Question

Two identical rods of copper and iron are coated with wax uniformly. When one end of each is kept at temperature of boiling water the length upto which wax melts are $8.4$ cm and $4,2$ cm, respectively. If the thermal conductivity of copper is $0.92$, then thermal conductivity of iron is

• A. 0.23
• B. 0.46
• C. 0.115
• D. 0.69

Answer 1

The correct option is A 0.23

We know the following relation that $\frac{K_1}{K_2}=\frac{l_1^2}{l_2^2}$
$\frac{\left(0.92\right)}{K_2}=\frac{(8.4{)}^2}{(4.2{)}^2}$
$K_2=0.23$