# In the figure ABC is a conducting rod whose lateral surfaces are insulated. The length of the section AB is one-half of that of BC, and the respective

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In the figure ABC is a conducting rod whose lateral surfaces are insulated. The length of the section AB is one-half of that of BC, and the respective thermal conductivities of the two sections are as given in the figure. If the ends A and C are maintained at 0^(@)C and 70^(@)C respectively, the temperature of junction B in the steady state is

A. 30^(@)C
B. 40^(@)C
C. 50^(@)C
D. 60^(@)C

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Correct Answer - A
Heat current in both the rods are equal
or H_(CB) = H_(BA)
or (theta_(C)-theta_(B))/(2l//3KA)=(theta_(B)-theta_(A))/(l//2KA)
therefore 3/2(70-theta_(B))= 2(theta_(B)-0)
or theta_(B) = 30^(@)C

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