K1(100−70)=K2(70−20)=K3(20−0)
K130=K2(50)=K3(20)
⇒K1:K2:K3=10:6:15
K1:K3=2:3
Three rods of identical cross-section and length are made of three different materials of thermal conductivity K_1,K_2 and K_3, respectively. They…
JEE Main 2020 — Physics Thermodynamics
2020mcqmedium
Three rods of identical cross-section and length 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 and there is no loss of energy from the surface of the rod, the correct relationship between K1,K2 and K3 is :
Official previous-year question
Held on 6 Sept 2020 · Verified 6 Jul 2026.
Options
- A
K1:K3=2:3,
K2:K3=2:5
- B
K1<K2<K3
- C
K1:K2=5:2,
K1:K3=3:5
- D
K1>K2>K3
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