Which of the following is a substance that does not conduct electricity?

The correct answer is that an insulator is a substance that does not conduct electricity. Insulators are materials that restrict the flow of electric current, meaning that they do not allow electrons to move freely. This property makes them essential in various electrical applications, as they prevent unwanted electricity leakage and protect against electrical shock. Common examples of insulators include rubber, glass, and plastic, all of which do not facilitate the movement of electric charges.

Understanding the role of insulators is crucial in electrical systems because they are used to coat wires, enclose components, and provide safety in electrical installations. In contrast, conductors are materials that easily allow the flow of electricity, while transistors are semiconductor devices used for amplification and switching in electronic circuits. Generators convert mechanical energy into electrical energy, and while they play a significant role in electricity generation, they do not define the concept of conductivity in materials.