Previous understandings:
Students should be familiar with the following concepts: energy, electricity (as representative of the transfer of energy from one place to another). Students should have previously learned that light indicates the presence of energy. These lessons are best taught following units on magnetic forces and static electricity.
Investigation 1: Why did the lights go out? Electrical currents as a way to transfer energy from one place to another.
Materials: string of decorative lights cut into sections (make sure they are wired as a series circuit), AA batteries, Investigation 1 Lab Sheet (optional), ammeter (optional)
Instructional Sequence:
Begin the lesson with the classroom lights turned off. Try to make the classroom somewhat dark (without being too disruptive), such that the lights being off creates a mild problem(s) for students (e.g., not being able to find something in their desks easily, not being able to see the board- note that you can make this an intermittent problem, and have the lights come back on periodically, if you want students to do this lesson in chunks over days, instead of continuously). Give students an opportunity to ask why the lights are off. Tell students that the lights went out suddenly, and we don’t know why- some scientists and engineers are working on the problem, but aren’t sure what happened to cause the lights to go out, or what to do to solve the problem. Tell the students that the original plan for the class time was to do something that requires the lights/power being on (e.g., make observations and describe something, read a book the kids are excited about, an art project, a play- you can tie this into something they will be doing later on anyway, to make it more authentic, but try to frame it as something the students are excited about doing, so that they care about fixing the problem), but now they won’t be able to do it until the lights come back on. Ask students if they would like to try to help figure this problem out.
As a class, ask students to describe the system they are working with, including:
- The problem, as described by the parts (components) that are involved (e.g., lights, the space to be lit, the boundaries of the problem [e.g., only this classroom doesn’t have lights])
- What we know about the problem and those components (e.g., the presence of light indicates energy; electric forces interact with charged objects; this can include students prior knowledge and help draw out misconceptions to be addressed over the course of the lesson).
As students are sharing their ideas, draw a diagram that includes their thinking to help guide the next conversation. At the end of the share out, use the diagram to frame the following, with student participation: when light is present, it indicates that energy is present; when the lights are turned off, that energy isn’t there- if we can’t turn the lights on, that must mean the energy can’t get to the room for some reason. Where does the energy come from, and how does it get to our classroom?
Give students a few minutes to think independently about these questions, and to note down their ideas in whatever way they would like to. Then have them share their ideas with a small group (~4 students)- as you walk around, listen to students share their thinking, noting misconceptions that the lesson should help address (e.g., that the energy magically appears; limited understandings, like the energy comes from light sockets). After students have had some time to think about these questions, ask them (as a group) to write down their favorite three ideas from their group on a sheet of paper, to come back to as a group as they continue their investigation. As a class, ask students to think about the ideas their group came up with- while many of them could be contributing, there is probably a specific problem with the lights in their classroom- how could we begin testing for those problems? Allow students time to share out some ideas to the class, many of which will likely involve testing the classroom or lights themselves. Tell students these are great ideas, but we can’t test the classroom and lights themselves because we want to make sure the scientists and engineers can investigate the problem too. Instead, we can use a model- something to represent the problem- to help us think about what the problem might be, and how to fix it. Return to the class diagram you made previously, and remind students what they thought the important components of the problem were- we should make sure that whatever we use to model the problem includes these components. Show students a variety of materials in the classroom (including the string of lights)- ask them to think about which one might model the problem the best. Use student thinking to guide them toward choosing the string of lights (e.g., because it has lights that can turn on and off).
Ask students to go back to the problem diagram and their ideas about what was responsible for it- how can we turn those ideas into testable questions? Give students an opportunity to think about this on their own, and then in their small groups. You can either walk around and help the small groups get to a set of questions you want them to think about, or do this as a whole class. These questions should include the following ideas:
- How do we make the lights (as a model for our classroom) light up?
- What is the source of the energy in the system?
- What do we have to do to make the lights go out when they are already lit up?
- How do we know the bulb isn’t just broken?
These questions should guide student investigations, and can be used to frame discussions.
Ask students to work with a partner or small group to first figure out how to cause the string of bulbs to light up. Tell students that we need to be able to tell the other scientists and engineers what worked, didn’t work, what we observed, and evidence to support our thinking to help solve the problem, so we will record our findings in our notebooks (just like the other scientists and engineers will be doing). Provide students with the materials, and remind them to draw diagrams of the circuits they try out, record whether the light bulbs lit up or not, and any observations that they make while figuring out how to make the lights light up.
