Introduction to activity: This activity follows the example elicitation activity What happens with two bulbs?. Part 1 of the development phase is shown below. In this activity students begin to challenge ideas that lead to the prediction that one of the bulbs will be dimmer. One idea that leads to this prediction is that the bulbs use up electricity. One bulb uses up most of the electricity, which leaving the remaining bulb(s) to burn less brightly. This activity also challenges the idea that currents come out of both ends of the battery and clash at a bulb, an idea that emerges when students try to explain how two or more bulbs in series light up. At the end of the activity students are asked to put the ideas that they have developed into an ongoing electronic idea container. This container keeps a record of students' evolving ideas. Later, students are often asked to describe their learning journey using these records of their ideas.

In this on-line sample activity, clicking on links to the “simulators” will open snapshots of the simulator setups in a separate window. The buttons and tools in these snapshots do not work EXCEPT for the four buttons shown to the right (located on the lower right of the simulator image). Clicking on these four buttons allows you to switch between “realistic” and “schematic” views of the simulator, and to “turn on” or “turn off” the current simulation. Dimmed and depressed buttons are inactive.

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CE Activity II - D1: What Effects do Bulbs Have on the Flow of Electricity in Circuits?

Name: Group: Class Period:

	Many electrical devices have more than one circuit element. A string of holiday lights has many bulbs on it, and a refrigerator has both a compressor and a light (and sometimes an ice maker, etc.). In this activity, you will investigate further what happens as bulbs are added to circuits.
	Part I: Adding bulbs in "Series"
	1. In red, trace the path of conductors in the circuit at the right. Notice that both bulbs are in the same continuous path of conductors. In such cases, the bulbs are said to be "in series," and this is called a "series circuit." (Note: if it is more convenient, you can print this page out and use a red pencil to trace the path of conductors.)
	2. Imagine adding a third bulb to the two bulbs in series, as shown in Circuit IV to the right. Predict how the brightness of bulbs F, G and H compare to each other. How did you decide?
	3. Predict how the brightness of bulbs F, G and H compare to bulb B. Copy and paste one of the possible responses from the list on the right.
	Bulb F is bulb B Bulb G is bulb B Bulb H is bulb B							brighter than the same brightness as dimmer than out, so dimmer than
	How did you decide? What is your reasoning about the effect of adding series bulbs on the flow of electricity that justifies your prediction?
	3. Test your prediction. Open Act_II-D1 Sim. The numbers that appear alongside each bulb are an indication of relative brightness, and are included only to help you make relative comparisons. Take a snapshot of the results and paste below. (Note: You may need to reduce the picture to fit below). Keep the simulation open because you will return to it shortly.
	4. Now imagine having four bulbs in series, as shown in Circuit V at the right.
	Predict how the brightness of bulbs I, J, K, and L compare to each other.
	Predict how bulbs I, J, K and L each compare with bulb F from the previous (3-bulb) circuit.
	How did you decide? What is your reasoning about the effect of adding series bulbs on the flow of electricity that justifies your prediction?
	5. Test your prediction. Go back to the Current Electricity Simulator. Delete the two circuits, and set up the new circuit. Run the simulation in the Realistic View. The brightness numbers should help you compare the brightness of each of these bulbs to their brightness in the previous 3-bulb circuit. Take a snapshot of the results and paste below. Do not close the simulator.
	6. In science, explanations are the means we use to communicate our reasoning: how we know what we know, or why we believe certain things to be true about the natural or human-made world. Scientific explanations usually involve stating observations accessible to us and our senses, and then logically and imaginatively constructing a conclusion or generalization consistent with the observations. Based on your observations, state two generalizations. The first should be a generalization about how identical bulbs in a series circuit compare in brightness with each other. The second generalization should be about what happens to the brightness of each bulb in a series circuit as the number of bulbs in the circuit increases.
