Question

Which of the following circular rods (given radius r and length l), each made of the same material and whose ends are maintained at the same temperature will conduct most heat?

• A. $r=r_0;l=l_0$
• B. $r=2r_0;l=l_0$
• C. $r=r_0;l=2l_0$
• D. $r=2r_0;l=2l_0$

Answer 1

The correct option is B $r=2r_0;l=l_0$

Heat is given by $H=KA\Delta {\theta }_x=K\pi r^2\frac{\Delta \theta }{l}$

For option B the value of $H$ will be more.