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Two rods having thermal conductivity in the ratio of 5:3 having equal lengths and equal cross-sectional area are joined end to end. If the temperature of the free end of the first rod is 100°C and free end of the second rod is 20°C, then the temperature of the junction is?

Two rods having thermal conductivity in the ratio of 5:3 having equal lengths and equal cross-sectional area are joined end to end. If the temperature of the free end of the first rod is 100°C and free end of the second rod is 20°C, then the temperature of the junction is? Correct Answer 70°C

Let T be the temperature of the junction. In the steady state, Q1/t=Q2/t (K1 A(100-T))/d=(K2 A(T-T2))/d 5(100-T)=3(T-20) 8T=560 or T=70°C.

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