Question

Five identical rods are joined as shown in figure. Point A and C are maintained at temperature ${120}^{\circ }C$ and ${20}^{\circ }C$, respectively. The temperature of junction B will be

• A. ${100}^{\circ }C$
• B. ${80}^{\circ }C$
• C. ${70}^{\circ }C$
• D. $0^{\circ }C$

Answer 1

The correct option is C ${70}^{\circ }C$

Let the temperature of junction $B$ is ${\theta }^{\circ }\text{C}$.
If thermal resistance of each rod is considered $R$, then the given combination can be redrawn as follows:


$(\text{Heat current}{)}_{AC}=({\text{Heat cureent}}_{AB})$
$\frac{(120-20)}{2R}=\frac{(120-\theta )}{R}\Rightarrow \theta ={70}^{\circ }C$