Fig. 3.—A Horseshoe Magnet
Stroke a large darning-needle from end to end, always in the same direction, with one end of a bar magnet. Then dip the needle in some iron filings and it will be found that the filings will cling to the needle. The needle has become a magnet.
Dip the bar magnet in some iron filings and it will be noticed that the filings cling to the magnet in irregular tufts near the ends, with few if any near the middle.
Fig. 4.—A Magnetized Needle and a Bar Magnet which have been dipped in Iron Filings.
This experiment shows that the attractive power of a magnet exists in two opposite places. These are called the poles.
There exists between magnets and bits of iron and steel a peculiar unseen force which can exert itself across space.
The power with which a magnet attracts or repels another magnet or attracts bits of iron and steel is called
Magnetic Force. The force exerted by a magnet upon a bit of iron is not the same at all distances. The force is stronger when the magnet is near the iron and weaker when it is farther away.