What characterizes a good electrical insulator?

A good electrical insulator is characterized by having few free electrons. Insulators are materials that do not allow the flow of electric current easily. This is primarily due to their atomic structure, which does not provide a significant number of free electrons that can move under an electric field. Instead, the electrons in insulating materials are tightly bound to their respective atoms and do not participate in the conduction process.

In contrast, materials with many free electrons are typically good conductors of electricity. These free electrons can move freely through the material, allowing electric currents to flow easily. Additionally, while conducting materials may generate heat when current flows through them (due to resistance), this is not a property that distinguishes insulators.

Overall, the defining quality of an electrical insulator is its ability to resist the flow of electric current, which stems from having a low density of free electrons.