THE MAGNETIC FIELD 



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takes a north and south direction, the pole pointing north 

 being called the north pole, and the pole pointing south, 

 the south pole. If we bring the north pole of one magnet 

 near the north end of a suspended magnet, the north pole 

 moves away. If we bring the south pole of a fixed magnet 

 to the north pole of a movable one, the south pole is drawn 

 toward the north. These curious facts are always noticed 

 when two magnets are brought together, and from this we 

 are able to state the law, which is as follows : Like mag- 

 netic poles always repel, and unlike magnetic poles always 

 attract, each other. 



The magnetic field. It is not necessary to touch a small 

 piece of iron such as a tack in order to attract it. You 

 have often noticed tacks 

 or bits of iron jump 

 across the air space to a 

 strong magnet. A com- 

 pass needle will turn 

 when several feet away 

 from a strong magnet. 

 These facts indicate that 

 the influence of the mag- 

 net extends in all direc- 

 tions. This force de- 

 creases as the distance 

 increases. The space about a magnet in which magnetic 

 influence exists is called the magnetic field. It is because 

 the earth itself is a huge magnet and has surrounding it 

 a magnetic field, that the compass needle takes a definite 

 direction. Every magnetic field is filled with magnetic 

 lines of force which are imaginary lines denoting the direc- 

 tion of the magnetic force. 



A magnetic field. Iron filings scattered over a 

 magnet arrange themselves in the lines 

 shown. 



