What is an insulator?

• A. A material that does not allow heat or electrons to move through it easily.
• B. A material that conducts electricity easily.
• C. A material that stores charge forever.
• D. A metal that easily conducts.

Answer: (A)

An insulator is a material that resists the flow of electric charge and also tends to resist heat transfer. Because it has high electrical resistance, electrons don’t move easily through it, so it prevents current from flowing. This is why insulators are used to cover wires or to keep electric stuff safe to touch. They also act as barriers to heat, so heat doesn’t pass through easily. That matches the idea of a material that does not allow heat or electrons to move through it easily.

The other descriptions describe conductors or ideas that aren’t correct for insulators: a material that conducts electricity easily is a conductor, not an insulator; storing charge forever isn’t a defining property of insulators (they don’t inherently hold charge permanently); and a metal that easily conducts is simply a metal conductor, not an insulator.