The coefficient of thermal conductivity of copper is 9 times that of steel. In the composite cylindrical bar shown in the figure, what will be the temperature at the junction of copper and steel?

Step-by-step solution

The given situation is shown below Thermal conductivity of copper =9 thermal conductivity of steel K_ c =9 K_ s Since, both bar are connected in series, hence heat current along the bar will be same. i. e d Q d t = K_ e ~A (T₁-T ) l₁ = K_ s A (T-T₂ ) l₂ 9 K_ S A(100-T) 18 = K_ s A(T-0) 6 3(100-T)=T300-3 T=T 4 T=300 T=75^ C