Rubber, wood, and plastic are examples of

• A. Insulators
• B. Semiconductors
• C. Conductors
• D. Alloys

Answer: (A)

Electrical insulation is the key idea here: some materials resist the flow of electricity. Rubber, wood, and plastic fit this role because they have high resistivity and few free electrons, so electric charges don’t move through them easily. That’s why they’re used to insulate wires and devices to prevent shocks. They’re not conductors, which readily pass current; they aren’t semiconductors, which have intermediate conductivity; and they aren’t alloys, which are metal mixtures that typically conduct electricity.