What characteristic makes a good thermal insulator?

What characteristic makes a good thermal insulator?

• A. Low thermal conductivity
• B. High thermal conductivity
• C. High density
• D. Reflective surface

Answer: (A)

A good thermal insulator slows down heat flow, and the key property that controls this is thermal conductivity—the measure of how easily heat can move through a material. Materials with low thermal conductivity resist heat transfer, so they keep warmth in or out effectively. That’s why fiberglass or foam, which trap air and have very low conductivity, are used as insulators. If a material has high thermal conductivity, heat passes through it readily, making it a poor insulator. Density isn’t a reliable indicator by itself, since some dense materials conduct heat well while others with low density can still insulate poorly if there aren’t many barriers to heat flow. Reflective surfaces can reduce radiant heat transfer, but they don’t address conduction in the same way, so they’re not the fundamental criterion for insulation.

A good thermal insulator slows down heat flow, and the key property that controls this is thermal conductivity—the measure of how easily heat can move through a material. Materials with low thermal conductivity resist heat transfer, so they keep warmth in or out effectively. That’s why fiberglass or foam, which trap air and have very low conductivity, are used as insulators. If a material has high thermal conductivity, heat passes through it readily, making it a poor insulator. Density isn’t a reliable indicator by itself, since some dense materials conduct heat well while others with low density can still insulate poorly if there aren’t many barriers to heat flow. Reflective surfaces can reduce radiant heat transfer, but they don’t address conduction in the same way, so they’re not the fundamental criterion for insulation.