JEE Main 2022 · 24 Jun · Shift 1 · Physics Q50

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Two metallic blocks $M_1$ and $M_2$ of same area of cross-section are connected to each other (as shown in figure). If the thermal conductivity of $M_2$ is $K$ then the thermal conductivity of $M_1$ will be :

[Assume steady state heat conduction]

Two blocks in series: M1 (length 16 cm) with its free end at 100°C, joined to M2 (length 8 cm) whose free end is at 0°C; the junction is at 80°C.

10 K

8 K

12.5 K

2 K

Answer and worked solution

Official answer: B

Same heat current in series. $\dfrac{K_1A(100-80)}{16}=\dfrac{KA(80-0)}8$ .

Solve. $\dfrac{20K_1}{16}=10K$ , so $K_1=8K$ .

(B)

Topics:Conduction

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JEE Main 2022 · 24 Jun · Shift 1, Physics question 50