Download Magnet Lab - Warren County Schools

LAB – Introduction to Magnetic Fields
What Is a Magnet?
A magnet is a solid object, usually a rock or piece of metal, that can push or pull objects made of
iron. Go on a magnet hunt around your house to find out what types of objects are magnetic. Look
around and make of a list of objects you see that you think will be attracted to a magnet and another
list of objects you think won't be attracted. Test each object you wrote down by holding them close
to a magnet, such as a horseshoe or bar magnet. (Note: Never use magnets on or near computers,
cassette tapes, discs, or other electronic devices because it could damage the magnets inside of
them!) Mark the items on your lists that stick to the magnet. Compare your results (the items that
were and weren't magnetic) with your predictions (the lists you made at the beginning).
A magnetic field is a kind of aura that surrounds magnets. Although it can’t be seen directly, the
overall shape can be seen by the effect it has on iron filings. The invisible area around a magnet
that attracts other objects is called a magnetic field. Magnetic objects (such as paperclips) will get
pulled toward the magnet if they are placed in this field. Because iron filings are tiny and each one
is highly attracted to magnets (in other words, they are magnetic), they quickly "jump" into position
in the pattern of the magnet's magnetic field. Anything that is not magnetic, such as the paper and
the plastic bag, is not affected either. A magnetic field is strongest at the magnet's poles (the ends of
a bar magnet). Each pole of a bar magnet has a different charge. You can see this by the different
colors and the markings on the end: "S" for south and "N" for north. In magnets, opposite charges
are attracted to each other while charges that are the same repel or push away from each other. You
can test this by holding the ends of two bar magnets together - when you hold the ends marked "N"
(the magnets' north poles) toward each other, you should be able to feel the magnets pushing away
from each other. Flip one magnet over so that its south pole (marked "S") is toward the other
magnet's north pole and notice how the magnets pull toward each other.
Did you know that the earth also has a magnetic field? In fact, Earth's magnetic field is quite large.
Scientists think it is caused by Earth's core, which is made of molten (very hot, melted) iron, the
same element you used to see the field lines of the magnet in the project above. Earth's magnetic
field is important because it blocks wind caused by the sun and harmful radiation from space from
reaching us on Earth.
Fun Facts
• A neutron star (what is left after a star collapses) has the strongest magnetic field of any object in
the Universe!
• In the 1800s, two important scientists, named Michael Faraday and James Clerk Maxwell, made
great discoveries in their studies of electromagnetism.
• Make a temporary magnet by straightening a paperclip and rubbing a bar magnet across it in
only one direction (not back and forth). Try using it to pick up other paperclips.
Problem:
How can I see a magnetic field?
Materials:
 Bar magnets (2)
 Iron filings
 Sheet of 11 x 14” white paper
Procedure:
1. Place a bar magnet on a horizontal surface. Cover the magnet with a sheet of paper,
ensuring that the magnet is under the center. Carefully sprinkle iron filings on top of the
paper. Jiggle the paper slightly to help the iron filings move their way into the magnetic
field pattern. PICK UP PAPER AND POUR THE FILINGS BACK IN BOWL!! CAN’T GET NEAR
MAGNETS.
Sketch the pattern of the magnetic field below (FIGURE 1)
2. Arrange two bar magnets in a line with opposite poles facing each other. Leave about one
inch (2.5 cm) between the poles. Use the iron filings to see the magnetic field as before. DO
NOT LET THE IRON FILINGS NEAR MAGNETS. PICK UP PAPER AND POUR THE FILINGS
BACK IN BOWL!! CAN’T GET NEAR MAGNETS.
Sketch the pattern of the magnetic field below. (FIGURE 2)
N
S
3.
3.. Arrange two bar magnets in a line with north poles facing each other. Leave about an inch
between the poles. Use the iron filings to reveal the magnetic field as before. PICK UP PAPER
AND POUR THE FILINGS BACK IN BOWL!! CAN’T GET NEAR MAGNETS.
Sketch the pattern of the magnetic field below. (FIGURE 3)
N
N
Conclusion Questions:
1. A magnetic field is strongest where it ha the most lines of force. Where is the field strongest
around the magnet?
2. How do the sketches of Figure 1 and Figure 4 compare?
3. Sketch the pattern for the magnetic field for the following:
a.
S
S
b.
N
SS
S
N
S
Does this pattern show attraction or repulsion field lines? [Circle one]
c.
N
S
S
N
N
Does this pattern show attraction or repulsion field lines? [Circle one]