Activity 3 Overview
Youngsters will create their own paper cup speaker and hook it up to
a small radio.
Estimated Time and Age Level
Advance Preparation: 20 minutes
Activity: One 50-minute session
(Ages 11-14)
Materials
(Per Team)
1 paper cup (4 oz. to 10 oz.)
1 small bar magnet (approx. 1
or 2 cm. wide and at least 3 cm. long; a bar-shaped stack of tiny magnets
will also work)
masking tape
2 ice cream sticks
3-by-5-inch index card
scissors
wire stripper (if available)
6 meters (20 feet) of thin enameled
wire
emery paper, 220 grit or finer
(optional)
(For the whole group)
At least 1 small transistor radio
with AM reception
At least 1 monaural transistor
radio ear plug (generally available from Radio Shack® or other electronics
supply stores for about $2)
Preparation
Cut about 3 meters (10 feet) of
thin enameled wire for each group. Using the scissors or the wire stripper
(if one is available), scrape about 1 centimeter of coating off of the
tips of each length of wire. If you want, ask youngsters to help by using
emery paper to clean the ends of the wire (as well as assisting with the
other Preparation steps).
To enable youngsters to hook up
their speakers to the radio, you'll need to prepare a simple wire "jack"
or connector using the monaural ear plug. Use scissors to cut the cord
at the end near the ear plug. Discard the ear plug. Using the scissors
or wire stripper, if you have one, carefully strip away two centimeters
of plastic coating from the cut end. (Note: if an ear plug of this sort
is not available, you can substitute an inexpensive pair of personal stereo
headphones. You'll have to separate the wires and pull back the loose strands
of copper wire you'll find beneath the outer plastic coating. You won't
be needing them. Then carefully strip two centimeters of coating off of
the remaining wire and your "jack" is complete.) Make one jack
for each radio. The more radios you can collect, the less waiting each
team will have to do.
Set up at least one radio to use
for this activity. The best kind would be a small transistor radio that
has a speaker and a headphone jack. You could substitute a personal radio
that uses only headphones, but since such radios use very little power,
youngsters will need to make their speakers very well to get them to work.
Do not use an expensive stereo system. Large amplifiers can be damaged
by paper cup speakers. However, any radio that has a compartment for batteries
will work fine.
Print out 1 copy of the Speaker-in-a-Jiffy
directions for each team.
Set out the materials in a central
location.
Procedure
Set the stage for the activity
by asking youngsters to reprise lessons learned from the String
It Along activity. Discuss how real telephones have small speakers
inside them that change electricity into the sound vibrations that we all
hear when talking with our friends. To discover exactly how these speakers
work, youngsters are now going to make their own "Speaker-in-a-Jiffy"
Hand out the prints of the
Step-by-Step
box. If necessary, help youngsters assemble their speakers. Younger children
might have trouble making neat coils, and that is critically important.
To help them with this step, suggest that they keep wrapping the wire about
ten times around the tube, and then pushing the coil down to one end. They'll
find it easier to keep the coil neat if they keep pressure on the wire
the entire time they're wrapping it.
After youngsters complete their
speakers and (taking turns) hook them up to the radio, they should be able
to clearly--if somewhat faintly--hear radio signals coming through their
speakers. If they don't, have them make sure the magnet is attached to
the bottom of the cup and can move freely within the coil. They can also
try pushing the ice cream sticks apart to immobilize the coil.
Challenge youngsters to relate
what they've just seen (and heard) with what they discovered about sound
vibrations in Activities 1
and 2.
What is vibrating in the cup that produces sound? What's making it vibrate?
They may be able to guess that the magnet is vibrating because it has been
stimulated in some way by the radio. (In short: the radio's electric current
is generating its own magnetic field, which repels and attracts the magnet--i.e.,
makes it vibrate. The magnet taps the bottom of the cup and makes it vibrate
as well, pushing the air on the other side in and out in the same pattern
as the one the original sound wave produced at the radio station. See Unit
4 for more information.)
This activity has been copied, with permission, from the National Science Foundation server to ours, to allow faster access from our Web site. We encourage you to explore the original site.