Simple Circuits Curriculum

Section 3: Background Information

What Makes a Good Conductor or Insulator?

The nature of the bonds at the atomic level of a material determines whether or not it is a good conductor. Some materials are bonded so that the electrons in their outer shells are very stable. This is true for materials that are ionically or covalently bonded. These do not make good conductors. Instead, they are good insulators. Materials that have metallic bonds have electrons that are free to move about in an electron cloud (not associated with any atom in particular.) These make good conductors.

This lesson invites students to experiment with different materials to see which work as conductors and which do not. Students keep a record of their findings so that they can compare the types of materials that work as conductors and those that work as insulators.

A Passive Causal Variable

Often when we think about causality, we think about agent-oriented causality, where there is a clear actor in a causal relationship—such as electrons causing flow in the circuit. It can be harder to realize the role of variables that are, in some sense, passive. However, as the testing of materials in this lesson indicates, the type of material plays an important role in current flow. Material type is a variable that plays a passive causal role in relation to conduction and insulation. It is analogous to the role that structures like train tracks and bridges play in travel. These things aren't active in their role, but they are critical to the outcome. This lesson alerts students to the fact that the type of material plays a role in current flow.