Question

The quantity of heat flowing for $10s$ through a rod of length $40cm$, area $50c{m}^2$ is $200J$. If the temperature difference at the ends of the rod is 80${}^o$C , the coefficient of thermal conductivity of the rod in Wm${}^{-1}$K${}^{-1}$ is:

• A. $20$
• B. $60$
• C. $80$
• D. $120$

Answer 1

The correct option is A $20$

$Q=200$
$A=50\times {10}^{-4}{m}^2$
${\theta }_1={80}^{\circ }C;{\theta }_2=0$
$t=10s;l=0.40m$
$Q=\frac{KA\Delta Tt}{L}$
$200=\frac{K\times 50\times {10}^{-4}\times 80\times 10}{0.4}$
$K=20W/mK$