Magnets

Mina Valenzuela                O. A. Thorp Scholastic Academy
                               6024 W. Warwick Av.
                               Chicago, Il. 60634
                               312-534-3640    

Objectives:

1.  Discover how magnets work. 
2.  Demonstrate magnetic lines of force. 
3.  Find materials that can be attracted to magnets.

Materials:

  Magnets (disk, bar, horseshoe), nails, corks, erasers, paper clips, coins,
  cloth, wires, foil, paper, sticks, iron filings, compass, thread, tape, pins,
  plastic, salt, wax paper, pan, pendulum, metal sheet, bottles and container.

  
Strategy:

1.  Demonstrate to the class some magnet tricks.  

Trick #1.  Floating Disk.  Put two rings on the pencil so that the rings repel
each other.  Hold the bottom ring and move it up and down along the pencil.
What did you find out?  Try the trick with a stick, too.  The upper ring will
jump up and down as if it were attached to a spring.  The force of magnetic 
repulsion will keep the top magnet in the air.  Students may try this trick by 
pairs in their seats. 

Trick #2.  Rolling Rings.  Hold one ring between your thumb and forefinger in a
vertical position.  Hang the second ring on the first ring edge to edge.  With
a slight movement of your hand you can make the second ring travel round and
round the first ring.
                  
Trick #3.  Stand up nine nails on their heads in three rows of three nails about 
one half inch apart.  Use horseshoe magnets to remove each nail one at a time 
without disturbing any other nails.  If another nail falls or moves, it is your 
friend's turn. 

Trick #4.  Hanging Pendulum.  Tie a length of thread to two small disk magnets. 
Tie the other end of the thread to the pendulum so that the magnets hang about 
three fourths of an inch from the metal sheet.  Arrange several pieces of 
magnets on the metal sheet.  Swing the pendulum and feel the magnetic lines of 
force.  What happens?  
   
Trick #5.  Bearded Man.  Put about three pinches of iron filings on a picture. 
Slide a horseshoe or bar magnet underneath the picture.  Arrange the filing 
units into hair, eyebrows, moustache or beard.  The iron filings will stand or 
move.  Return the iron filings carefully to the bottle container. 

Trick #6.  Mix a half teaspoonful of sugar with the same quantity of iron
filings in a bottle.  Ask the audience how to separate them.  As you move the 
magnet around the bottle, the iron filings will follow but the sugar will be 
left behind.  Repeat the experiment with a salt mixture, water and glue.  

Trick #7.  Put two bar magnets side by side so that north and north pole are
facing each other.  What happens?  Repeat the procedure by putting north and
south pole facing each other.  Now what happens to the magnets?

Trick #8.  Put iron filings in a small glass pop bottle.  Using a testtube, 
glue it on the inside of the top.  Put a cow magnet inside the tube.  Shake the 
bottle and the filings will stand up and form a pattern showing the magnetic 
lines of force. 
  
2.  Predict which objects will be attracted to a magnet.  Touch your bar or 
horseshoe magnets to each of the items.  Which are attracted by and stick to the 
magnet?  Which are not attracted?  Record the results on the chart by checking 
yes or no next to each item listed.  Decide with your group what kind of 
material each item is made of.