Bring the class back together and take a few minutes to review their experiences: How did you get the light bulbs to light up? What different ways did you try to light up the bulbs? If you were telling a friend how to do it, what advice would you give them?
Have students return to their diagram of how they got the lights to illuminate. Let them know that they will be making a model of their design by drawing a diagram that they can use to test their ideas. Models are helpful tools for representing ideas, and will help them to demonstrate their understanding of how electrical current transfers energy to the light bulb in a circuit. Ask students to add descriptions of their thinking to their diagram to explain the energy transfer that is taking place, including:
- The energy source
- Where the energy is going, including the path the energy follows (use this as an opportunity to make sure students understand that wires have to form a closed ‘circle’ with the two ends of the battery and the lights-although this is not something they need to explain, it will be important for them to observe to complete the learning goals- you may want to think about this as a constraint of the design from an engineering perspective. Because students aren’t expected to understand electrons and electron flow (current) as the result of subatomic particles, keep the emphasis on current as a way to transfer energy, and batteries and a source of stored energy. In third grade, students should have had some exposure to electrical forces and charged objects, which may be helpful to bring in here. It may be helpful here to link this kind of thinking to other energy transfers students have learned about, like plant/animal systems- this can help keep the learning and conversation conceptually focused without introducing too many black boxes).
Make sure students know that they are diagramming their thinking, and it’s okay if it changes with more information/investigations.
After students have diagrammed their thinking, ask them to make a prediction, based on what they know right now, about what would cause the lights (or some of the lights) to go out? Ask them to present their thinking about this to one other group by making a human version of their model. One student will be the battery, one student a light, and 2 students will be wires. In their presentations to the other group, ask them to first demonstrate how the normal circuit would work (essentially demo-ing what they observed), to describe their prediction about what would make the light not light up, and then demonstrate their thinking behind the prediction using the human circuit. As you walk around, listen for student thinking and misconceptions, and use questions to guide students to think about 1) the idea that the wires (and electrical current/charges flowing through them) is transferring the energy from the battery to the light bulb, and 2) how this provides evidence/reasoning for their predictions.
Now ask students to relate that thinking back to the current task: in our school, our classroom doesn’t have working lights, but the rest of the school does. That would be like if one light, in our string lights model of the problem, represented our classroom- now that we know what is necessary to transfer the energy to the light, and we have made predictions about how we would ‘break’ that circuit, we will use our knowledge so far to investigate what is going on with our classroom. Ask students how we could model this using the string of lights? Use student answers to decide that this time, we are going to keep everything the same in our working circuits, and just remove one of the bulbs. Ask students to make and record observations as a group- Do the other lights illuminate? Why or why not? Discuss with your group, use your diagram to help you. Ask students to relate what they see back to the classroom problem.
Bring the class back together to discuss their findings and predictions for why the string no longer lights up. What patterns did they observe in both parts of the investigation? What do they think is causing the lights to light up or not light up, based on their observations? How could this be similar or different to the classroom experience? How could we use our knowledge to think about the classroom lights, using the string of lights as a model? Ask students to record their thinking in their notebooks, citing the relevant observations from their investigations and models as evidence to support their ideas.
Assessment: Students’ diagrams, models, share outs, and written responses in their notebooks can be assessed for their understanding of the necessary elements of energy transfer via electrical currents to cause bulbs to light up. Any misconceptions that students have can be addressed either one on one, or as a whole class at the beginning of the next investigation. The primary focus of student thinking now should be around wires (and the currents within them) as a way to transfer energy from one place to another- in this case, from the battery to the light.
