SOME WAYS OF PRODUCING ELECTRICITY 173 



Magnets made of (1) keep their strength much longer than 



those made of (2) iron. A knife blade can be (3) by 



stroking each half from the (4) with the (5) ends of a 



strong magnet. Every magnet is (6) by a magnetic (7) 



which is filled with (8) of magnetic (9) Like magnetic 



(10) (11) but unlike (12) poles (13) each other. 



The needle of the magnetic compass takes the direction of the 



(14) lines of (15) of the (16) Magnetism (17) 



through (18) which are (19) , such as glass, copper, and 



wood. A magnet will attract only (20) substances. 



STORY TEST 



RALPH GIVES His OBSERVATIONS ON MAGNETS 

 Read carefully and critically. List all the errors and suggest corrections. 



They make very powerful magnets out of an alloy of steel, nickel, 

 and cobalt. Nickel is not a magnetic substance because when I 

 tried to lift a 5^ piece with a magnet it was not attracted. I saw 

 two of these powerful magnets demonstrated. When the two 

 magnets were laid on the table with unlike poles together and 

 released they pushed apart because like poles repel. One magnet 

 would hold the other in the air above it when guides were placed 

 so that the top magnet could move only vertically and the north 

 pole of one was placed on the south pole of the other. The mag- 

 netic field was so strong that when a compass was placed 8 inches 

 away from the middle of the magnet the needle took a position parallel 

 to the magnet with its poles pointing in the same direction as those 

 of the magnet. When one end of a bar of copper was placed in 

 iron filings and the upper end of the copper touched with the magnet 

 the copper became a temporary magnet and when lifted iron filings 

 clung to it. I saw a magnet held horizontally, lowered into a pan 

 of iron filings and lifted. The largest mass of iron filings was near 

 the middle of the magnet because that is the place where the 

 magnetic force is concentrated. If a magnet is cut in two at its 

 center, the lines of force within the magnet will be cut off and all 

 the magnetism destroyed. 



PROBLEM II. WHAT ARE SOME WAYS OF PRODUCING 

 ELECTRICITY? 



You have sometimes made an electric spark when you 

 " scuffed" your feet over the carpet in winter or rubbed 

 the cat's fur the wrong way, or when your hair stood up 



