such a way that it can freely turn to the north or south.
What is a mariner’s compass?
It is a delicate steel bar or needle balanced upon a pivot placed beneath its center of gravity in such a way that it can turn horizontally without obstruction. This needle is usually inclosed in a box, upon the bottom of which is a card, with the various points—north, south, east, west, etc., etc., marked upon it.
Such a needle, if the box containing it be placed on a level surface, will generally be observed to vibrate more or less, till it settles in such a direction that one of its extremities or poles will point towards the north, and the other consequently towards the south. If the position of the box be altered or reversed, the needle will always turn and vibrate again, till its poles have attained the same direction as before.
Does the compass needle always point exactly north and south?
It does not; its natural direction is towards the north and south poles, but it seldom points due north or south.
Who first discovered the fact that a magnet would invariably point to the north and the south, and made use of this knowledge in constructing a compass?
It is claimed to have been discovered by the Chinese: it was known in Europe, and used in the Mediterranean, in the thirteenth century.
How were the compasses of that time constructed?
They were merely pieces of loadstone fixed to a cork, which floated on the surface of water.
Is the earth itself supposed to be a magnet?
It is undoubtedly a great magnet.
Is iron under certain circumstances rendered magnetic by the inductive action of the earth’s magnetism?
Most iron bars and rails, as the vertical bars of windows, that have stood for a considerable time in a perpendicular position, will be found to be magnetic.
If we suspend a bar of soft iron sufficiently long in the air, will it assume magnetic properties?
It will gradually become magnetic; and although when it is first suspended it points indifferently in any direction, it will at last point north and south.
How may a bar of iron, such as a kitchen poker, be made immediately magnetic, without resorting to the use of other magnets?
If the bar devoid of magnetism is placed with one end on the ground, slightly inclined towards the north, and then struck one smart blow with a hammer upon the upper end, it will immediately acquire polarity, and exhibit the attractive and repellant properties of a magnet.
What is a horseshoe magnet?
It is a magnetic bar bent into the form of a horseshoe.
When a piece of iron not magnetic is brought in contact with a common magnet, it will be attracted by either pole; but the most powerful attraction takes place when both poles can be applied to the surface of the piece of iron at once. The magnetic bars are for this purpose bent into the shape of the letter U, and are termed horseshoe magnets. Several of these are frequently joined together with their similar poles in contact; they then constitute a magnetic battery, and are very powerful, either for lifting weights, or charging other magnets.
If we break a magnet across the middle, what happens?
Each fragment becomes converted into a perfect magnet; the part which originally had a north pole acquires a south pole at the fractured end, and the part which originally had a south pole, gets a north pole.
If we divide a magnet to the extreme degree of mechanical fineness possible, will the pieces possess magnetic powers?
Each fragment, however small, will be a perfect magnet.