Three rods of same dimensional have thermal conductivity $3 K, 2 K$ and $K$. They are arranged as shown in…

Three rods of same dimensional have thermal conductivity $3 K, 2 K$ and $K$. They are arranged as shown in the figure below
Then, the temperature of the junction in steady state is
  1. $\frac{200}{3}^{\circ} \mathrm{C}$
  2. $\frac{100}{3}{ }^{\circ} \mathrm{C}$
  3. $75^{\circ} \mathrm{C}$
  4. $\frac{50}{3}{ }^{\circ} \mathrm{C}$

Solution

According to the figure $\begin{array}{rlrl} H & =H_1+H_2 \\ \Rightarrow & \frac{3 K A(100-T)}{l} & =\frac{2 K A(T-50)}{l}+\frac{K A(T-0)}{l} \\ \\ 300-3 T =2 T-100+T \\ 6 T =400 \\ \text { or } T =\frac{200}{3}{ }^{\circ} \mathrm{C} \end{array}$

Asked in: AP EAMCET 2009

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