EXPERIMENT 6. To ascertain the nature of substances attracted by a magnet.
Apparatus. The horseshoe magnet, H M ([Fig. 2]); silver, copper, and nickel coins; iron filings (No. 17), nails, tacks, pins, needles; pieces of brass, lead, copper, tin, etc. (Ordinary tin is really sheet iron covered with tin.) Use the various battery plates for the different metals.
14. Directions. (A) Try the effect of H M upon the above substances, and upon any other substances thought of.
15. Magnetic Bodies; Diamagnetic Bodies. Substances which are attracted by a magnet are said to be magnetic. A piece of soft iron wire is magnetic, although not a magnet. Very strong magnets show that nickel, oxygen, and a few other substances not containing iron, are also magnetic. 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.)
EXPERIMENT 7. To study the action of magnetism through various substances.
Apparatus. Horseshoe magnet, H M; a sheet of stiff paper; pieces of sheet glass, iron, zinc, copper, lead, thin wood, etc.; sewing-needle. (A tin box may be used for the iron, and battery plates for the other metals.)
17. Directions. (A) Place the needle upon the paper and move H M about immediately under it.
(B) In place of the paper, try wood, glass, etc.