This year, we created a new lab practicum for the circuits unit. In addition to the traditional activities of having students draw a circuit diagram from a written description, build the circuit, and measure the voltage across and current through a specified resistor; students had to infer the circuit diagram for a collection of lightbulbs based on their observations.

This activity was inspired by an old Science Olympiad circuits event. As shown in the following photo (which is somewhat hard to discern due to the pattern of the fabric), four labeled light bulbs protrude through holes in the fabric. The fabric hides the wires connecting these light bulbs. Students turn on the power and then make observations by unscrewing and screwing in the light bulbs. Based on their observations, they draw the circuit diagram and justify their conclusion.

Students were most engaged in this activity of the lab practicum compared to the others. I think the fact that it was a unique way for them to apply their knowledge and inference abilities made it so interesting. It also had the unexpected benefit of reinforcing the idea that physical order of the light bulbs has no effect on their brightness. That is, the first light bulb in series from the positive terminal of a battery is not the brightest because it is “first.” Several students commented that there were several circuit diagrams that they could draw that would match their observations. It was reassuring that they came to this conclusion!