In this lesson, students will use a circuit tester to determine whether objects are conductors or insulators. To begin the lesson, I model the process of creating a circuit tester on the document camera. As I work, I have students work alongside me. This ensures that every student has a functioning, properly constructed circuit tester with which they can complete the remainder of the lab.
To create a circuit tester, I guide students to build a simple circuit as they have done in previous lessons. I then ask them to disconnect the wire between one side of the bulb socket and battery holder. I have the students add a third wire to the battery holder so that there is an open space between the battery holder and bulb socket that can be bridged by the wire. To ensure that the tester is working, I have each student touch the wires together to ensure that their light bulb lights up.
All the materials used in this lesson are very safe for student use. Students may feel warmth from the battery or wire after they connect all of the wires in their circuit tester.
When each student has completed their circuit tester, I ask them to predict what will happen when we add a variety of objects to the circuit tester.
Next, I ask students to use their circuit tester to test a variety of objects (including straw, marble, pencil, etc.) for conductivity. One of the toughest things for students to manage is sorting out the test materials. To help students achieve independence in the classroom, I create and display a visual organizer showing all of the test materials.
The students connect the loose wires from the battery holder and bulb socket to each object and note whether the light bulb turns on. The students record their results on their conductors and insulators record sheet.
A video of the students testing objects in their circuit testers can be found here.
In this task. students use common objects in a circuit tester to determine whether the object is a conductor or insulator. The students record their results independently or in small groups. The lab includes several objects for which the students may find conflicting results. The pipe cleaner and pencil both can be recorded as conductors or insulators depending on where the student touches the wires to the object. For example, the metal wire in the piper cleaner conducts electricity, but the soft material on the outside does not. Likewise, the graphite in the pencil will conduct electricity, while the wood surrounding it will not. I utilize this conflicting data to discuss the importance of academic honesty and the value of unexpected data. First, I discuss with students that it is critical that they report all scientific results; even those which conflict with their hypothesis. It is only through honest reporting that science can progress. Secondly, I talk with students about the value of conflicting data. I point out that when our class finds contradictory results, it gives us all an opportunity to examine the reasons why this might have occurred. In this lesson, I often have students demonstrate how they got their results by using the materials under the document camera. This highlights to students that it is possible that both groups got valid results and that accurate recording of data can lead to deeper understanding.
I conclude the lesson by adding new vocabulary words to our electricity glossary. I ask students to record the definitions for the terms conductor, insulator, and resistor.