Q. 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 $2\ cm$
Explanation
(d) $\frac{Q}{t} = \frac{KA\ \mathrm{\Delta}\theta}{l} \Rightarrow \frac{Q}{t} \propto \frac{A}{l} \propto \frac{r^{2}}{l}$
$\because\frac{r^{2}}{l}$ is maximum in option (d), hence it will conduct more heat
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.