Question

The diagram shown below represents a slab of conductivity $K$. Find the direction along which the thermal resistance is maximum.

• A. Along $cd$
• B. Along $lm$
• C. Along $ab$
• D. All the directions have equal thermal resistance

Answer 1

The correct option is C Along $ab$

By definition,
Thermal resistance $\left(R\right)=\frac{l}{KA}$
Since, the material is same, $R\propto \frac{l}{A}$
So, $R_{cd}\propto \frac{1}{8};R_{ab}\propto \frac{4}{2};R_{lm}\propto \frac{2}{4}$
$\therefore R_{ab}>R_{lm}>R_{cd}$