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
Medium
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(d) Given ${A_1} = {A_2}$ and $\frac{{{K_1}}}{{{K_2}}} = \frac{5}{4}$
$\because$${R_1} = {R_2} $ $\Rightarrow \frac{{{l_1}}}{{{K_1}A}} = \frac{{{l_2}}}{{{K_2}A}}$
==> $\frac{{{l_1}}}{{{l_2}}} = \frac{{{K_1}}}{{{K_2}}} = \frac{5}{4}.$
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