ℓ1(T1−T)k1=ℓ2(T−T2)k2 T=k1ℓ2+k2ℓ1T1k1ℓ2+T2k2ℓ1
JEE Main 2007 — Physics Thermodynamics
One end of a thermally insulated rod is kept at a temperature T1 and the other at T2. The rod is composed of two sections of lengths ℓ1 and ℓ2 and thermal conductivities k1 and k2 respectively. The temperature at the interface of the two sections is 
Held on 30 Apr 2007 · Verified 6 Jul 2026.
(k2ℓ2T1+k1ℓ1T2)/(k1ℓ1+k2ℓ2)
(k2ℓ1T1+k1ℓ1T2)/(k2ℓ1+k1ℓ2)
(k1ℓ2T1+k2ℓ1T2)/(k1ℓ2+k2ℓ1)
(k1ℓ1T1+k2ℓ2T2)/(k1ℓ1+k2ℓ2)
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10 mole of an ideal gas is undergoing the process shown in the figure. The heat involved in the process from $P_{1}$ to $P_{2}$ is $\alpha$ Joule ($P_{1}=21.7 \mathrm{~Pa}$ and $\left.P_{2}=30 \mathrm{~Pa}, \mathrm{C}_{v}=21 \mathrm{~J} / \mathrm{K}. \mathrm{mol}, R=8.3 \mathrm{~J} / \mathrm{mol}. \mathrm{K}\right)$. The value of $\alpha$ is $\_\_\_\_$. 
Heat is supplied to a diatomic gas at constant pressure. Then the ratio of $\Delta Q : \Delta U : \Delta W$ is _______.
The r.m.s. speed of oxygen molecules at $47^{\circ} \mathrm{C}$ is equal to that of the hydrogen molecules kept at $\_\_\_\_$ ${ }^{\circ} \mathrm{C}$. (Mass of oxygen molecule/mass of hydrogen molecule $=32 / 2$)
Rods $x$ and $y$ of equal dimensions but of different materials are joined as shown in figure. Temperatures of end points $A$ and $F$ are maintained at $100^{\circ} \mathrm{C}$ and $40^{\circ} \mathrm{C}$ respectively. Given the thermal conductivity of $\operatorname{rod} x$ is three times of that of $\operatorname{rod} y$, the temperature at junction points $B$ and $E$ are (close to): 
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Statement I: Change in internal energy of a system containing $n$ mole of ideal gas can be written as $\Delta U = n C_v (T_f - T_i) = \dfrac{nR}{\gamma - 1}(T_f - T_i)$, where $\gamma = \dfrac{C_p}{C_v}$, $T_i =$ initial temperature, $T_f =$ final temperature. Statement II: Relation between degree of freedom $f$ and $\gamma (= C_p/C_v)$ is $\left(\gamma = 1 + \dfrac{2}{f}\right)$ Choose the correct answer from the options given below
Work through every JEE Main Thermodynamics PYQ, year by year.