Two identical metal wires of


Two identical metal wires of

thermal conductivities $\mathrm{K}_{1}$ and $\mathrm{K}_{2}$ respectively are

connected in series.The effective

thermal conductivity of the combination is:

  1. $\frac{2 \mathrm{~K}_{1} \mathrm{~K}_{2}}{\mathrm{~K}_{1}+\mathrm{K}_{2}}$

  2. $\frac{K_{1}+K_{2}}{2 K_{1} K_{2}}$

  3. $\frac{\mathrm{K}_{1}+\mathrm{K}_{2}}{\mathrm{~K}_{1} \mathrm{~K}_{2}}$

  4. $\frac{\mathrm{K}_{1} \mathrm{~K}_{2}}{\mathrm{~K}_{1}+\mathrm{K}_{2}}$

Correct Option: 1



$\mathrm{R}_{\text {eff }}=\frac{l}{\mathrm{~K}_{1} \mathrm{~A}}+\frac{l}{\mathrm{~K}_{2} \mathrm{~A}}=\frac{2 l}{\mathrm{~K}_{\mathrm{eq}} \mathrm{A}}$

$\mathrm{K}_{\mathrm{eq}}=\frac{2 \mathrm{~K}_{1} \mathrm{~K}_{2}}{\mathrm{~K}_{1}+\mathrm{K}_{2}}$

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