Question

Which of the following cylindrical rods will conduct most heat, when their ends are maintained at the same steady temperature

• A. Length 1 m; radius 1 cm
• B. Length 2 m; radius 1 cm
• C. Length 2 m; radius 2 cm
• D. Length 1 m; radius 2 cm

Answer 1

Answer: (D)

Length 1 m; radius 2 cm

Answer 2

$\frac{Q}{t} = \frac{KA\Delta\theta}{l}$⇒ $\frac{Q}{t} \propto \frac{A}{l} \propto \frac{r^{2}}{l}$

$\because$ $\frac{r^{2}}{l}$ is maximum in option (4), hence it will conduct more heat.