Before we move on, I will have students act out the movement of electrons in a circuit, using ping pong balls as electrons. Note: click here for background information on electricity.
Batteries and Bulbs Learning Cycle
Engage. As I pass out the materials to each pair of students, I will tell the students that they have been spelunking -- wearing a light on their helmet -- when they run into an overhanging rock and smash their light. In the complete and utter darkness, they feel around and locate a battery, a bulb, and two pieces of wire. In order to find their way out of the cave, they need to make the bulb light with only these supplies.
Explore. During this phase, students will "play" with their materials trying to find a way to make the bulb light. If a group gets the bulb to light, I will get them to try it with only one wire. ("Oops, you dropped one of your wires! See if you can still get the bulb to light.")
Explain Together During this phase, I will help the students make sense of what they have experienced. Groups will be invited to come to the board to draw designs that worked and ones that didn't. What did the designs that worked have in common? Initially, I will work towards the concept of the circuit, introducing the terms:
conductor: a material through which electricity can flow easilyI will use a few of the attached diagrams of battery bulb set-ups (will they work or not?) as a formative assessment at this point. Misunderstandings can be cleared up here before going on. It is important to test our ideas against the drawings of successful and unsuccessful designs on the board. Next, I will have the students look closely at the light bulb itself. How might it be "hooked up" inside? Their responses will provide me with some more insight about what they understand, and I can clarify concepts here as well. Then I will draw a large diagram of a bulb and battery system on the board and have them work out the internal wiring, discussing what parts might be insulators and what parts might be conductors. The finished drawing might look like this:insulator: a material through which electricity doesn't’t flow easily
circuit: a continuous path of conductor so that electricity can flow from one end of the battery, through the device (light bulb) and to the other end of the battery
short circuit: a circuit that by-passes the device (light bulb), that is one where the electricity can flow from one end of the battery to the other without going through the device.
Before we move on, I will have students act out the movement of electrons in a circuit, using ping pong balls as electrons. Note: click here for background information on electricity.
Expand. Once we know something about circuits, students should be able to create a situation where an open circuit can be turned into a closed circuit with a switch. Materials to make switches will be available. Depending on how quickly they take to the task, I may make suggestions about some types of switches, such as pressure switches, turn switches and tilt switches. Students write an article for the paper describing their adventure and including a diagram of their switched circuit in both the open and closed circuit position. The article should include a description of how and why the switch works, using the appropriate vocabulary.
Evaluate. The formative assessment will occur throughout the lesson, but I will pay special attention to the discussion after the conceptual invention phase of the lesson. Getting them to analyze the light bulb will provide another opportunity for formative assessment. Problems requiring remediation should be apparent. The expansion phase of this activity acts as the summative assessment. A careful analysis of their writing as they describe their open and closed circuits will allow me to determine any remaining weaknesses in their conceptual models of circuits.