What term describes a substance that allows electricity to flow freely?

The term that describes a substance allowing electricity to flow freely is "conductor." Conductors are materials, often metals like copper and aluminum, that have electrons that can move easily through the material. This high mobility of charge carriers enables electric current to pass through with minimal resistance.

Materials classified as conductors typically have low resistivity, which means they impede the flow of electric current very little when compared to other types of materials. This property makes them essential for a wide range of electrical applications, such as wires and electronic components, where efficient electricity transmission is crucial.

In contrast, insulators, such as rubber and glass, are materials that do not allow electricity to flow freely due to their tightly bound electrons. Resistors are components specifically designed to limit current flow, and semiconductors have properties that are intermediate between conductors and insulators, enabling them to control electrical flow under certain conditions. Thus, the characteristic of allowing free flow of electricity distinctly identifies conductors among these categories.