Question

The ratio of thermal conductivity 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. 4:05
• B. 9:01
• C. 1:09
• D. 5:04

Answer 1

Answer: (D)

5:04

Answer 2

Using the relation $\frac{{{K}_{1}}{{A}_{1}}}{{{d}_{1}}}=\frac{{{K}_{2}}{{A}_{2}}}{{{d}_{2}}}$ (Here: ${{A}_{1}}={{A}_{2}}$ ) So, $\frac{{{d}_{1}}}{{{d}_{2}}}=\frac{{{K}_{1}}}{{{K}_{2}}}\frac{{{A}_{1}}}{{{A}_{2}}}=\frac{5}{4}$