XIV. MAGNETISM AND ELECTRICITY 



ELECTROMAGNETS 



1. Bring first one end of a bar magnet and then the other 

 to the north pole of a compass needle. Try the south pole 

 of the needle in like manner. State what appears true of the 

 effect upon each other (a) of like poles ; (b) of unlike poles. 



2. Compare the number of small nails that one 7 pole of a 

 bar magnet will support with the number that can be picked 

 up (a) when the like poles of two bar magnets are used 

 together ; (6) when their unlike poles are together. 



3. Put a bar magnet across one pan of a balance, and 

 counterpoise it. Bring close above its north pole the south 

 pole of another bar magnet, and state the results. What is 

 all the time true of the weight of the magnet ? Account for 

 what occurred. 



Bring the balance into equilibrium. Repeat the test, 

 bringing like poles together. Explain the result. 



4. Observe closely as the teacher connects a "dry cell" 

 to the ends of the coil of an electromagnet, and tests the 

 effect of the magnet upon nails. 



Determine by trial which is the north pole of the electro- 

 magnet while connected with the cell. Mark this pole N. 

 Then connect the coil with the cell so that the current is sent 

 through the coil in the opposite direction, and test the 

 polarity anew. State all the results. 



5. Note about how many nails the electromagnet supports 

 when the current is passing through the coil. As carefully 



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