GATE 2025 AG – Question 35
Three identical metal wires AC, BC, CD have equal length, diameter and thermal conductivity. Heat flows from A and B to C and from C to D. A and B are at 100°C, D at 40°C. With steady conduction and no heat loss, find C’s temperature in integer °C.
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Correct answer: 80 to 80
Explanation
Each wire has the same thermal conductance $G=kA/L$. Energy balance at C gives $G(100-T_C)+G(100-T_C)=G(T_C-40)$. Cancel G and solve $200-2T_C=T_C-40$,so $3T_C=240$. Therefore **80°C**. The two hot branches act in parallel.