Question

If 48 cm of brick and 15 cm of fiberglass have the same R value, then...

both materials have the same density
both materials have the same insulating ability
both materials have the same conducting ability
both materials have the same mass

Answer 1

Explanation:

R-value is defined as thermal resistance divided by the unit area. It shows how an object resists the flow of heat. If the R-value of an object is more, then it means higher resistance i.e. good insulating properties.

R-value depends on

(1) Thickness of material.

(2) The density of a material.

(3) Insulation type.

Here, 24 cm brick and 15 cm fiberglass have the same R-value, it means both materials have the same insulating materials.

So, correct option is (b) "both materials have the same insulating ability".

Answer 2

The r value of a material is that which is related to the amount of heat that can be transferred through it. From the given example above, we say that the amount of heat that can be transferred through 48 cm of brick is the same amount of heat that can be transferred through 15 cm of fiberglass. This means that both substances have the same insulating ability. The answer is the second choice.