Recharging Batteries & Bulbs
by Alan Colburn
Batteries & Bulbs is a classic unit for teaching students about electrical circuits. It first appeared as a unit in the Elementary Science Study (ESS) curriculum. This adaptation of the unit is closely aligned with the vision of science teaching espoused in the National Science Education Standards. Youll see that the unit responds to individual student experiences, focuses on student knowledge and its application, includes students being involved in extended inquiry, involves continual assessment of student understanding, and its fun!
You can begin the activity by asking students how they would connect a battery, bulb, and wire to make the bulb light. Have the students draw a picture, and then compare pictures with other students in the class. This will get students thinking about their knowledge of electrical circuits (even if they arent familiar with the term).
Students come to class with many ideas about how the world works. Many of these preconceived notions seem perfectly reasonable, though they differ from the scientifically accepted ideas. The drawing on the right is the most typical response. Although this combination does not light the bulb, it seems reasonable to think electricity leaves one end of a battery, travels through the wire, and becomes light. Without close inspection, for example, this is how a flashlight seems to work. This activity helps students start thinking about their conceptions of electricity and electrical circuits.
At this point, students will be ready to test their ideas! Give them instructions to make the bulb light, using only the battery, bulb, and piece of wire you supply.
Finding out that some ideas dont work helps students see the deficiencies in their thinking. This is the first step toward conceptual change. Students must see whats wrong with their ideas before being ready to really accept a new view. Eventually, however, all or almost all students will be able to light their bulb.
Modify and test again
Once a student (or group of students) lights a bulb, give them the instructions to find other combinations of battery, bulb, and wire that will light the bulb. Have them draw diagrams for all the combinations they try, noting whether the bulb lit. Students will do things like turn the battery around, connect different parts of the bulb to the battery, and connect the bulb to the opposite side of the battery.
These further activities that students go on to do require them to think about other ways to get a bulb to light. They begin to see patterns about requirements to light the bulb. As the teacher, you can ask questions about what patterns students are beginning to see. Some students will be able to predict whether a bulb will light but not necessarily provide rules or a clear explanation for why the bulb lights in some circuits and not in others.
Predicting and recording
Now students have experimented to figure out combinations of the materials that will light the bulb. They recognize circuits that will and wont light. They are ready to be given a prediction sheet with combinations of materials and asked whether each combination will or wont light. Students should test their predictions. You can find these sheets from a variety of sources. See the references at the end of the article.
Looking at these sheets, while students are working, gives you a way to begin assessing what they are learning. In addition, by asking students about what theyve written, you gain further information about their new understanding of electrical circuits.
Series or parallel?
The next step is for students to figure out how to light two bulbs at once. Now the task gets a bit more complex. There are two arrangements of a battery and two bulbs that will light both bulbs at once, series (photo on left) and parallel circuits (photo on right). (These photos have the bulbs in sockets with clips for wires.)
In a series circuit, electricity "flows" from one bulb to the next. This is how Christmas tree lights used to be wired, back in the days when a burnt out bulb meant testing every bulb, because none of the bulbs lit if even one burnt out. Frequently, this is the kind of circuit students will build when given the instructions above. In a parallel circuit, on the other hand, each bulb is connected directly to the battery, each bulb has its own circuit, you might say. If one bulb burns out (or is taken from the circuit), the other bulb remains lit.
You can then ask students to figure out how to light two bulbs so that they can remove one bulb and the other will stay lit. If students have already built a parallel circuit, you can simply tell them to find another way to light two bulbs. The goal is for students to have created both a series and a parallel circuit.
The learning cycle model
Youll notice that in the activitys procedure so far there is no point where students read a textbook or listen to a lecture about electrical circuits (or any other aspect of electricity). When should the teacher do that, assuming the teacher is interested in introducing this content? Now! The reason lies in a well established model of teaching and learning called the learning cycle.
This model, which can (basically) be traced back to SCIS, the Science Curriculum Improvement Study, is an approach to instruction centered on two overarching principles. First, students will learn new ideas better if they have first had relevant concrete experience. In this case before you introduce the ideas of a complete electrical circuit, series, and parallel circuits, students should have experience with the material.
The second broad tenet of the learning cycle approach is that learning is maximized if you then do something with the new ideas, preferably in a different situation. With Batteries & Bulbs, this leads to the idea of introducing the new content at this point in the unit. Once introduced to the ideas, students will go on to use the concepts while exploring switches and their effects when placed in different parts of series and parallel circuits.
Experiments with switches
Students can be challenged to figure out how simple knife switches work, and what happens to bulbs when switches in circuits are opened and closed. As with the first step, students making predictions before testing their thinking is suggested.
Since students have been learning by experimenting with materials, trying to answer questions, it makes sense to assess their learning the same way. You could ask students to make a particular circuit, as part of a quiz. You can even make assessment be part of the unit itself. This last step introduces students to switches; the same activity can also form the basis for (part of) your assessment of student progress. Choose a task that is (a) novel, yet (b) one you believe most students will be able to complete.
Making a diagram or drawing of their work allows students credit if they cannot make a circuit that "works" as directed. It also gives you the chance to further understand their thinking and decrease the chance of students merely copying neighbors circuits. (In addition, logistically, the entire class does not have to take the "quiz" simultaneously. Part of the class can be engaged in some other activity.)
Information from this quiz/activity is only one piece of the information you get from students during the unit. You also have the prediction sheets they filled out earlier; these, too, can be graded if you need to do so.
In addition, the adequacy of responses to a carefully chosen question or two asked of each student during the unit can also count toward a grade. Youre probably asking students questions as they work anyway. Thus, what I suggest here is merely a spot check to record a little information about how well students responded to your question(s). Teachers often find a clipboard with a brief space next to each students name makes this type of assessment realistic.
There are many ways to continue this unit. Students can make increasingly sophisticated circuits, experiment with mystery boxes in which they figure out what electrical devices are wired inside a cardboard box, or move on to the study of magnetism. The references listed below will help you. I have found that this work offers truly enlightening experiences for teacher and students!
Elementary Science Study (1966). Teachers Guide for Batteries & Bulbs: introduction to electricity and magnetism. Delta Education, Nashua, NH. 1-800-442-5444.http:www.delta-ed.com
Electric Circuits: Teachers Guide (1991). STC, National Science Resources Center. Student books, teachers guides, and materials are available through Carolina Biological Supply Co., 1-800-334-5551.http://www.carolina.com
Stepans, J. (1994). Targeting Students Science Misconceptions: physical science activities using the conceptual change model. Provides both activities and information about misconceptions students bring with them to class. Idea Factory, Inc., Riverview, FL. 1-800-331-6204.
Electricity. TOPS Learning Systems 10970 S. Mulina Rd, Canby, OR 97013. Low cost ways for students to study electrical circuits; a module about magnetism is also available.http://www.topscience.org
- Alan Colburn is an assistant professor of Science Education at the California State University in Long Beach. Among other duties, he teaches science activities, including those in this article to current and prospective K-8 teachers.