Question

Six identical conducting rods are joined as shown in figure. Points A and D are maintained at ${200}^{\circ }$C and ${20}^{\circ }$C respectively. The temperature of junction B wilI be

• A. ${120}^{\circ }$C
• B. ${100}^{\circ }$C
• C. ${140}^{\circ }$C
• D. ${80}^{\circ }$C

Answer 1

Answer: (C)

${140}^{\circ }$C

If the term $\Delta T$ is compared with potential and power radiated with current then the resistance of each will be $\frac{l}{kA}$

Then each rod can be replaced with a resistor of resistance $R=\frac{l}{kA}$

Then the net resistance if $3R=\frac{3l}{kA}$

Potential drop between the adjacent points are same.

So the temperature is $200-\frac{200-20}{3}={140}^{o}C$