Question

The two opposite faces of a cubical piece of iron (thermal conductivity = 0.2 CGS units) are at ${100}^{\circ }$ C and $0^{\circ }$ C in ice. If the area of a surface is $4c{m}^2$ , then the mass of ice melted in 10 minutes will be

• A. 30 gm
• B. 300 gm
• C. 5 gm
• D. 50 gm

Answer 1

The correct option is B 300 gm

$Q=mL=KA\frac{({\theta }_1-{\theta }_2)}{l}t\Rightarrow m=\frac{1}{L}\times KA\frac{({\theta }_1-{\theta }_2)}{l}\times t$
$=\frac{1}{80}\times 0.2\times 4\times \frac{(100-0)}{\sqrt{4}}\times 10\times 60$ $(\because l^2=4\Rightarrow l=\sqrt{4})$
$=\frac{0.2\times 4\times 100\times 600}{80\times 2}=300$ gm