Three rods of identical cross-section and lengths are made of three different materials of thermal conductivity {K}_{1}, {K}_{2}, and {K}_{3}, respectively. They are joined together at their ends to make a long rod (see figure). One end of the long rod is maintained at 100^\circ{C} and the other at 0^\circ{C} (see figure). If the joints of the rod are at 70^\circ {C} and 20^\circ{C} in steady state and there is no loss of energy from the surface of the rod, the correct relationship between {K}_{1}, {K}_{2} and {K}_{3} is : [6 Sep 2020 Shift 2]

Correct Answer is : K1:K3=2:3; K2:K3=2:5

{K}_{1}: {K}_{3}=2: 3; {K}_{2}: {K}_{3}=2: 5

{K}_{1}: {K}_{2}=5: 2 ; {K}_{1}: {K}_{3}=3: 5

JEE Mains 06-Sep-2020 Shift 2 Solved Paper

Section: Physics

Question : 2 of 75

Marks: +1, -0

Three rods of identical cross-section and lengths are made of three different materials of thermal conductivity K1,K2, and K3, respectively. They are joined together at their ends to make a long rod (see figure). One end of the long rod is maintained at 100°C and the other at 0°C (see figure). If the joints of the rod are at 70°C and 20°C in steady state and there is no loss of energy from the surface of the rod, the correct relationship between K1,K2 and K3 is :

[6 Sep 2020 Shift 2]

K1:K3=2:3; K2:K3=2:5
K1<K2<K3
K1:K2=5:2;K1:K3=3:5
K1>K2>K3

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