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Home-made Generator

Author: Mark Roland, generator design and experimental ideas from ScienceProject.com


Time:

3 class periods

Preparation Time:

2-4 hours, depending on number of students

Materials: For each lab group:
One rod magnet 3” long (at least one of differing strength)
2 Pieces of balsa wood, 3.5” x 3.5” x 1/8”
4 pieces, 1” x 3 7/16” x 1/8”
**-last two can be cut from a sheet of 1/8” thick balsa
wood that is 3.5” by 1 ft. with very little waste
6” piece of 3/8” diameter balsa wood dowel
3/4” piece of 1” diameter balsa wood dowel
200’ of Insulated copper wire 27 AWG (at least one spool of a different size, around 35 AWG)
1.2 V light bulb with base
Wood Glue

NOTE—Preparation time can be greatly reduced at a cost. Kits for these generators are $25 a piece, available at miniscience.com. The materials listed should cost about $5, maybe less if you buy bulk for multiple kits.

Abstract
This experiment is a great chance for students to design their own experiments. On the first day of the lesson, students will build their own electric generators. This involves some drying of glue, so it might be a good idea to work on this before hand. If you have time at the end of any lessons, the first steps of construction could be done in order to allow the glue to dry.
Once the generators are completed, students will come up with a testable question, a hypothesis, and they will design an experiment to test this hypothesis. This is an excellent inquiry lesson.

Purpose – The purpose of this lesson is to explore the idea of electromagnetism, and to practice the ideas of scientific inquiry.

Objectives
Students will be able to:
1. Design and conduct an experiment related to electrical generation.
2. List the factors that affect the amount of current that can be generated by a simple generator, such as the number of turns of wire, the strength of the magnet, and the speed of rotation.

National Science Education Standard:
Content Standard A-Science as Inquiry
ABILITIES NECESSARY TO DO SCIENTIFIC INQUIRY
• IDENTIFY QUESTIONS AND CONCEPTS THAT GUIDE SCIENTIFIC INVESTIGATIONS. Students should formulate a testable hypothesis and demonstrate the logical connections between the scientific concepts guiding a hypothesis and the design of an experiment. They should demonstrate appropriate procedures, a knowledge base, and conceptual understanding of scientific investigations.

• DESIGN AND CONDUCT SCIENTIFIC INVESTIGATIONS. Designing and conducting a scientific investigation requires introduction to the major concepts in the area being investigated, proper equipment, safety precautions, assistance with methodological problems, recommendations for use of technologies, clarification of ideas that guide the inquiry, and scientific knowledge obtained from sources other than the actual investigation. The investigation may also require student clarification of the question, method, controls, and variables; student organization and display of data; student revision of methods and explanations; and a public presentation of the results with a critical response from peers. Regardless of the scientific investigation performed, students must use evidence, apply logic, and construct an argument for their proposed explanations.

Content Standard B-Physical Science
MOTIONS AND FORCES
• Electricity and magnetism are two aspects of a single electromagnetic force. Moving electric charges produce magnetic forces, and moving magnets produce electric forces. These effects help students to understand electric motors and generators



Related and Resource Websites
http://www.scienceproject.com/A/projects/KITWG/index.asp (Generator design)

 

 

Activity

Preparation:
These steps would be difficult to do as a class. If you have the equipment necessary and a relatively small class, it could be done. Perhaps a wood shop teacher would be willing to help you out.

If you are buying a kit, all the wooden parts are included and they are already cut to size. So you just need to connect them. If you don't have a kit, prepare the wooden parts as follows:
1. Cut two square pieces from the 1/8” balsa wood (3.5" x 3.5").
2. Make a 3/8" hole in the center of each square.
3. Cut four squares 1" x 3 7/16” from the 1/8” balsa wood.
4. Cut a 3/4" piece from the 1" wood dowel. Make a 3/8" hole in the center of it. Insert a 6" long 3/8" wood dowel in the hole, and apply some glue. Place it about 2” from one side of the 3/8” dowel and wait for it to dry.
5. Make another hole with the diameter of your rod magnet in the center of the larger wood dowel piece for the magnet to go through.

