Which of the following is a good electrical insulator?

• A. Copper
• B. Glass
• C. Silver
• D. Aluminum

Answer: (B)

Glass is an excellent electrical insulator due to its molecular structure. Unlike metals such as copper, silver, and aluminum, which have free electrons that allow electricity to flow easily, glass has a very high resistance to the flow of electric current. This low conductivity makes it ideal for use in insulating applications, such as in the construction of electrical components where maintaining separation between conductive parts is essential to prevent short circuits or other electrical failures.

Moreover, the unique properties of glass, such as its ability to withstand high voltages and environmental factors, contribute to its role in electrical insulation. This is particularly important in high-voltage applications and in environments subject to moisture, as glass does not degrade or allow current to flow through it under normal conditions.

In contrast, the other materials listed are known for their good conductivity and are commonly used as conductors in electrical engineering and circuits, which is why they do not qualify as good insulators.