Bursts of Energy...
Electricity & Magnetism

Making a Switch

Goal: Students will gain knowledge of electrical circuits by experimenting with a switch.

Process skills: Observing.

Frameworks: Force and Matter

Materials: (for each switch)

1. one empty wooden thread spool (or a one-inch section of a wooden broom handle with a hole drilled through the middle)
2. two metal washers one long screw
3. two short flat head nails
4. 2" x 2" piece of wood
5. aluminum foil
6. two paper clips

Teacher background information:
This switch is a variation of one invented by Lewis Latimer, an African-American inventor who was one of the early pioneers in electric lighting. Latimer was a highly respected engineer at the Edison Electric Light Company. Researching Latimer's career would be a good way for students to learn about the challenges of bringing electrical lighting to the world.

This activity is offered to provide students with an opportunity to build a simple device. If you choose not to build them in class, these switches are inexpensive and can easily be made in quantity ahead of time for classroom use.

Procedure:

Students will:

1. Cut a strip of aluminum foil long enough to go two-thirds the way around the spool and wide enough to cover the main body of the spool. (The spool flanges must remain uncovered.) Spread a thin layer of glue completely over the back of the foil and carefully glue it to the spool.
2. Attach the spool to the piece of wood with the long screw, placing the washers above and below the spool. Leave the spool loose enough to turn easily. (See Figure 1.)
3. Pull the two parts of the paper clip apart so that the two bends are about 1 cm apart. (See Figure 2.)
4. Using the two small nails mount the clips to the wood block. The clips must be placed on opposite sides of the spool so that one leg of each clip presses lightly against the spool. (See Figure 3.)

Discussion:

1. Describe how to use this switch. Where would circuit wires connect to the switch?
2. What other ways can you think of to control the flow of electricity?
3. What things in your home are controlled by switches?

Figure 1.
block

Figure 2. paper clip

paper clip (unfolded)

Figure 3. When both clips touch the foil, a circuit is made. When you tum the spool only one clip touches the foil, the circuit is broken.

wire
bent paper-clips press against spool and wire attaches to nail.

Teacher resource:
Bingham, Jane. The Usborne Book of Science Experiments
Gr. 3-6. The book contains many easy-to-follow projects and activities with complete explanations and discussion.
ISBN: 0-7460-0806-6