	Generalization #1: Generalization #2:
	7. The next step is to construct a mental or conceptual model about what is happening. Open the Cycle II Idea Journal and use the evidence from this activity to support your initial ideas, modify them, or add new ideas about the effect of bulbs on the flow of electricity.
	Part II: Adding bulbs in "Parallel"
	You have been working with bulbs all in the same loop of conductors. There are other ways to connect up two bulbs and a battery, as you saw in the Elicitation activity. You will explore this new method to help you develop your model of what effect bulbs have on the flow of electricity.
	Materials: three bulbs in sockets, two batteries in holders, hook-up wires
	1. In red, trace the path of conductors from one side of the battery, through bulb D, to the other side of the battery in Circuit III at right. In green, trace the path of conductors through bulb E. Notice that each bulb has its own conducting "loop". In such cases, the bulbs are said to be "in parallel," and this is called a "parallel circuit". (Note: if it is more convenient, you can print this page out and use red and green pencils to trace the path of conductors.)
	2. Imagine adding a third loop to the two bulbs in parallel, as shown in Circuit VI below.
	Predict how the brightness of bulbs M, N, and O compares with each other.
	Predict how the brightness of bulbs M, N and O compare with the brightness of bulb A in circuit I. Copy and paste one of the possible responses from the list on the right.
	Bulb M is bulb A Bulb N is bulb A Bulb O is bulb A						brighter than the same brightness as dimmer than out, so dimmer than
	How did you decide? What is your reasoning about the effect of adding parallel bulbs on the flow of electricity that justifies your prediction?
	3. Test your prediction. Set up Circuit III, then add a loop to make Circuit VI (make sure the batteries and bulbs are as identical as possible).
	Pay attention to any large differences, rather than small differences that could occur if two of the "identical" bulbs are, in fact, not identical.
	For additional feedback, go back to the simulator, set up the circuit, and run the simulator. Take a snapshot of the results and paste it below. Do not close the simulator.
	4. Imagine having four bulbs in parallel, as shown in Circuit VII below. Predict how the brightness of bulbs P, Q, R, and S compare to each other, and to bulb A from Circuit I.
	How did you decide? What is your reasoning about the effect of parallel bulbs on the flow of electricity that justifies your prediction?
	5. Test your prediction. Go to the simulator, and set up the circuit. Run the simulation, take a picture of the results and paste them below. Do not close the simulator.
	6. Based on your observations, state a generalization about the relationship between the number of parallel bulbs in a circuit and the brightness of the bulbs.
	7. The next step is to construct a mental or conceptual model about what is happening. Open the Cycle II Idea Journal and use the evidence from this activity to support your initial ideas, modify your ideas, or add new ideas about the effect of bulbs on the flow of electricity.
	Part III: Adding a wire around a series bulb
	In Cycle I, you investigated what happens when you added a wire around a bulb in a one-bulb circuit. What would happen if you tried this with a series circuit?
	1. Imagine starting with two bulbs in series (Circuit II), and putting a wire around bulb B. The situation would look like Circuit VIII below.
	Predict how the brightness of bulbs T and U will compare with the brightness of bulbs A, B and C. (You can copy and paste from the phrases shown to the right:							brighter than the same brightness as dimmer than out, so dimmer than
	Bulb T is bulb A Bulb T is bulb B Bulb T is bulb C			Bulb U is bulb A Bulb U is bulb B Bulb U is bulb C
	How did you decide? What is your reasoning about the effect of bulbs on the flow of electricity that justifies your predictions?
	2. Test your prediction. Set up Circuit I and Circuit II. Then place a wire around bulb B to make Circuit VIII. (Make sure all bulbs and batteries are as identical as possible!) What happens if you place the wire around bulb U instead of bulb T? To obtain additional feedback, go back to the Current Electricity Simulator, delete all the other circuits, and set up this new circuit VIII. Run the simulation, take a picture of the results and paste it below.
	3. Summarize the observations and conclusions from this investigation.
	4. Open the Cycle II Idea Journal. Modify your ideas about the effect of bulbs on the flow of electricity in circuits, citing the evidence from this part of the activity, or add supporting evidence for previous ideas.