Q 11-10-025NEETJEE MainEAMCET 2010 (Engineering)Medium
Three rods AB, BC and BD made of the same material and having the same area of cross-section and the same length are joined at B, as in a T-shape. The ends A, C and D are held at temperatures $20°$C, $80°$C and $80°$C respectively. The temperature at the junction B of the three rods is
Answer: (B) $60°$C
Concept. In the steady state the net heat flowing into the junction is zero. Identical rods, so each heat current is proportional to its temperature difference.
Step 1. Balance at B.
$$(80 - \theta) + (80 - \theta) = \theta - 20$$
Step 2. Solve. $3\theta = 180 \Rightarrow \theta = 60°$C.
Answer. $60°$C (Option B).
Solution by Sreeraj P, M.Sc Physics