Physics

Problem

Which one of the following expressions gives the thermal resistance

R

of a slab of thickness

L

, cross-sectional area

A

and thermal conductivity

k

? a)

\displaystyle \frac{2L}{kA}

\displaystyle \frac{L}{k}

\displaystyle \frac{L}{kA}

\displaystyle \frac{L}{2kA}

Intuitive explanation

Thermal resistance is the material's opposition to heat flow—think of it as the thermal analog of electrical resistance. Just as electrical resistance increases with length and decreases with cross-sectional area, thermal resistance follows the same pattern: thicker slabs resist heat more, while larger areas let heat flow more easily. The key is recognizing that $R$ is inversely proportional to conductivity $k$ and area $A$ , but directly proportional to thickness $L$ .

Intuitive explanation

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