Wood dowels after completing step 4
Wood dowels after completing step 5

If it is necessary for you to prepare the kits yourself, the process could be streamlined. Try cutting multiple pieces of the same size from a large sheet, minimizing your cuts. Once the kits are prepared, you can begin the lesson.

Day 1
Construction of the generator: These steps are taken directly from the website, as is the picture.

1. Insert the magnet in the hole of the wood dowel. Center it and use some glue to secure it.
Note—make sure one group has the magnet of differing strength.
2. Use one large square balsa wood and four smaller rectangular balsa woods to make a box.
3. Insert your wood dowel into the hole in the center of the box. At this time the magnet is inside the box.
4. Place the other large square to complete the box. Apply some glue to the edges and wait for the glue to dry. By now, you have a box and inside the box you have a magnet that can spin when you spin the wood dowel.
5. Wrap 200 turns of copper wire around the box and use masking tape to secure it, leaving both ends free.
6. Remove the insulation from the ends of the wire and connect it to the screws of the bulb holder or base.
7. Insert the light bulb
8. Spin the wood dowel fast to get the light. Here is a picture of a completed generator:

If students finish before the end of the class period, allow them time to work with their generators. Ask them to think about a testable question that they have about the generators. In other words, ask them to hypothesize about what they could change in their design in order to alter the output of the generator.

Day 2
Experimental Design

1. Each group should come up with a testable question. There are not a lot of variables to change, so some groups will be testing the same thing, which is OK. Some possible variables include the number of turns of wire, the strength of the magnet, the diameter of the wire, and the speed of rotation of the magnet. Work with each group and ask them what question they plan to test.

Note—One group will have the magnet with a different strength. This group will not be able to rebuild their generator with a different one. I would suggest pairing this group with another one that has a regular magnet, and having them design a slightly different experiment. They will already have two different generators of different design, which would make testing the effect of magnet strength pretty easy. For that reason, I suggest having them test this effect under different conditions. Both groups should change the number of turns, and then test. Then both groups should change wire diameter, then test, etc.

2. Once they have a testable question, based upon their previous experience with the generator, each group should form a hypothesis. Try to make these hypotheses as specific as possible. For example, if they are testing the number of turns of wire, will doubling the number of turns double the current, or will it quadruple it? Don’t just say it will increase or decrease.

3. Again, check the progress of each group, and then ask them to write down the steps for an experimental design. Things to keep in mind while designing their experiment:
a. What are the independent and dependent variables?
b. If one of your variables is the amount of current generated, how will you test and record this?
c. What tables, graphs, or charts might be useful to design now in order to better organize your collection of data? How many data points are necessary?
d. What results do you expect to see?

4. Monitor each group, and make sure that they have a workable experimental plan.
5. Once each group’s plan is checked, allow them to begin experimenting. They should have time to begin on their experiments, but will most likely not finish them.

Day 3
Experimenting and Closure

1. Students can begin the class where they left off the day before. Monitor the class, ensuring that they are staying on task, and asking any questions that arise. Make sure that students are collecting enough data, and arriving at specific conclusions.

2. As groups are finishing, they may begin writing conclusions. Was their hypothesis supported or not? If not, what happened instead? What other questions arose while conducting this experiment? How could you test these questions?

3. Discuss the results of the experiments as a class. Make sure that the main questions from the objective are answered. What is the effect of more turns? Stronger magnets? Different diameter wire? Can we write a formula to summarize these results numerically?


Embedded Assessment
This lesson can be assessed in many ways. I would suggest a short quiz on the information gathered as a class a few days after this lesson. Also, a formal written lab report should be completed in some format, because it will be necessary to measure the first objective. This should be in whatever format you have used with your students in the past. There is a laboratory grading rubric available on the website that might provide some ideas.

Embedded Assessment

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 







PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:


an
NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award

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