Building Blocks of the Universe by Isaac Asimov

Author:Isaac Asimov [Asimov, Isaac]
Language: eng
Format: epub
ISBN: 9780200710992
Google: CHDhAAAAMAAJ
Amazon: 0200710990
Goodreads: 735328
Published: 2016-06-17T04:15:44+00:00

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BUILDING BLOCKS OF THE UNIVERSE

combination is called rusting. Iron unites with oxygen and water to form a hydrated iron oxide, the molecule of which contains iron atoms, oxygen atoms, and hydrogen atoms.

This is iron rust, and we are all familiar with its appearance.

Iron rust, unfortunately, is a crumbly sort of substance that flakes away from the metal. It doesn’t protect iron the way aluminum oxide protects aluminum. Instead, by flaking away, it always exposes fresh iron to the oxygen and moisture of the air. This fresh iron rusts and flakes away in its tum. Eventually the entire piece of iron rusts away.

It is for this reason that iron and most forms of steel must be painted before use. The layer of paint protects the metal from oxygen and moisture. Perhaps you have noted that steel used in construction always looks orange-red. The color is not rust, but paint.

Another peculiar property of iron is its ability to be attracted by a magnet and its ability to be a magnet.

Magnetism is a kind of energy that always occurs together with electricity ( which is another kind of energy). Any wire through which electricity is flowing behaves like a magnet; that is, the wire will attract small pieces of iron.

( Why iron is more attracted by a magnet than any other element is still something of a mystery. )

If the wire through which electricity flows is wound into a coil, the magnetism of each turning of wire reinforces that of the neighboring turnings, so that the magnetism of the coiled wire is greater than that of the same wire drawn out straight. If the wire is wound round an iron core, the iron concentrates the magnetism somehow, and a powerful electromagnet results.

The magnetism is strongest at the ends, or poles, of the iron core, and pieces of iron and steel are strongly attracted toward those ends. A big electromagnet, when

Iron

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the current is flowing through its coil, can lift tons of iron and steel. Suppose we want to load iron and steel scrap into freight cars. We do it with an electromagnet that is hung from a crane. We lower the magnet onto the scrap, turn on the current, and lift a few tons of the scrap. Then we swing the load over a freight car and turn off the current. The magnet stops being a magnet, and the scrap falls into the freight car.

Most substances are affected by magnetism in one way

or another, but usually the effects are very small. It is as if the atoms of those substances behaved like tiny magnets.

Under ordinary conditions, these atomic magnets point every which way, and their energies cancel one another out.

The presence of an electric current and the resulting magnetism, however, cause the atoms ( and iron atoms much more than any others) to line up all in the same direction.

All the little magnetisms add up to a big magnetism. When the electricity is turned off, the atomic magnets drift every which way again. Iron thus forms a temporary magnet.

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