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JEE Main 2021 (17 Mar, Shift 1) · Heat Conduction

Heat Conduction question from JEE Main 2021 (17 Mar, Shift 1)

Q38JEE Main 2021 · 17 MAR · SHIFT 1Medium

Heat Conduction

Two identical metal wires of thermal conductivities K1 and K2 respectively are connected in series. The effective thermal conductivity of the combination is:

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Answer: (a)

Identical wires: same $L$ and $A$ . In series, resistances add: $\frac{2L}{K_{eq}A} = \frac{L}{K_1A} + \frac{L}{K_2A}$
$\frac{2}{K_{eq}} = \frac{1}{K_1} + \frac{1}{K_2}$
$K_{eq} = \frac{2K_1K_2}{K_1+K_2}$ , so the answer is (a).

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