MATERIALS AND WORKSHEETS:
- 1 paper grocery bag made from recycled materials (these bags will
break down the best)
- one plastic grocery bag (optional)
- 1 dead D-size battery
- 2 ceramic donut magnets, 1 and 1/8 inch in diameter
- masking tape
- 3 rubber bands (size 64 will work best)
- marker or thick pen
- magnetometer instrument (see Magnetometer
Activity for instructions
about building a simple, inexpensive magnetometer)
Worksheets:
 DIRECTIONS:
Overview: Students will build a simulated planet with
a magnetic core. The core will consist of a battery with "donut" magnets
taped onto the ends, creating the equivalent of a larger bar magnet.
The core will be wrapped in a crumpled paper bag (the bulk of the "planet").
The bag will be held shut by rubber bands, which will also serve as latitude
and longitude lines dividing the "planet" into eight segments. The students
will use a magnetometer to determine which octant of the planet the north
and south magnet poles are beneath. They will record this info, then
swap planets with other groups so they can repeat the "finding the poles"
process on several different "planets".
Refer to our Terrabagga
photos page to see pictures of the stages of this procedure.
- You may wish to demonstrate the process of building a "planet" and
finding the orientation of its magnetic field to your students first,
and then having them do the process themselves.
- The first step in building
a "planet" with a magnetic field
in it is to create
the
dipolar
magnet
that
will
go
inside
the
world.
Take
the
two magnets and place them on top of each other so that the magnets
are attracted to each other. Now without flipping either magnet over,
place the top magnet on the top of the battery. Tape this magnet
in place. Place the bottom magnet on the bottom of the battery (remember,
the side that was facing up, should now be against the casing of
the
battery). Tape this magnet in place.
- Next turn the paper bag inside out. This creates
a clean surface that will be labeled later on. Work the bag by crumpling
it and folding it.
- When the bag is turned inside out and is pretty workable, place your
battery (with the magnets taped on) inside the paper bag. It does not
matter which way the battery is facing. Work the paper bag around the
battery to create a nice smooth (fairly round) world. Try to center the
battery/magnet in the middle of the "planet". If one pole is too close
to the surface, the opposite pole may be buried too deeply to sense
with the magnetometer. You may wish to use the optional plastic bag
to add extra padding to the "planet's" interior to help center the
magnetic core, or you may want to "double-bag" the "core" to accomplish
the same result (i.e. first wrap the plastic bag around the "core",
then surround both with the paper bag).
- Now it's time to put the rubber band markers on your world. The first
rubber band can just be placed wherever it's most needed to hold your
world together. Just stretch the rubber band around your world.
- Now stretch one more rubber band across your world. This rubber band
should meet at right angles with the first rubber band so that your
world is now split into 4 equal segments. Pick one of the intersections
of your two rubber bands to be the geographic north pole. Make sure
the north pole is facing up.
- Now it's time to label parts of your world. Note that the rubber
bands make a "X" when looking down on the north pole. The
four "branches" represent four lines of longitude separated by 90°;
the prime meridian at 0°, 90° west longitude, the international
dateline at 180°, and 270° west longitude (which is the same
as 90 east longitude). Pick one of the two rubber bands to label first
(either one - it doesn't matter which you do first). Use the marker
to write a zero on the rubber band on one side of the North Pole, then
write "180" on the same rubber band on the opposite side of the North
Pole.
- Now turn your world so that you are looking at the prime meridian
(the line of zero longitude) with the "North Pole" up. Everything east
(right) of the prime meridian all the way to the international
dateline is the eastern hemisphere. Everything west (left) of the prime
meridian all the way to the international dateline is the western hemisphere.
Label the part of your (unlabelled) rubber band that lies in the eastern
hemisphere 90 E, because it represents the longitude of 90 degrees
east. Label the part of that same rubber band that lies in the western
hemisphere, 90 W, because it represents the longitude of 90 degrees
west.
- Next add the third rubber band to your world. This rubber
band should stretch across both of the other rubber bands meeting those
rubber bands at right angles. This rubber band is your world's
equator, so it should be stretching across the middle of your world.
Once that rubber band is in place, label that rubber band "equator".
Everything above equator towards the geographic north pole is the northern
hemisphere and everything to the south of the equator is the southern
hemisphere. Your world should now have eight equal segments.
- It's time to label the 8 segments. The segments in the northern hemisphere
should be labeled 1-4 with segment 1 being between 0 and 90 E. Segment
2 is then between 90 E and 180, segment 3 is between 180 and 90 W and
segment 4 should end up being between 90 W and 0. The segments in the
southern hemisphere should be labeled 5-8 with segment 5 being below
segment 1 and so on so that segment 8 is below segment 4.
- Have students make up a name for their "planets". Have them write
the "planet's" name on the "planet" somewhere (at the geographic south
pole would
be good).
- Students should use their magnetometer to test where the
magnetic north pole of their world is. The magnetometer end labeled
north should
dramatically
point in where the magnetic north pole of their world is. Have the
students write the segment number where they find the magnetic north
pole of their world onto their student worksheet. Have them follow
a similar process to locate the magnetic south pole of their "planet".
- Have student groups trade planets. Students should use their magnetometers
to locate the north and south magnetic poles for several planets and
record that information on their student worksheets.
ASSESSMENT:
- Check to see whether students correctly labeled the rubber bands representing
longitudinal meridians and the equator to assess their understanding
of these geographic concepts.
- Check whether students understand that magnets have opposite north
and south poles. See if the students correctly labeled the poles on
the "planet" they created.
- Check whether students correctly used their magnetometers to find the
north and south magnetic poles of the other worlds they explored (the
ones created by other student groups).
BACKGROUND INFORMATION:
This activity requires use of a magnetometer. See the Magnetometer Activity link in the "Related activities" section below for instructions about building a simple, inexpensive magnetometer.
Have students work in groups of 2-3 for this activity.
The instructions to students for this activity are written at a level that may not be suitable for younger students. If you teach elementary-aged students, you may need to revise the instructions or provide them verbally to your students. Also, teachers of younger students may wish to revise this activity by building the Terrabaggas for the students and simply having the students test the pre-assembled planets to determine the directions of their magnetic fields.
The dead D-size batteries in this lesson are used for their steel casing.
Most recycling centers that have battery recycling will gladly let you take
a bagful of dead D batteries home with you for free. The battery with the
donut magnets taped on create the "bar magnet" found in the core
of many of the planets and moons. The donut magnets used for this activity
can be found at Radio Shack stores across the nation. These magnets have
a definite north and south pole - with the top face of the magnet being
one polarity and the bottom face of the magnet being the opposite polarity.!
This activity brings up many interesting points of discussion. You may
choose to discuss with your students lines of longitude and lines of latitude.
You may choose to discuss why geographic and magnetic poles don't always
line up. Or you may choose to discuss what a magnetic field around a planet
or moon tells us (magnetic fields point to convection of molten material
in a body's interior and this in turn could mean the body has tectonic activity
or volcanic activity). It is at least important for the students to know
that most planetary space missions carry magnetometer instruments. The magnetometer
instrument the students built and used is just a simplification of the magnetometer
instruments that get launched into space onboard spacecraft headed to Mars,
Jupiter and beyond!
RELATED SECTIONS OF THE WINDOWS TO THE UNIVERSE WEBSITE:
Related activities:
References & Background Information:
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