Investigation 2: Design a String of Lights as a Model for the Classroom
Materials: string of decorative lights cut into sections (make sure they are wired as a series circuit), AA batteries, wire strippers/cutters, goggles, “How Does Electricity Flow? Investigation 2 Lab Sheet
Instructional Sequence:
Review the basic problem and concepts with students: What did we learn last time? How did you make the string of lights light up? What happened to the electrical current when we took a light out of the string? What are some predictions we have for why that happened? Draw a diagram of energy flows from the battery to the string of lights. Ask students if this diagram- and the string of lights- makes sense as a model for the lights going out in their classroom. As students share their ideas, encourage them to think about the other classrooms and the hallway, and what they observed with the string of lights- did all the lights after the removed bulb go out? Did the lights go out in the hallways/classrooms around them? Encourage students to see that in the school, there is power to the other rooms (in the model, represented by other light bulbs), but not in the string of lights. Ask students why they think this is true- and then tell students that they can investigate further with the string of lights to figure out how the room/school is wired, to help figure out what the problem is.
They will be designing a solution so that the string of lights will work, even with one bad/missing bulb, as a model of what is happening in their classroom to help scientists and engineers develop a solution for their real life problem and turn the lights back on. Next, ask students what constraints they have? What might limit their options for their design? (i.e. time, materials, etc.) What are the required features (criteria) of the design? Ask students to note these down, as they will have to discuss whether their solution meets these criteria and constraints. Remind students that designing and engineering is a process, and they will need to try different strategies to test if they work. Students should sketch out and label diagrams of the different iterations that they test, and note whether or not it worked; this will help them to keep track of what they have tried, and will help guide their discussion with their partner/group. Remind students know that their diagram is a model. It is a helpful tool for representing ideas, and will help them to demonstrate their understanding of how electrical current works in a circuit to transfer energy from one place to another.
Students will then work with their partners or small groups to design and test out different ways of wiring the string of lights, based on their observations. The teacher will walk around the room as students are working, observing their conversations and asking questions to guide their thinking. If it seems like the students are struggling, you may want to invite them to revisit acting out a circuit. Draw their attention to the difference between an open and a closed circuit, and ask them to brainstorm some ways that a circuit may become ‘open.’
Once students have determined a design that works, have them draw out and label their final diagram. Ask them to compare their diagrams from both investigations- what is similar? What is different? Students should be able to describe that in the first diagram, energy had only one path to flow through- through the wires to each of the bulbs in order. In the second diagram, students should be able to describe that to allow the other lights (after the broken/removed bulb) to turn on, there had to be a way for the energy to flow from the source to those bulbs without first hitting the removed bulb (and also complete the circuit and go back to the battery). Ask students which diagram models their class room better? Why?
Recap with students what they have discovered so far:
- For a light (which indicates the presence of energy) to turn on, energy must be transferred to that place
- Energy has to be able to flow directly from the source to the target- if anything interrupts this, the circuit doesn’t work
- Wires carry electrical currents, which transfer energy from place to place
- Based on what they know, the school must be wired with each room directly connected to the energy source, not a single connection that goes from classroom to classroom.
Ask students to brainstorm some ideas about what could be causing the power outage in the classroom, and some possible solutions based on their findings. Encourage them to look back to their previous diagrams and notes- what were their initial thoughts? Does the evidence support any of them? Why or why not? Ask students to independently write a letter or report for the scientists and engineers working on their classroom, including:
- A simple sketch of what the wiring to the classroom might look like (power source, classrooms on either side, the given classroom)
- A description or indication of where the problem likely is in the circuit involving the classroom(e.g., not at the power source, but between the power source and the specific classroom)
- Some possible ways to fix it and why they think that might work (note: this will be purely to encourage student excitement and buy in- you may let them be as creative as you wish, but look for rationales that include the science and engineering ideas they used here).
Provide students with the following checklist to include in their explanation:
- I explained how energy travels to the light bulbs in both the original circuit and the new circuit design.
- I explained why the other bulbs stay lit even if one is removed (for the new design).
- I used my diagrams, class discussions, and models as evidence for my ideas about what is happening in our classroom.
Assessment: Students’ understanding of energy transfer via currents will be evaluated based on their final labeled diagram of their design, and their written description of how energy flows within their designs, as a model for the classroom.
To wrap up this lesson, a few hours later (or the next day), turn the lights back on suddenly, and read a letter to the students from the scientists and engineers detailing how helpful their suggestions were, and how they solved the problem using the information the students provided them with. In this activity, if you would like to probe students thinking around the CCCs and understanding energy transfer, you could pose a final problem the scientists want the students to explain, involving energy transfer from place to place, indicators of the presence of energy, and an appropriate CCC.
