Day 5: Interpreting Magnetic Field Maps
Students will be able to:
(a) Interpret magnetic field maps.
(b) Rotate the coordinates to obtain different views.
(c) Change the coordinate representation.
(d) Produce alternate graphical representations.
- 2 bar magnets
- 4-6 ring magnets (large diameter if available)
- 2 cups
- Graph paper
Assigned homework was to draw the field lines for 5 different
arrangements of pairs of dipole magnets. The essential features are
that lines go between opposite poles, field lines always start on one
pole and end on the other, field lines have definite direction, and field
lines do not cross. Students will be asked to explain their predicted maps
and differences from actual observations.
Ask students to test one of their homework predictions. If possible,
have all 5 combinations tested by at least 2 groups. Ask each group to
report out results, including how the earth's magnetic field has hampered
the measurements. This could be used as a graded exercise as it requires
application of the previous class activity and compares a prediction with
an actual observation.
Students will map the field of a stack of ring magnets. First map the
field of the stack while the stack is lying on its side, forming a tunnel,
if you will. Second, map the stack on end, forming a well, if you will.
Questions: The same magnets produced each of the mapped fields. What is
different? Are the two maps representations of the same thing? If so,
how is the thing changed between representations? Where both of the
representations present in each of the mapping exercises? Could you have
turned something else on its side to get the two different maps?
Students will look at a map of the field near the end of a single
dipole magnet. Students will make a plot of how the magnetic field would
appear to a magnetic particle that was moving through the field perpendicular
to the long axis of the bar magnet, but in the plane of the bar magnet as shown.
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The desired graph will show magnetic field strength on the vertical axis
and distance traveled on the horizontal axis. The expected graph is as
Repeat the exercise but let the magnetic particle move in the plane of
the magnet parallel to the long axis of the magnet. The same axis will be
used but this time the field will show variation in sign and in strength.
The expected graph will resemble the following.
Construct a way of making a magnetic field that had only straight field lines.
Lesson Development/Writing: Ed Eckel
Web Design: Theresa Valentine
Last Updated: 8/24/2000