LESSON 2: What is a magnetic field?

AIMS:

1.  What is a magnetic field?

2.  What is a compass?

3.  How do we make and use a compass?

MOTIVATION:

When the children experimented with their magnets, they should have noticed that the magnet attracted iron objects even without touching it.  Explain that a magnetic field exists around all magnets.  Show examples to the class.  You can even measure the distances of the magnetic field around the magnets.  Do all magnets have the same size magnetic field?

PROCEDURE:

1.  Have students research what a magnetic field is by logging on to the following web sites:

http://brainpop.com/science/forces/magnetism/index.weml

The following are some pictures of magnetic fields taken from those websites:

2.  Have the students perform the following experiment to see the magnetic field around different magnets.

 Problem:  How can we show a magnetic field? Hypothesis:  I think if I sprinkle iron filings around a magnet, then I will be able to see the magnetic field. Materials:  white paper, magnets of different sizes and shapes, iron filings Procedure:  1.  Place each magnet, one at a time, under the sheet of white paper.   2.  Sprinkle iron filings over the surface of the white paper, near the magnet.  3.  Tap the paper slightly, and observe where the iron filings line up.  4.  This is the magnet's magnetic field.  5.  Draw a picture of the magnetic field. Observations:  (See student samples). Conclusion:  I learned that it is possible to see the magnetic field surrounding a magnet by sprinkling iron filings over the magnet.  I also learned that different shaped magnets have different shaped magnetic fields.

3.  From the children's research, they have learned that the Earth is a giant magnet.  They will use this information to learn what a compass is, how it works, and how they can make their own compass.

A.  Students are to log on to

http://www-istp.gsfc.nasa.gov/Education/Imagnet.html

http://school-for-champions.com/science/magnetism.htm

http://home.interserv.com/~skyblade/compass.htm and research what a compass is.  The following pictures are some examples of compasses:

B.  Hand out compasses to each student or pair of students.  Have them hold the compass in the palm of their hand.  Notice which way the painted end of the needle is facing.  Explain that that direction is North and they should slowly turn their compass so that the N is in line with the painted end of the needle.  Let the children label North in the classroom.  Have each group of students find East, West, and South and label those as well. Ask questions like:

1.  How do we know where North is?

2.  How were we able to find the other directions?

3.  How can we use a compass to find directions anywhere?

4.  Have students make their own compass.  From their research, they have learned that a piece of iron can be magnetized by rubbing it on a magnet.  Do the following experiment:  (For a printable student copy, click here).  To see student samples, click here.

 Problem:  How can we make our own compass? Hypothesis:  I think if I rub an iron needle in one direction only about 20 times, then I can magnetize the needle. Materials:  magnet, iron needle, paper clip, water, cork or aluminum foil, marker, and non-iron bowl. Procedure:  1.  Hold your magnet in one hand, and stroke the needle over the magnet about 20-30 times in one direction only!  2.  Make sure your needle is magnetized by attracting to a paper clip as a test.  3.  Place your needle next to the magnet's North end.  If it attracts, you know that end of the needle is South.  Mark the North end of the needle with the marker.  4.  Place the needle on the cork or aluminum foil, and float in the water.  5.  Watch what happens to the needle. Observations:  What happened to the needle when floated in the water?  How did you make a compass?  Can you tell which direction is South?  East?  West? Conclusion:  I learned that a magnetized needle can be used as a compass to tell direction.

 Follow up Activities: 1.  Have students research the history of compasses.  Who first discovered their use?  How were they used?  Good site to explore-http://sciencetech.technomuses.ca/english/schoolzone/Info_Magnets.cfm#temp 2.  Have students make their own compass at home and find North, South, East, and West at their home. 3.  For advanced students and older children, have them research the relationship between sunspots, the Earth's magnetic field, and the Aurora Borealis.

 OVERVIEW ASSESSMENTS RUBRIC STUDENT SAMPLES

 What is magnetism? What is a magnetic field? LESSON 3 What is electricity? What is an electromagnet?