MAGNETS 43 



EXERCISE 42 

 MAGNETS 



Apparatus and Materials. Bar magnet and horseshoe magnet, 

 small iron nails or tacks, iron filings, sewing needles, cork, dish of 

 water (glass or porcelain), iron "cut" nail or a wire nail, sheet of paper 

 or a pane of glass. 



a. Bring one end of a bar magnet or horseshoe magnet near 

 some iron nails or tacks; near a needle, a pin, a piece of "tin- 

 ware," a piece of copper (a cent). Are all attracted? Try the 

 other "pole" of the magnet with the same materials; what are 

 the results? 



b. Magnetize a needle by stroking it, from the middle to the 

 point, with one end of a magnet. Magnetize a second needle 

 by stroking it with the other end of the magnet, also from the 

 center to the point. 



Cut two thin, circular slices of cork from a small cork stopper, 

 and push each needle through one of the slices, so that the cork 

 will make the needle float in a horizontal position. Float the 

 two magnetized needles on some water in a porcelain or glass 

 dish (not an iron one). 



Find out whether the points of the two needles attract or 

 repel each other. The eye ends. The eye end of one and the 

 point of another. 



Float a third needle, one that has not been magnetized at 

 all, near one of your floating magnets. Does it show repulsion 

 for either end of the magnetized needle? 



c. Hold one end of your large magnet over the floating mag- 

 net, and account for the movements that take place. From 

 the position which the floating magnet takes, and from the way 

 in which it acts toward your large magnet, decide which end of 

 the large magnet is north-seeking. 



d. Hold a nail near one end of a magnet, as in Fig. 113 of the 



