Now that your students have been exposed to some basic magnetic principles, they are ready to begin working with static electricity. Then with knowledge of static electricity along with understanding magnets, we will begin our investigation of simple electronics.
Activity #1: Balloon experiments
This is a good opening activity to try with your class. Take an inflated balloon and rub it on a wool carpet. Then hold the balloon above your head. Your hair should stand on end. The charged balloon attracts your hair.
Now, take two inflated balloons and tie a string between them. Rub each balloon on a wool carpet or sweater to charge the balloons. Let the balloons hang next to each other, they should repel. (Science for Fun, p117).
How it works: Just as magnets repel when like charges are next to each other. Static electricity works the same way. Since both balloons were rubbed on the same material, they were given the same charge, therefore they repel. (Science for Fun, p117).
Activity #2: Comb experiments
You will need a plastic comb, a wool carpet, coat or sweater and some small ripped up scraps of paper about the size of a ½ dollar. You will first rub the plastic comb on the wool material. Before actually trying to pick up the paper with the charged comb, ask the children if they had any idea what will happen when you put the comb next to the paper. The charged comb should attract the paper.
Once you have performed this experiment, you can try adding another dimension to it. Save the paper that you just charged with the comb. Recharge the comb on the wool. Then try to attract the same piece of paper. The paper should "run away." Have students try to figure out what caused this to happen.
Now take the same comb and re-charge it on wool. Then turn the water on gently. Ask the children what they think will happen when you put he comb close to the water. The comb should pull the water. Put the comb near the gently stream of water. If you wiggle the comb around the water should dance. (The Super Science Book of Forces, p.15). Teachers note: This is fantastic when it works, but it is often difficult to perform without practice.
Electronics
Now that the children have been exposed to magnetism and some basic properties of energy, they will begin applying this information to common electronic equipment.
Before beginning these activities, you may want to make journals for the children so they can record ideas, hypothesis, findings, etc as you move through the electronics section of the unit.
The first three activities in this section will require two simple tape recorders, one that is working and can be used by students, and another that does not work.
Activity #1: Using a cassette tape
First, you will spend time working with a cassette tape in a functioning tape player. Begin by recording, playing and erasing sounds on a tape. Introduce students to the concept of "memory." Then present the class with a challenge; ask them to figure out some other types of equipment that would use memory. Some ideas may include; computers, printers, computer disks, VCR, videotapes, compact discs, digital watches, etc. Once the children have generated a list, it is time to test their understanding. Challenge them to explain how the memory actually works.
Since the children have learned that cassette tapes contain magnets, it will also be important to spend some time reviewing that, and allow the children time to hypothesize about why they think that magnet is necessary. Record and save their hypotheses so you can refer to it at the end of the unit.
After completion of activity #4 try re-implementing this activity to see if the children's ideas have changed.
Activity #2: Disassembling a tape player
Prior to beginning this activity, make sure students clearly understand that you are not destroying something that works. Explain to them that it is broken and can not be repaired. Test the machine with the children, to prove to them it does not work. Introduce the class to the tools they will be using. Review procedures for safe usage of tools. The tools you will need are: Small screwdrivers (check to see if you will need Phillips or flat head screwdrivers), needle nose pliers, wire cutters and scissors.
This is the section you will probably spend the longest time working on. Children should be allowed ample time and opportunity to disassemble and explore the parts of the tape player. Using simple tools, students can begin disassembling the nonfunctioning tape recorder to find out which parts combine to record, playback and erase the sounds on a cassette.
The teacher will act as a facilitator for this activity, allowing the children to work as independently as possible (of course taking safety into account). However, you will want to create opportunity for students to work on their critical thinking skills, in connection with the scientific method. Encourage children to create and record hypotheses about the tape player. Then work on ways to prove or disprove each hypothesis. The information gathered here can be recorded in the children's journals.
Save all tape player parts for further activities.
Activity #3: Printing with tape player parts
Use the interesting pieces from the inside of the tape player for printing. Provide shallow trays with thinned paint. Allow children to dip chosen objects into paint and create unique prints. Then display the paintings next to the saved objects from the disassembled tape player. Label all parts on display. This interactive display is a test of the children's visual acuity, see if they can then match up the part of the tape player with the print it makes. You can also provide magnifying glasses for the children to examine the parts with.
Activity #4: Dissecting a computer disk and cassette tape
You will need a 3.5-inch computer disk, an old cassette tape and either a flat head screwdriver or a butter knife.
Choose which item you will be dissecting first. Follow the same procedure for both the disk and cassette.
Begin by looking carefully at the item you are working with. Have the children pretend they have never seen the item before. Ask them the following questions: What parts can you find? Does anything move? What happens when you move those parts? Why? Look for places where the item will come apart. (With the disk, if you remove the metal shutter, you will find some slots where you could gently begin prying it apart.) Open the item carefully, the disk has a small spring that was used to hold the shutter closed, it may jump out when you open the casing.
Once you have opened the item notice the two halves. Ask the children the following questions: Are the halves the same? What parts do you see?
Ask students to draw a picture in their journal of where everything is before going any further. (www.exploratorium.edu_explorer/dissect_disk.html)
Here is a list of the parts inside the computer disk:
-
____
Shutter
-
____
Spring
-
____
Magnetic disk- this is coated with iron oxide which can be magnetized. As
-
____
____
Information is saved on the disk, a recording head creates a magnetic
-
____
____
pattern on the iron oxide.
Hub- the small metal center of the magnetic disk.
Paper rings
Write-protect tab
Plastic flap
Here is a list of the parts inside the cassette:
Magnetic tape- this is coated with iron oxide and can be magnetized, just as the disk can. The recording heads in the cassette player create a magnetic pattern on the iron oxide of the magnetic tape.
____
Hubs- the two plastic wheels that the tape winds around.
____
Write-protect tab
____
Paper or felt (this cleans the tape while its moving)
Spring
(www.exploratorium.edu_explorer/dissect_disk.html)
Take time to compare and contrast the parts of the computer disk and the cassette tape. Ask students the following questions: What parts are the same/different in both items? Describe the functions of the parts? How does the magnet work? How does the computer/cassette player read the information on the disk/tape? Why is there paper or cloth inside? Add any other questions/comments that are appropriate for your group. With these questions in mind, ask students to work independently in their journals. Make the dissected cassette tape and computer disk available for observation while children are working. Finally, have students share their journal entries with the rest of the class.
You that have now completed work with the tape player and thoroughly examined a cassette tape, go back to the activity #1 and repeat some of the lessons. See how the children ideas have changed.
Activity #5: Making an electromagnet
Electromagnets are devices that use electricity to attract or repel objects. (Zubrowski, 64) Electromagnets are used it many types of large construction equipment.
In order to do this activity you will need: a 1 ½ volt battery (Try using a D battery), covered copper wire (check your local hardware store for this), a large nail, tape and some magnetic and non-magnetic objects.
First you coil the wire around the nail. Connect one end of the wire to one terminal of the battery, and the other end of the wire to the other terminal. You can tape the wires on if necessary. If all went well, the nail should now work like a magnet. Test to see what objects it attracts. Once you have tried your electromagnet, try disconnecting it, and see what happens. (Trencher, 44).
(figure available in print form)
How is works: Electricity traveling through the coiled wire and into the iron nail will create a strong enough magnetic field to attract many metal objects (Brown, 168)