1) Consider a pair of insulating blocks with thermal resistances R1 and R2 as shown in the figure. The temperature θ at the boundary between the two blocks is A) θ1θ2√R1R2(θ1+θ2)(R1+R2) B) θ1R1+θ2R2(R1+R2) C) [(θ1+θ2)R1R2](R21+R22) D) (θ1R2+θ2R1)R1+R2 Answer: Option DExplanation:Rate of transmission of heat =TemperaturedifferenceThermalresistance dQdt=dθR Here, dQdt = θ−θ2R2=θ1−θR1 = R1θ−R1θ2 = R2θ1−R2θ θ = (R2θ1+R1θ2)R1+R2