Three conductors of same length having thermal conductivity $\mathrm{k}_1, \mathrm{k}_2$ and $\mathrm{k}_3$ are connected as shown in figure. ![JEE Main 2025 Physics, Thermal Properties of Matter — question figure](https://prepforbharat.s3.ap-south-1.amazonaws.com/exam/615f0e999476412f48314daf/Physics/images/Thermal_Properties_of_Matter/67a2ee89c8b73881fdaea0c0/question_1__q_67a2ee89c8b73881fdaea0c0__cdn-question-pool.getmarks.app__8cFw6o1hSl0e8HAwQ1b0JbnuH7yOn9LqRVhtIk_FYTQ.original.fullsiz__1d7ec29db1_final_ppt_sync.png) Area of cross sections of $1^{\text {st }}$ and $2^{\text {nd }}$ conductor are same and for $3^{\text {rd }}$ conductor it is double of the $1^{\text {st }}$ conductor. The temperatures are given in the figure. In steady state condition, the value of $\theta$ is _______ ${ }^{\circ} \mathrm{C}$. (Given : $\mathrm{k}_1=60 \mathrm{Js}^{-1} \mathrm{~m}^{-1} \mathrm{~K}^{-1}, \mathrm{k}_2=120 \mathrm{Js}^{-1} \mathrm{~m}^{-1} \mathrm{~K}^{-1}, \mathrm{k}_3=135 \mathrm{Js}^{-1} \mathrm{~m}^{-1} \mathrm{~K}^{-1}$ )

![JEE Main 2025 Physics, Thermal Properties of Matter — solution figure](https://prepforbharat.s3.ap-south-1.amazonaws.com/exam/615f0e999476412f48314daf/Physics/images/Thermal_Properties_of_Matter/67a2ee89c8b73881fdaea0c0/solution_1__q_67a2ee89c8b73881fdaea0c0__cdn-question-pool.getmarks.app__tNasaT40DEhUZqJ-YbdIoyHZ68FkDRHeVGwNT3SK9eo.original.fullsiz__d78664cd7f_final_ppt_sync.png) $\begin{aligned} & \mathrm{R}_1=\frac{2 \mathrm{~L}}{\mathrm{~K}_1 \mathrm{~A}} \\ & \mathrm{R}_2=\frac{2 \mathrm{~L}}{\mathrm{~K}_2 \mathrm{~A}} \\ & \mathrm{R}_3=\frac{\mathrm{L}}{\mathrm{K}_3 \mathrm{~A}} \\ & \frac{\theta-100}{\frac{\mathrm{R}_1 \mathrm{R}_2}{\mathrm{R}_1+\mathrm{R}_2}}+\frac{\theta-0}{\mathrm{R}_3}=0 \\ & \theta=40\end{aligned}$

Three conductors of same length… - JEE Main 2025 Physics PYQ

JEE Main 2025 — Physics Thermodynamics

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Three conductors of same length having thermal conductivity $\mathrm{k}_1, \mathrm{k}_2$ and $\mathrm{k}_3$ are connected as shown in figure. JEE Main 2025 Physics, Thermal Properties of Matter — question figure

Area of cross sections of $1^{\text {st }}$ and $2^{\text {nd }}$ conductor are same and for $3^{\text {rd }}$ conductor it is double of the $1^{\text {st }}$ conductor. The temperatures are given in the figure. In steady state condition, the value of $\theta$ is _______ ${ }^{\circ} \mathrm{C}$ . (Given : $\mathrm{k}_1=60 \mathrm{Js}^{-1} \mathrm{~m}^{-1} \mathrm{~K}^{-1}, \mathrm{k}_2=120 \mathrm{Js}^{-1} \mathrm{~m}^{-1} \mathrm{~K}^{-1}, \mathrm{k}_3=135 \mathrm{Js}^{-1} \mathrm{~m}^{-1} \mathrm{~K}^{-1}$ )

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Held on 22 Jan 2025 · Verified 6 Jul 2026.

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JEE Main 2025 Physics, Thermal Properties of Matter — solution figure

$\begin{aligned} & \mathrm{R}_1=\frac{2 \mathrm{~L}}{\mathrm{~K}_1 \mathrm{~A}} \\ & \mathrm{R}_2=\frac{2 \mathrm{~L}}{\mathrm{~K}_2 \mathrm{~A}} \\ & \mathrm{R}_3=\frac{\mathrm{L}}{\mathrm{K}_3 \mathrm{~A}} \\ & \frac{\theta-100}{\frac{\mathrm{R}_1 \mathrm{R}_2}{\mathrm{R}_1+\mathrm{R}_2}}+\frac{\theta-0}{\mathrm{R}_3}=0 \\ & \theta=40\end{aligned}$

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