Six identical conducting rods are joined as shown in figure. Points A and D are maintained at temperatures 200oC and 20oC, respectively. The temperature of junction B will be

Let the thermal resistance of each rod be R.The two resistances connected along two paths from B to C are equivalent to 2R each and their parallel combination is R. Effective thermal resistance between B and D = 2R  Temperature of interface θ=R1θ2+R2θ1R1+R2θ=R×20+2R×200R+2R=4203=140∘C