ARRL Technician Practice Exam

Which of the following is a good electrical insulator?

1. Copper

2. Glass

3. Aluminum

4. Silver

The correct answer is: Glass

Glass is considered a good electrical insulator due to its atomic structure. In insulators, atoms are tightly bound, which prevents the flow of electricity. Glass, being a non-metal, has a high resistivity, meaning it does not easily allow the movement of electrical charges. This makes it an effective barrier against electricity, which is why it is used in various applications where insulation from electrical currents is required, such as insulating wires or in electrical components. In contrast, materials like copper, aluminum, and silver are excellent conductors of electricity. They have free electrons that allow for the easy flow of electrical current, making them unsuitable for insulation purposes. Understanding the properties of different materials is crucial when learning about electrical circuits and safety.