Question

The ratio of thermal conductivities of two rods of different material is 5 : 4. The two rods of same area of cross-section and same thermal resistance will have the lengths in the ratio–

• A. 4 : 5
• B. 9 : 1
• C. 1 : 9
• D. 5 : 4

Answer 1

Answer: (D)

5 : 4

Answer 2

$\frac{L_{1}}{K_{1}A}$ = $\frac{L_{2}}{K_{2}A}$

$\frac{K_{1}}{K_{2}}$ = $\frac{L_{1}}{L_{2}}$