Man's physical universe

xanabras

MAGNETISM 479

Magnets Are Surrounded by Magnetic Fields.

The fact that it is not necessary for magnets to touch each other in

order for their attractive or repulsive force to act is accounted for by the

hypothesis that the space around a magnet must be in a state of strain.

Fig. 224. A floating magnet. One magnet is held in position above the other

magnet, because of the repulsion of like poles.

The region subject to this strain is called the magnet's field, or simply

the magnetic field.

A very good map of such a field can be obtained by

placing a piece of paper over a magnet and then sprinkling iron filings

over the paper; see Fig. 225. It will

be noted that the complete lines of

force (used to represent a magnetic

field) extend from the north pole to

the south pole or vice versa, and this

would be found true of every line if

one could follow it far enough, as indicated

in Fig. 226.

Michael Faraday (1791-1867), the Fig. 225. Lines of force of a rod

experimenter who did more than any magnet as shown by iron filings

other man to place the science of P'^^^^ o" ^ ^^^^^ of P^P^'' ^^^^^

magnetism and electricity upon a firm ^ ^

basis, found that these lines of force behave like stretched rubber

bands, trying to shorten in the direction of their length and to widen in

the direction of their width.

The Earth Is a Giant Magnet.

The poles of an ordinary magnet derive their names from their

behavior toward the earth. Those that point north are called north

poles. As we have already pointed out, the magnetic poles and geographic

poles do not coincide.

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