Ques. 1JEE Main 2025, 22 January (Morning Shift)
Three conductors of same length having thermal conductivity k1,k2 and k3 are connected as shown in figure. [figure] Area of cross sections of 1st and 2nd conductor are same and for 3rd conductor it is double of the 1st conductor. The temperatures are given in the figure. In steady state condition, the value of is . (Given : k1=60 Js-1 m-1 K-1, k2=120 Js-1 m-1 K-1, k3=135 Js-1 m-1 K-1 )
Answer
40
Solution
Steady state: heat flows like current, H= TR with R= LkA. Rods 1 and 2 are in parallel, in series with rod 3.
[figure]
H1+H2=H3: (k1+k2)A(100- )=k3(2A)
180(100- )=270
=40 C
Answer: 40