JEE PYQ: Thermal Properties Of Matter Question 3
Question 3 - 2021 (17 Mar 2021 Shift 1)
Two identical metal wires of thermal conductivities $K_1$ and $K_2$ respectively are connected in series. The effective thermal conductivity of the combination is:
(1) $\frac{2K_1 K_2}{K_1 + K_2}$
(2) $\frac{K_1 + K_2}{2K_1 K_2}$
(3) $\frac{K_1 + K_2}{K_1 K_2}$
(4) $\frac{K_1 K_2}{K_1 + K_2}$
Show Answer
Answer: (1)
Solution
$R_{eff} = \frac{l}{K_1 A} + \frac{l}{K_2 A} = \frac{2l}{K_{eq} A}$, so $K_{eq} = \frac{2K_1 K_2}{K_1 + K_2}$
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