Question

The coefficient of thermal conductivity of copper, mercury and glass are respectively $K_C,K_m$ and $K_g$ such that $K_c>K_m>K_g$. If the same quantity of heat is to flow per second per unit area of each and corresponding temperature gradients are $X_C,X_m$ and $X_g$, then

• A. $X_c=X_m=X_g$
• B. $X_c>X_m>X_g$
• C. $X_c<X_m<X_g$
• D. $X_m<X_c<X_g$

Answer 1

The correct option is C $X_c<X_m<X_g$

We know that, rate of heat transfer
$q=-KA\frac{dT}{dx}$

Given that, $\frac{q}{A}=\text{constant}$
$\therefore$ Temperature gradient $\frac{dT}{dx}\propto \frac{1}{K}$
Since, $K_c>K_m>K_g$ we can interpret that $X_c<X_m<X_g$