Which is a common insulator?

• A. Rubber
• B. Copper
• C. Ice
• D. Granite

Answer: (A)

An insulator resists the flow of electric current, so electrons don’t move freely through it. Rubber fits this role well because it’s a nonconductive polymer with high resistivity, meaning it doesn’t easily carry electricity. That’s why rubber is widely used to coat and insulate electrical cords, gloves, and equipment—it helps prevent shocks and short circuits.

Copper, on the other hand, is a metal with many free electrons, making it an excellent conductor. Ice can act as an insulator in some contexts but isn’t the typical material used for everyday electrical insulation. Granite isn’t relied on for insulation in electrical systems either. So rubber stands out as the common insulator among these options.